Postterm Group Research Articles

A longitudinal study of maternal dose response to low molecular weight heparin in pregnancy.

To assess the maternal response to low molecular weight heparin during pregnancy, by estimation of plasma anti-Xa activity, at three specified gestation points and in the nonpregnant state. A longitudinal, prospective, observational study was set in a tertiary referral recurrent miscarriage clinic. Twenty-four women, attending consecutively, were invited to participate and gave informed consent. Each woman had a history of recurring pregnancy loss and positive preconception screening for antiphospholipid syndrome. After confirmation of a viable pregnancy all subjects began taking 5000 IU of dalteparin once daily subcutaneously. Serial measurement of plasma anti-Xa activity after administration of dalteparin was performed at three standard gestation points (12, 24, and 36 weeks) and in the nonpregnant state (6 weeks postpartum). Peak anti-Xa levels occurred at 4 hours postbolus in pregnancy, as compared with 2 hours in the nonpregnant state. The mean anti-Xa levels at 12, 24, and 36 weeks' gestation were significantly reduced, at 2 hours postinjection, as compared with the nonpregnant state (P <.001, P <.01, P <.001, respectively). The lowest dose-response curve was at 36 weeks' gestation. A repeated-measures analysis of variance found a significant difference (P <.05) between the 36-week group and the postterm group but not between any of the other groups. During pregnancy, differences in the pharmacokinetics of low molecular weight heparin were observed, with an overall reduction in anti-Xa activity. On the basis of this study it is questionable to extrapolate dosing and lack of dose monitoring, in pregnant women, using data derived from a nonpregnant population.

Pre-term cervical ripening and labor induction

Objective: To evaluate retrospectively pre-term induction; with Prostaglandin (PG) E 2-gel and i.v. oxtytocin, respectively. Methods: Fifty pre-term women with a gestational age between 28+0 and 36+6 and medical indications for labor induction were compared with the two next induced at term and post-term. The obstetric end points were numbers of PGE 2-gel applications, failed inductions, instrumental delivery and heavy bleeding after partus (>1000 ml). The neonatal outcome was registered as operative delivery for fetal distress (ODFD) or Apgar score <7 at 5′. Results: The number of PGE 2-gel applications did not differ. The duration of labor was shorter in the pre-term group ( P=0.043). A five-fold higher risk of heavy postpartum bleeding (>1000 ml) was noticed in the post-term group compared to the pre-term. The incidence of low Apgar scores were similar in the three groups. Conclusions: Safe vaginal labor induction and delivery can be anticipated pre-term with PGE 2-gel.

Elevated Mid-Trimester Maternal Corticotrophin-Releasing Hormone Levels in Pregnancies That Delivered Before 34 Weeks

The most effective interventions for optimizing the neonatal outcome in preterm births are tocolysis and antenatal glucocorticoid treatments, but their value is limited when women present with advanced cervical dilatation. Recent evidence suggesting a rapid rise in maternal corticotropin-releasing hormone (CRH) prompted this study, which was aimed at learning whether midtrimester levels are significantly elevated in a Chinese population when women deliver before 34 weeks’ gestation. Venous blood levels of CRH were estimated by radioimmunoassay in 1014 low-risk women enrolled at 15 to 20 weeks’ gestation. Assay results were obtained by investigators who had no knowledge of the obstetrical outcome. The parturients, whose average age was 31 years, were at 18 weeks’ gestation on average when sampled. Sixty-four women, 6.3 percent of the series, delivered preterm. Forty delivered spontaneously, whereas 24 had labor induced for obstetrical reasons. Plasma CRH levels increased with advancing gestation. When corrected for gestational age and expressed as multiples of the median (MoM) for normal term pregnancies at the same gestational age, values were 1.32 MoM for spontaneously preterm births, 1.07 for iatrogenic preterm births, 1.00 for term deliveries, and 0.7 for postterm deliveries. The spontaneous preterm group had significantly higher levels than the postterm group. The best cutoff for predicting delivery before 34 weeks was 1.9 MoM. Its sensitivity and specificity were 73 and 78 percent, respectively, and its positive and negative predictive values were 4 and nearly 100 percent, respectively. The relative risk of delivering before 34 weeks with a cutoff of 1.9 MoM was 9.4. These findings are consistent with reports on mainly white study populations and support the idea that some placental process taking place as early as midtrimester influences the length of gestation. Plasma CRH, however, had low predictive power in this low-risk group. Br J Obstet Gynaecol 1999;106:1041–1046

