Dating of pregnancy ppt
A pregnancy that lasts more than 42 weeks days since the first day of the last menstrual period is considered post-term. The vast majority of women deliver between 37 and 42 weeks of pregnancy. It is not known why some women carry a pregnancy longer than others. It is often due to a miscalculation of pregnancy conception dates. A woman is much more likely to have a post-term pregnancy if previous pregnancies went beyond 42 weeks. Post-term pregnancy is associated with longer labors and operative delivery forceps or vacuum-assisted birth.
Mothers are at increased risk for vaginal birth trauma due to a large baby. Cesarean delivery is twice as likely in a post-term pregnancy because of the size of the baby. Mothers are also at increased risk for infection and wound complications, and postpartum after birth hemorrhage.
Ultrasound for fetal assessment in early pregnancy
There are also risks for the fetus and newborn in a post-term pregnancy, including stillbirth and newborn death. Toward the end of pregnancy, the placenta, which supplies the fetus with the nutrients and oxygen from the mother's circulation, begins to age and may not function as efficiently as before. Amniotic fluid volume may decrease and the fetus may stop gaining weight, or may even lose weight. Risks can increase during labor and birth for a fetus with poor oxygen supply. Routine early pregnancy scanning in this group may impact on accuracy of assignment of chorionicity in multiple pregnancies, as some studies have shown that this can be done more accurately at earlier gestations Lee It is also possible that earlier diagnosis of multiple pregnancy will occur with routine early pregnancy scanning, thus preventing inappropriate maternal serum screening Persson ; Saari-Kemppainen In a systematic review, based on 11 studies one randomised controlled trial, six retrospective cohorts and four prospective cohorts undertaken to examine the use of routine second trimester ultrasound to detect fetal anomalies, the overall prevalence of fetal anomaly was 2.
Using late pregnancy ultrasound scanning overall, detection of fetal anomaly was Optimum timing of such ultrasound scans may be aided by accurate estimation of dates using routine early pregnancy scanning. A recent Cochrane review concluded that a policy of labour induction after 41 completed weeks or later compared to awaiting spontaneous labour either indefinitely or at least one week is associated with fewer perinatal deaths Gulmezoglu It is possible that routine early pregnancy scanning will improve the accuracy of pregnancy dating and thereby affect the number of pregnancies undergoing induction for post-maturity.
Whilst there is evidence to suggest that ultrasound is very attractive to women and families, studies have also shown that women often lack information about the purposes for which an ultrasound scan is being done and the technical limitations of the procedure Bricker a. It is therefore essential that patient satisfaction is considered. The use of routine pregnancy ultrasound needs to be considered in the context of potential hazards. In theory, some ultrasonic energy propagated through tissue is converted to heat, and in laboratory experiments, biological effects of ultrasound have been observed.
In the clinical setting, diagnostic ultrasound uses pulsed waves short pulses of sound propagation , and most modern machines are designed so that safe power output limits cannot be exceeded. One of the aims of this review is to assess available data and determine whether clear epidemiological evidence exists from clinical trials that ultrasound examination during pregnancy is harmful.
All published, unpublished, and ongoing randomised controlled trials with reported data that compared outcomes in women who experienced routine early pregnancy ultrasound with outcomes in women who experienced the selective use of early pregnancy ultrasound. We have included quasi-randomised controlled trials. We planned to include trials reported as abstracts provided that they contained sufficient information for us to assess eligibility and risk of bias, and that results were described in sufficient detail.
Women with early pregnancies, i. Routine ultrasound examination compared with selective ultrasound examination. Trials identified through the searching activities described above are each assigned to a review topic or topics. The Trials Search Co-ordinator searches the register for each review using the topic list rather than keywords. We examined cited references, abstracts, letters to the editor, and editorials for additional studies. Where necessary, we contacted the primary investigator directly to obtain further data.
We assessed for inclusion all potential studies identified as a result of the search strategy. We resolved any disagreement through discussion. We designed a form to extract data. Two of the review authors independently extracted data for each included study using the agreed form. We resolved discrepancies through discussion. We used the Review Manager software RevMan to enter data, and after data entry we checked tables for accuracy.
When information regarding any of the above was unclear, we attempted to contact authors of the original reports to provide further details. Two review authors independently assessed risk of bias for each study using the criteria outlined in the Cochrane Handbook for Systematic Reviews of Interventions Higgins We resolved any disagreement by discussion or by involving a third assessor.
We have described for each included study the method used to generate the allocation sequence. We have described for each included study the method used to conceal the allocation sequence and considered whether group allocation could have been foreseen in advance of, or during recruitment, or changed after assignment. With an intervention such as ultrasound it may not be feasible to blind study participants and personnel from knowledge of which intervention a participant received. In studies where both groups received ultrasound but results were not revealed for the control group, blinding participants may be possible, but staff are still likely to be aware of group allocation.
We have provided information on whether blinding or partial blinding was attempted and assessed whether the intended blinding was effective. We have described for each included study, and for each outcome or class of outcomes, the completeness of data including attrition and exclusions from the analysis. We have noted whether attrition and exclusions were reported, the numbers included in the analysis at each stage compared with the total randomised participants , reasons for attrition or exclusion where reported, and whether missing data were balanced across groups or were related to outcomes.
Where sufficient information was reported or supplied by the trial authors, we have re-included missing data in the analyses. We have assessed methods for dealing with missing data in the included studies as:. We have described for each included study how the possibility of selective outcome reporting bias was examined by us and what we found. We have described for each included study any important concerns we had about other possible sources of bias such as baseline imbalance between groups.
We assessed whether each study was free of other problems that could put it at risk of bias:. We have made explicit judgements about whether studies are at high risk of bias, according to the criteria given in the Handbook Higgins With reference to 1 to 6 above, we have discussed the likely magnitude and direction of the bias and whether we consider it is likely to impact on the findings.
For continuous data, we have used the mean difference if outcomes are measured in the same way between trials. We have used the standardised mean difference to combine trials that measure the same outcome, but using different methods. Cross-over designs are unlikely to be appropriate for trials in pregnancy and childbirth and we have not included them. We are aware of potential variations in units of analysis across trials. We planned to include cluster-randomised trials in the analyses along with individually randomised trials.
If such trials are identified in the future, we will adjust their standard errors using the methods described in Gates and Higgins using an estimate of the intracluster correlation co-efficient ICC derived from the trial if possible , or from another source. If we use ICCs from other sources, we will report this and conduct sensitivity analyses to investigate the effect of variation in the ICC.
If we identify both cluster-randomised trials and individually randomised trials, we plan to synthesise the relevant information. We will consider it reasonable to combine the results from both if there is little heterogeneity between the study designs and the interaction between the effect of intervention and the choice of randomisation unit is considered to be unlikely. We will also acknowledge heterogeneity in the randomisation unit and perform a separate meta-analysis. Therefore, we will perform the meta-analysis in two parts as well.
For included studies, we have noted levels of attrition. We planned to explore the impact of including studies with high levels of missing data in the overall assessment of treatment effect by using sensitivity analysis. For all outcomes we carried out analyses, as far as possible, on an intention-to-treat basis, i. The denominator for each outcome in each trial was the number randomised minus any participants whose outcomes were known to be missing. We examined the forest plots for each analysis to look for signs of heterogeneity between studies, and used the I 2 statistic to quantify heterogeneity among the trials in each analysis.
In analyses where random-effects analyses have been used, the overall treatment effect represents an average. Where there are moderate or high levels of heterogeneity, we would advise readers to interpret results cautiously. We have carried out statistical analysis using the Review Manager software RevMan If we suspected any differences between subgroups we planned to seek statistical advice.
We have carried out sensitivity analysis to explore the effect of trial quality on study results. We planned to exclude from the analysis trials assessed as having inadequate or unclear allocation concealment or high levels of attrition in order to assess whether this would make any substantive difference to the overall results. We assessed possible publication bias by visually examining the funnel plots for those outcomes where at least 10 studies contributed data, with funnel plot asymmetry indicating possible publication bias.
Characteristics of included studies ; Characteristics of excluded studies ; Characteristics of studies awaiting classification. The search strategy identified 63 papers reporting findings from 24 studies examining ultrasound for fetal assessment in early pregnancy most studies resulted in several publications or reports. We have included 11 trials in the review and one study is awaiting further assessment Newcastle.