Fetal outcome in pregnancies defined as post-term according to the last menstrual period estimate, but not according to the ultrasound estimate.

To study the risk of adverse fetal outcome in fetuses that were post-term according to the last menstrual period estimate but not according to the ultrasound estimate. A total of 11,510 women with singleton pregnancies, reliable last menstrual period and delivery after 37 weeks were divided into four groups: women who delivered at term, i.e. within 259-295 days according to both the ultrasound and the last menstrual period estimate; women who delivered post-term according to the last menstrual period estimate but not according to the ultrasound estimate; women who delivered post-term according to the ultrasound estimate but not according to the last menstrual period estimate; and women who delivered post-term according to both the ultrasound and the last menstrual period estimates. Stepwise logistic regression was used to test whether the risk of Apgar score of < 7 after 5 min and transfer to the neonatal intensive care unit increased in any of the post-term groups. There was no significant difference in mortality between the term group and the three study groups. There was no significant increase in the risk for Apgar score of < 7 after 5 min or transfer to the neonatal intensive care unit for pregnancies that were defined as post-term according to the last menstrual period estimate but not according to the ultrasound estimate. There was, however, an increased risk for Apgar score of < 7 after 5 min in the group that was post-term according to the ultrasound estimate but not according to the last menstrual period estimate. There was also an increased risk for transfer to the neonatal intensive care unit in the group that was post-term according to both estimates. The effect of ultrasound in changing the estimated day of delivery to a later date leading to pregnancies becoming post-term according to the last menstrual period estimate but not according to the ultrasound estimate does not have any adverse consequences for the fetal outcome. However, there seems to be an increased risk for adverse consequences for pregnancies that are post-term according to the ultrasound estimate.

Comparison of outcomes in uncomplicated term and post-term pregnancy following spontaneous labor.

This study was designed to compare outcomes of spontaneous labor in uncomplicated term and post-term pregnancy. It comprised of a case matched study of 285 women with uncomplicated singleton post-term pregnancy (290-301 days of gestation) and 855 women with uncomplicated singleton term pregnancy (259-287 days of gestation). Term controls were matched to post-term cases on a 3:1 basis. The main outcome measures were cesarian section, Apgar scores and admission to the Neonatal intensive care unit (NICU). Cesarian section was significantly more common in women with post-term pregnancy (Relative Risk = 1.90, 95% CI = 1.29-2.85). The increase was equally distributed between cesarian sections performed for failure to progress in labor (RR = 1.74, 95% CI = 1.02-3.04) and fetal distress (RR = 2.00, 95% CI = 1.14-3.61). There were no differences in low Apgar scores, but admission to the NICU was more common in the post-term group (RR = 2.69, 95% CI = 1.39-5.54). There was no difference in significant neonatal pathology in either group. Uncomplicated post-term pregnancy is associated with increased rates of obstetric and neonatal interventions in terms of cesarian section and NICU admissions. This effect does not appear to be a result of underlying pathology associated with post-term pregnancy. We suggest that a lower threshold for clinical intervention in pregnancies perceived to be "at-risk" may be a significant contributing factor.