In addition, one of the included studies Norway reported long-term, childhood outcome data from two of the included trials Alesund ; Trondheim We excluded 11 studies. The studies were carried out in a number of countries: The earliest trials began recruitment in the late s Alesund ; Trondheim All of the trials included an intervention involving an ultrasound examination before the 24th week of pregnancy.
The dates of the scans, and the number of scans women received varied in different trials. The gestational age at which index scans were performed, and the purpose of scans, varied in different trials. In the Adelaide , study scans in the intervention group were carried out at between 11 and 14 weeks. The purposes of the scan were to ascertain gestational age with the aim of improving the timing of other screening tests , identify multiple pregnancies, and to carry out a limited examination of fetal morphology.
In the two Norwegian studies, women in the intervention group were offered two scans, the first at 18 to 20 weeks and then a late ultrasound scan at 32 weeks Alesund and Trondheim with follow-up data for both studies reported in the Norway papers. The purposes of the early scan were to measure biparietal diameter BPD ; to estimate the expected date of delivery EDD ; to identify multiple pregnancies; to note the location of the placenta; and to carry out a general examination of the fetus. The ultrasound in the intervention group of the Helsinki trial was carried out between 16 and 20 weeks; the aims were similar to those in the Norwegian trials, with the amount of amniotic fluid also being recorded.
In the Missouri trial, scans generally took place between 10 to 12 weeks up to 18 weeks and were carried out to estimate gestational age, identify multiple pregnancies, assess fetal viability and to identify uterine abnormalities. The Sweden study had similar aims; women attending 19 antenatal clinics in Stockholm were invited for a scan at 15 weeks range 13 to 19 weeks intervention or received selective scans after 19 weeks control.
In the Oxford study, women in both the intervention and control groups had routine scans at 18 to 20 weeks, in addition women in the intervention group were offered an early scan at between eight and 12 weeks to estimate gestational age. The purpose of the earlier scan was to identify the location of the placenta, the volume of amniotic fluid, uterine abnormalities, multiple pregnancies, BPD and other measures of fetal size, and a detailed assessment of fetal anatomy. In the South African study Tygerberg , a single scan was offered to women in the intervention group; women received a scan which aimed to ascertain gestational age and to identify major fetal anomalies.
Finally, in the Johannesburg trial, scans in the intervention group were carried out between 18 and 23 weeks; the reasons for scans were not described. Further details of settings, participants and interventions are set out in the Characteristics of included studies tables. In four of the excluded studies all participants in both the intervention and control groups received early scans; in the studies by Saltvedt and Schwarzler , the timing of scans was examined i.
In the trial by Bennett , the focus was specifically on the timing of the assessment of gestational age with scans in the first and second trimesters. In the trial by Larsen , the participants were high-risk women, with those in the intervention group receiving an additional scan at 28 weeks. Two trials compared two versus three or four dimensional ultrasound scans Leung ; Rustico In the Hong Kong study, women in both arms of the trial had two routine scans, in the intervention group the earlier scan was more detailed than in the control group.
The study by Belanger did not include results relevant to the outcomes of the review. We attempted to contact the authors of one report, but results were not available Wald In the majority of the included studies, no information was provided on the methods used to generate the sequence for randomisation. In the Adelaide study, a table of random numbers was used to generate the allocation order, and in the RADIUS study the sequence was determined by a computerised random number generator.
In two studies there was balanced block randomisation Missouri block size four and Oxford block size six. In the Trondheim study outcome assessment was described as partially blinded.
In the London study the results of the scan for the control group were not stored in case notes and therefore not available to outcome assessors although outcome assessors would be aware of group allocation by the presence or absence of the scan report. The lack of blinding in these studies is unlikely to affect some review outcomes such as perinatal mortality but outcomes relying on clinical judgement e. There was relatively high attrition in the Johannesburg trial; We have attempted to use consistent denominators in the analyses within this review.
For pregnancy and early postnatal outcomes we have tried to include all women randomised less: We have included women lost to follow up for other reasons e. In some cases it was difficult to determine the denominators, as detailed information on attrition at different stages was not reported in the Johannesburg study it was not clear how many women were randomised to each study group, and so we had to use the group denominators for those women available to follow up.
Again, it was not always easy to ascertain the appropriate denominators for babies. For long-term follow up where there was greater attrition for example, there was complete data for approximately half of the original sample for some outcomes at childhood follow up in the Sweden study , we have used the denominators reported by the authors in study publications. We will return to this issue in the discussion. Some of the trials had other potential sources of bias: While not a source of bias as such, large numbers of women were not eligible for inclusion in the RADIUS trial and this may affect the generalisability of results.
Failure to detect multiple pregnancies by 24 weeks was reported in seven studies. It was more likely that multiple pregnancies would not be detected by 24 weeks in the unscreened groups; only two of multiple pregnancies were undetected at 24 weeks in the screened groups, compared with 56 of in the control groups RR 0. Compared with controls, women offered early routine ultrasound were less likely to be induced for post-maturity.
For this outcome there was a high level of heterogeneity between studies. A visual examination of the forest plot reveals that the general direction of findings is the same among studies; however, the size of the treatment effect and the rates of induction in control groups vary.
We used a random-effects model in the meta-analysis and the average treatment effect favoured the screened group RR 0. There was no evidence of a significant difference between the screened and control groups for perinatal mortality unweighted percentages 0. When lethal malformations were excluded, rates of perinatal death in the screened and unscreened groups were very similar 0.
All multiple pregnancies were detected before labour in the intervention groups, whereas 12 of the in the control groups remained undetected at the onset of labour RR 0.
Screened groups were also more likely to have major fetal anomalies detected before birth RR 3. There was no evidence of significant differences between groups in terms of the number of low birthweight babies less than g or very low birthweight babies less than g ; for these outcomes, some studies reported results for singletons only, and so in the analyses we have set out results for singletons and all babies separately; Analysis 1.
There was no evidence of statistically significant differences between groups in the number of babies that were small for gestational age, or in mean birthweight Analysis 1. There were high levels of heterogeneity for outcomes relating to low birthweight, and these results should be interpreted with caution.
The number of babies with low Apgar scores seven or less at five minutes was similar in the two groups, and there was no difference in rates of admission to neonatal intensive care Analysis 1. In three studies babies were followed up into childhood results for children up to nine years in the Alesund and Trondheim trials are reported together in the Norway study, and the Sweden study includes data for children at eight to nine years and for teenagers aged 15 to 16 years.
For children aged eight to nine years, there were no significant differences for any of the outcomes reported including school performance, hearing and vision, disabilities or dyslexia which was measured in a subset of the main sample Analysis 1. There was concern raised regarding an excess of non-right handedness in the intervention group in the Norwegian study; however, the Swedish study did not confirm these findings, and results may have occurred by chance.
Examination of the school records of teenagers aged 15 to 16 years revealed little difference in the performance of children whose mothers had been randomised to ultrasound or no ultrasound in the Swedish trial. Authors reported that there was no strong evidence of differences between groups for school performance grades over all subjects for girls or boys. For physical education there was a small difference in scores for boys; those whose mothers had been randomised to the ultrasound group had slightly lower mean scores compared to those in the control group, but this finding was not statistically significant.
It was more likely that women would undergo pregnancy termination for fetal abnormality in the screened groups, although overall the number of terminations was small 24 of 14, pregnancies in screened groups were terminated after detection of abnormality compared with 10 of 14, in controls RR 2.
There was no significant evidence that ultrasound was associated with reduced numbers of women undergoing delivery by caesarean section Analysis 1. Overall, on average, there were slightly fewer inductions of labour for any reason, including post-maturity in women in the screened groups; in view of heterogeneity we used a random-effects model for this outcome RR 0. The rate of induction in the screened group was The Adelaide trial examined whether an early scan would reduce the number of serum screening tests or fetal anomaly scans that needed to be repeated because they had been performed at the wrong gestational age.
There was no significant evidence that the numbers of women having repeat testing was reduced in the intervention group Analysis 1. There was also no significant evidence in the Helsinki and Johannesburg trials that the number of antenatal visits was reduced Analysis 1. In the Adelaide study investigators examined whether having an early scan was reassuring or worrying to mothers.