Fetoplacental steroid metabolism in prolonged pregnancies

The response to an intravenous load of 50 mg of dehydroepiandrosterone sulfate given to women with a pregnancy prolonged to more than 42 weeks was compared to the response in control pregnant women at 40 weeks. The half-life of dehydroepiandrosterone sulfate was longer in the prolonged pregnancy group than in the control group (mean ± SEM, 3.64 ± 0.24 hour versus 2.78 ± 1.08 hour, p < 0.05), and the rises of serum free estrone and free estradiol 4 hours after infusion were less in the prolonged pregnancy group than in the control group. Maternal venous and umbilical venous estrone, estradiol, free estriol, and dehydroepiandrosterone sulfate levels were compared in samples from control, postmature, and postterm groups. Umbilical estriol concentrations were significantly less in the postmature group (67.8 ± 9.5 ng/ml, mean ± SEM) than in the control group (136 ± 22.8 ng/ml, mean ± SEM, p < 0.01), but there were no significant differences between dehydroepiandrosterone sulfate, estrone, and estradiol levels. Maternal venous estriol levels were lower in the postmature group (13.3 ± 2.1, p < 0.05) than in the control group (25.0 ± 4.9). A reduction in overall placental estrogen production was indicated by the results of the dehydroepiandrosterone sulfate loads in the patients with prolonged pregnancy, yet the normal umbilical venous estrone and estradiol levels do not fit this conclusion. There is no explanation for the discrepancy at this time.

Morphological observations of the fetal rat spleen during prolonged gestation.

The ultrastructure of splenic cells and frequency of cell types were examined in fetal rats during progesterone-induced (P23, 24, 25) and surgically-induced (S23, 24, 25) prolonged gestation, and compared to term (T) fetuses and newborn animals (N1, N2, N3). Statistical analysis revealed an increase in numbers of erythroblasts and a decrease in numbers of neutrophils in post-term fetuses distinct from that seen in term and newborn animals. However, there were also significant differences between the post-term groups: the frequency of erythrocytes and total number of cells were higher in the drug-treated group, despite similar splenic weights in the two. The results are interpreted as a response by the spleen (increased erythropoiesis) to fetal hypoxia, which is known to exist during prolonged gestation.

Uterine contractility and oxytocin sensitivity in preterm, term, and postterm pregnancy

The records of 117 patients who had serial nonstress tests (N = 285) and oxytocin challenge tests (N = 268) were analyzed to determine whether baseline uterine contractility and/or oxytocin sensitivity changed with increasing gestational age. The results obtained in patients who were delivered before, at, and after term were compared. Uterine contractility and oxytocin sensitivity increased in all groups as gestational age progressed. No significant differences in uterine contractility were noted among groups; however, oxytocin sensitivity was significantly increased in the preterm group (p < 0.001) and decreased in the postterm group (p < 0.001). Our results suggest that the response of the uterus to oxytocin early in pregnancy may help to identify patients who will be delivered before or after term.

Transplacental hemorrhage in postterm pregnancies

The sizable transplacental hemorrhage correlates with risk of isoimmunization in the Rh system. Knowledge whether postterm pregnancies carry higher risk of isoimmunization is important in management of the “unsensitized” pregnancy in rhesus-negative mothers. The combined prospective and retrospective study of 340 pregnancies at The Johns Hopkins Hospital used the Kleihauer method to single out the sizable transplacental hemorrhages before and after term. No difference in number of sizable transplacental hemorrhages is found between the preterm and postterm groups. The authors feel that routine induction of labor at term or even up to 2 weeks post term is not justified in Rh-unsensitized patients on the basis of increased risk of rhesus isoimmunization.

Fetal hemoglobin as an index of maturity

The percentage of fetal hemoglobin was determined in 200 samples of cord blood and an attempt was made to correlate this percentage with fetal age and weight. In the term group fetal hemoglobin varied from 55 to 95 per cent with an average of 73.3 per cent. The preterm group averaged 80.6 per cent with a range of 66 to 92 per cent, while the postterm group had an average of 67.6 per cent with a range of 42 to 80 per cent.The average per cent of fetal hemoglobin in infants weighing between 2,500 grams and 4,000 grams was 74.1 per cent. Those infants below 2,500 grams had an average of 84.6 per cent and those over 4,000 grams had an average of 66.2 per cent.