Fewer mothers in the screened group reported feeling worried about their pregnancies RR 0. The impact of screening on costs to women and health services was examined in two trials. The cost to health services was not simple to calculate; the cost of the examinations was offset by fewer hospital visits and stays, and in this study there was a lower perinatal mortality rate and increased pregnancy termination in the screened group, leading the authors to conclude that ultrasound resulted in cost savings Leivo The issue of cost was also examined in a trial carried out in a low-resource setting where overall adverse fetal outcome was higher, but where fetal anomalies represented a smaller proportion of adverse outcomes compared with high resource settings.
An explicit aim of the Tygerberg study was to examine whether the costs of routine ultrasound for all women rather than selective ultrasound would be offset by a reduction in the use of other healthcare resources. In this study routine ultrasound was perceived as being an expensive luxury: Included studies did not report data for a number of the secondary outcomes pre-specified in the review protocol including the detection of ectopic pregnancy or chorionicity of multiple pregnancy, laparoscopic management of ectopic pregnancy and surgical management of abortion.
We planned subgroup analysis by parity, by the timing of the early ultrasound before or after 14 weeks and by whether the control group had scans with results concealed rather than selective scans. We examined subgroups for primary outcomes only. Information on parity was not available for us to be able to carry out this analysis. In the Adelaide study, scans were planned for 11 to 14 weeks, in Oxford 10 to 12 weeks, and in Missouri , while scans could be performed up to 18 weeks, most were carried out between 10 and 12 weeks.
There were no clear differences in outcomes in groups where scans were performed earlier rather than later for induction for post-term pregnancy, detection of multiple pregnancy or perinatal death Analysis 1. In one study, women in both groups were screened but results were revealed for the intervention group only London There was considerable overlap in the confidence intervals for these outcomes for the London study and the other trials, suggesting no clear differences between subgroups.
Two studies used a quasi-randomised design case note number London allocation by day of the week Johannesburg ; removing these studies from the analysis did not affect overall results for the primary outcomes. Only one outcome perinatal death included data from ten studies Analysis 1. Considerable caution needs to be exercised in interpreting the results of aspects of this review in view of the fact that there is considerable variability in both the timing of the intervention and the number of scans which women received during pregnancy.
The assumed benefits of routine ultrasonography in early pregnancy have been: These assumptions appear to have been justified by analysis of data from the studies included in this review. However, the high levels of heterogeneity for the former outcome means caution should be applied. The detection of fetal malformation has been addressed in detail only in two of the trials. The Helsinki trial showed improved detection with a resultant increase in the termination of pregnancy rate and a drop in perinatal mortality. There were, however, large differences in the detection rates between the two hospitals involved in this study, which shows that variation in skill and expertise can impact on performance and effectiveness of ultrasonography, and highlights the need for education, training, audit and quality control.
Based on the Helsinki trial results and other reports of observational data, this implies unsatisfactory diagnostic expertise. A combination of low detection rates of malformation, together with a gestational age limit of 24 weeks for legal termination of pregnancy in the RADIUS trial, produced minimal impact on perinatal mortality, unlike the Helsinki experience.
The majority of obstetric units in the developed world already practice routine early pregnancy ultrasonography. For those considering its introduction, the benefit of the demonstrated advantages needs to be considered against the theoretical possibility that the use of ultrasound during pregnancy could be harmful, and the need for additional resources. At present, there is no clear evidence that ultrasound examination during pregnancy is harmful.
The findings from the follow up of school children and teenagers, exposed as fetuses to ultrasound in the Norwegian and Swedish trials Norway ; Sweden are generally reassuring; the finding that fewer children in the Norwegian ultrasound groups were right-handed was not confirmed by intention to treat analysis of long-term follow-up data from the Swedish trial. The Norwegian finding is difficult to interpret and may have been a chance observation that emanated from the large number of outcome measures assessed, or from the method of ascertainment.
Alternatively, if it was a real consequence of ultrasound exposure, then it could imply that the effect of diagnostic ultrasound on the developing brain may alter developmental pathways. No firm conclusion can be reached from available data, and there is a need to study these children formally rather than to rely on a limited number of questionnaire responses obtained from the parents Paneth Financial costs also need to be considered.
Calculations by the authors of the Radius report indicate that screening four million pregnant women in the USA at dollars per scan would increase costs by one billion dollars per year LeFevre While costs have been shown to be less in other countries Henderson ; Roberts , economic issues will still be relevant, particularly in low-resource settings.
Clinicians, health planners, and pregnant women need to decide if these results justify the expense of providing routine ultrasound examination in early pregnancy. The early Helsinki data may have overestimated the efficiency of scans. Cost savings were assumed on the basis of decreased perinatal mortality which was not borne out in other studies. Maternal anxiety and satisfaction have not been well explored in the studies included in this review. Parents may not be fully informed about the purpose of routine ultrasonography and may be made anxious, or be inappropriately reassured by scans Garcia ; Lalor Ultrasound scans are, however, popular - the potential enjoyment that parents can receive from seeing the image of their baby in utero is discussed elsewhere Neilson The review includes several large trials, although the eligibility criteria of some trials e.
The majority of studies were carried out in high-resource settings where overall levels of perinatal mortality are low and the contribution of major fetal abnormality to mortality is higher than in lower-resource settings. Findings in high-resource settings may not apply in less affluent settings.
Studies were carried out over three decades and technical advances in equipment, more widespread use of ultrasonography in the developed world, and training and expertise of operators are likely to have resulted in more effective sonography, particularly for the detection of fetal abnormalities.
Overall, the review includes several large, well designed trials but the lack of blinding is a problem common to all of the studies and this may have an effect on some outcomes. The possibility of introducing bias was present at every stage of the reviewing process. Serum estriol levels increase with advancing gestation until 40 weeks; there is a progressive decline in estriol values that parallels the decline in amniotic fluid level when the term gestation is exceeded.
Prolonged pregnancy is common in patients with placental sulfatase deficiency. As the placenta ages, increased rates of placental infarction and fibrin deposition decrease placental exchange of wastes and nutrients with the maternal circulation. Placental senescence impairs the transfer of oxygen fuels and the disposition of wastes as the number of villous capillaries and intervillous spaces decline. The postdate fetus experiences a range of physiologic changes that predispose it to the development of hypoxia and acidosis.
These stresses in turn activate the fetal hypothalamic-hypophyseal-adrenal axis to produce more cortisol, attempting to trigger the normal process of uterine activation and stimulation leading to labor. A grade 3 placenta exhibits sonographic findings of linear echogenic densities, probably representing areas of increased calcium deposition, dividing the placental bed into compartments. Echolucent areas may be seen in the central portion of the compartments. The incidence of grade 3 placentas increases after 40 weeks, but its presence alone cannot be used to predict the occurrence of fetal distress or the postmaturity syndrome.
However, Yeh and colleagues 31 found that the postmaturity syndrome was more common when both oligohydramnios and a grade 3 placenta were present. Diminished fetal ventricular function may also hamper the fetus's efforts to maintain renal perfusion.
Eventually, the decrease in amniotic fluid leads to umbilical cord compression. Intermittent cord compression can be diagnosed by identifying the presence of variable decelerations during fetal heart rate testing. Cord compression stimulates the passage of meconium by the same vagal reflex that initiates a heart rate deceleration. Meconium passed into a small amniotic fluid volume tends to be thicker, more tenacious, and more difficult to clear after aspiration. A significant amount of cord compression can lead to hypoxia, acidosis, and fetal distress.
A fetus already compromised by other factors such as diabetes, hypertension, or intrauterine growth retardation has few reserves available to protect it against the additional stresses imposed by the physiologic changes occurring in the postdate pregnancy. They are particularly at risk for increased perinatal mortality. Although placental function decreases in the postdate pregnancy, the total placental area increases so that the exchange of nutrients usually continues to support fetal growth. Therefore, the most common problem associated with postdatism is not postmaturity syndrome, but macrosomia.
The delivery of macrosomic infants is associated with increased rates of labor dystocia, birth trauma, cesarean section, and neonatal complications such as hypoglycemia, temperature instability, and jaundice. Although ultrasound may be helpful in identifying macrosomic infants at risk for birth trauma, clinicians should be aware of the limitations of this modality in predicting birth weight.
The formulas currently used to estimate fetal size are less accurate in macrosomic infants because of variations in head shape and adiposity found in this group.
- persian speed dating.
- free dating services in toronto!
- speed dating in kampala?
- online dating for amputees.
Formulas predicted on estimates of macrosomic populations or which depend less on fetal head size may carry greater accuracy in identifying the fetus at risk for shoulder dystocia. Intrauterine asphyxia results from a deficit in the required amount of oxygen being delivered to the fetus. The deficit results from chronic conditions such as uteroplacental insufficiency or from acute, intermittent cord compression seen in conjunction with oligohydramnios.
Pregnancies complicated by chronic hypertension or diabetes mellitus, already compromised by suboptimal placental function before term, carry a fourfold to fivefold greater risk of perinatal mortality when allowed to continue after the delivery date. Antepartum testing is meant to detect the fetus with hypoxia, but often a dysmature or otherwise compromised fetus exists in a prehypoxic state.
Tests that could consistently identify the prehypoxic fetus at risk for asphyxia would allow this group to be delivered before complications arise. Estriol levels correlate inversely with the rate of fetal heart rate decelerations and the occurrence of fetal distress, 27 but the inconvenience of performing frequent hour urine collections has led to the use of other predictive tests such as the amniotic fluid index.
The reliable identification of a subset of postdate pregnancies at risk for fetal hypoxia and asphyxia obviates routine induction in the low-risk postdate patient. The mechanisms of meconium passage described earlier are more likely to be found in the postdate pregnancy. The meconium also is likely to be thicker and more tenacious because of the frequency of oligohydramnios. Meconium aspiration is eight times more common in postdatism, and its complications include pneumonia, pneumothorax, a requirement for assisted ventilation, and the development of pulmonary hypertension.
Personnel trained in neonatal intubation should be available to intubate and continue suctioning as required. Intrapartum meconium aspiration can be decreased by the use of saline amnioinfusion, which dilutes the meconium and helps to prevent occlusion of the respiratory passages. The pressure catheter continues to provide accurate readings of the intrauterine pressure being generated by contractions.
The hallmarks of the postmature infant as described by Clifford 1 include meconium staining, loss of subcutaneous fat reserves, and skin peeling. The infant's appearance is like that of a wizened old gnome—long, thin, and wrinkled with decreased muscle mass and long nails on the toes and fingers. The decreased stores of fat and glucose predispose these infants to metabolic disturbances such as hypoglycemia, hypothermia, and polycythemia.
Currently, there is no way of predicting in utero which infants will develop the syndrome, although it is more commonly seen after 42 weeks and in conjunction with oligohydramnios. Early reports suggest that the postmature infant experienced quantifiable delays of either mental or physical development that lasted up to the fifth year of life. However, other studies that used rigorous pregnancy dating criteria and stratified infants based on their Clifford staging showed that once the infant passed the perinatal period, its development was comparable with term control infants.
The development of simple, reliable methods for fetal surveillance, the use of ultrasound to determine fetal size and amniotic fluid volume, and the introduction of cervical ripening agents have improved the clinician's ability to manage the postdate pregnancy safely. Before the introduction of adequate methods of fetal surveillance in the s, routine induction of labor at 42 weeks was commonly practiced to improve the perinatal outcome.
Prostaglandin preparations to ripen the cervix are available as a gel dinoprostone [Prepidil] , as a removable sustained-release suppository Cervidil , or as a vaginal tablet misoprostol. These agents sensitize the uterus to the action of uterotonic agents, as well as remodel the cervix, and have encouraged physicians to undertake induction of labor in postdate patients when delivery is indicated.
It should be noted that induced labor roughly doubles the risk for cesarean delivery. The development of simple, inexpensive, and easily interpreted methods of antepartum fetal testing has led to the current practice of watchful waiting in patients with an unfavorable cervix and reassuring antepartum test results, reserving routine induction for patients with an inducible cervix, non-reassuring test results, or other risks for a poor outcome.
Antepartum surveillance generally begins at 41 weeks, or days from the first day of the last menstrual period, because perinatal morbidity and mortality begin to rise before 42 weeks of amenorrhea. The ideal test would be easily administered and easily interpreted, noninvasive, cost-effective, sensitive enough to identify the fetus at risk, and yet specific enough to prevent excessive intervention. Use of the contraction stress test, the nonstress test, or the biophysical profile for antepartum testing decreases the perinatal morbidity and mortality associated with postdatism.
If no late decelerations occur, discontinue stimulation and observe FHR until return to baseline uterine activity. If late decelerations occur, continue stimulation until decelerations can be determined to be persistent or transient. Nonstress testing 50 , 51 , Monitor for reactivity for 20 min; if nonreactive, stimulate fetus with abdominal palpation or glucose administration.
- absolute dating relative dating compare contrast?
- speed dating big ben bern.
- Article information.
Biophysical profile 53 , The contraction stress test remains the gold standard for antepartum fetal surveillance. There were no perinatal deaths using this methodology. Although the low rates of perinatal mortality and morbidity achieved using the contraction stress test attest to its sensitivity, the high percentage of equivocal results obtained can make the test cumbersome to administer to numerous patients. The test also frequently requires the intravenous administration of oxytocin, although sometimes this can be obviated by use of nipple stimulation rather than oxytocin infusion.
The nonstress test now is the most widely used method of antepartum fetal surveillance because of its simplicity and noninvasive nature. Analysis of a fetal heart tracing requires the identification of accelerations, spontaneous decelerations, baseline heart rate, and uterine activity before classifying the tracing as reactive, reactive with decelerations, or nonreactive. Fetal stimulation by palpation or the use of vibroacoustic stimuli can be used to induce reactivity without compromising the validity of the test.
When the nonstress test is performed weekly, perinatal outcome is not as favorable as when the contraction stress test is performed weekly. This is the most widely used form of testing currently. The biophysical profile 53 is unique in its primary reliance on ultrasound parameters rather than fetal heart rate patterns. A normal biophysical profile with all ultrasound parameters identified during the test period of 30 minutes was associated with no perinatal mortality and low rates of perinatal morbidity. An abnormal test requires the use of nonstress testing in addition to ultrasound, with appropriate intervention predicated on the results of the nonstress test.
Doppler velocimetry studies have not been helpful in identifying the postdate infant at risk for intrapartum distress, perhaps because the umbilical arterial and venous diameters are increased in the postdate fetus. Antepartum testing protocols are all designed to signify increased fetal risk. Once the maternal and fetal risks to continuation of the pregnancy are no longer acceptable, the physician will effect delivery. Perinatal fetal morbidity and mortality nadir at 39—40 weeks' gestation.
Several studies have challenged the need to continue with antepartum testing to 42 weeks' gestation, comparing outcomes to a policy of induction once 41 weeks' gestation is achieved. One observational study found that neither policy gave a clear reduction in fetal risks, but did significantly increase the cesarean section rate among nulliparous women undergoing induction at 41 weeks' gestation.
The stillbirth rate declined over this time period, but it is uncertain how much of the benefit is attributable to the shift in delivery timing, as the decline in stillbirth rate was seen at 40, 41 and 42 weeks' gestation. Nulliparous patients undergoing induction can expect an increase in medical interventions and cesarean section rate when interventions begin at 41 weeks' gestation.
Fetal macrosomia occurs at least three times more frequently in postdate pregnancy than in term deliveries. However, the formulas currently available for estimation of fetal size are less accurate in the upper range of the birth weight spectrum because of fetal variation in head shape, adiposity, and muscle mass. Even when this margin remains stable, the absolute value of the difference between estimated and actual weight is greater in larger infants.
Ultrasound identification of a fetus with an estimated weight in excess of g should prompt the physician to consider cesarean delivery, although this remains controversial. Once the timing and route of delivery has been selected, the clinician may be stymied by the presence of an unfavorable cervix.
Most patients with documented postterm pregnancy have a low Bishop score. Membrane stripping by vigorous cervical examination is a widely practiced technique that many practitioners subjectively believe decreases the incidence of postdate pregnancy. A prospective study involving subjects was conducted in which women were randomized to either gentle cervical examination to assess Bishop score or to vigorous membrane stripping. The authors found a statistically decreased frequency of postterm delivery in patients who had undergone membrane stripping. The use of a Foley catheter, relaxin, or breast stimulation also has been advocated for cervical priming.
The use of cervical ripening agents is now the standard of care for patients undergoing induction of labor who present with a Bishop score under 7.