Amniotic fluid and umbilical cord serum erythropoietin in term and prolonged pregnancies

OBJECTIVE

Erythropoietin - a hormone regulating erythropoiesis - is a biomarker of chronic fetal hypoxia. High erythropoietin levels in fetal plasma and amniotic fluid are associated with increased risk of adverse neonatal outcome. Since the risk of perinatal morbidity and mortality is increased in pregnancies beyond 41 gestational weeks, we evaluated erythropoietin levels in amniotic fluid and umbilical cord serum in apparently low-risk term (≥ 37 gestational weeks) and prolonged pregnancies (≥ 41 gestational weeks) with labor induction.

STUDY DESIGN

This prospective cohort study comprised 93 singleton pregnancies at 37⁺⁰-42⁺¹ gestational weeks, of which prolonged pregnancies numbered 63 (67.7%). Amniotic fluid samples were collected at time of labor induction by amniotomy. Umbilical cord blood samples for evaluation of pH, base excess, and umbilical cord serum erythropoietin were collected at birth. Erythropoietin levels were measured by immunochemiluminometric assay. Normal value of amniotic fluid erythropoietin level was defined as ≤ 3 IU/L, and abnormal value as ≥ 27 IU/L. Normal umbilical cord serum erythropoietin was defined as < 40 IU/L. Data on maternal pregnancy and delivery characteristics and short-term neonatal outcomes such as Apgar score were obtained from the hospital charts. Associations were calculated using Spearman's rank correlation coefficient. The Chi-square test, Fisher's exact test and the Mann-Whitney U test were utilized to determine differences in the study groups.

RESULTS

Amniotic fluid erythropoietin levels correlated with gestational age (r = 0.261, p = 0.012) and were higher among prolonged pregnancies as compared to term pregnancies (p = 0.005). There were 78 (83.9%) vaginal deliveries, and among these erythropoietin levels in amniotic fluid correlated with the levels in umbilical cord serum (r = 0.513, p < 0.000). Umbilical cord serum erythropoietin levels correlated with gestational age among vaginal deliveries (r = 0.250, p = 0.027). Erythropoietin levels in amniotic fluid and umbilical cord serum did not correlate with umbilical artery pH or base excess, or other adverse pregnancy outcome.

CONCLUSIONS

In vaginal deliveries erythropoietin levels in amniotic fluid correlated with the levels in umbilical cord serum. Erythropoietin levels correlated with gestational age, probably due to weakening placental function and relative hypoxemia occurring in advanced gestation. However, in this relatively low-risk study population erythropoietin was not related to adverse delivery outcome.

Fetal cerebral and cardiac hemodynamics in postdate pregnancy

Objective: We aimed to determine the fetal cerebro-placental Doppler indices and modified myocardial performance index (Mod-myocardial performance index (MPI)) in this homogenous group of postdated pregnancies. Methods: A total of 92 singleton pregnant women were included in this prospective study. The study involved three groups; full term control (Group 1, n = 42, 39 0/7 to 40 6/7 week' gestation), late term (Group 2, n = 34, 41 0/7 to 41 6/7 week' gestation) and post term (Group 3, n = 16, ≥ 42 0/7 weeks' gestation). Each participant underwent a Doppler assessment of the fetal umbilical artery (UA), middle cerebral artery (MCA), Mod-MPI. We determined the correlation of the Doppler indices and mod-MPI in patients with unfavorable outcome. Results: MCA pulcatility indices (PI), cerebroplacental ratio (CPR) values were significantly higher in the control group than those in the late-term and post-term groups (Group 1: 1.63 ± 0.3, Group 2: 1.27 ± 0.51, Group 3: 1.13 ± 0.22, respectively, p < .001). The Mod-MPI was significantly higher in the late-term and post-term groups than in the control group (Group 1:0.38 ± 0.1, Group 2: 0.59 ± 0.09, Group 3: 0.60 ± 0.08, respectively, p < .001. MCA PI and CPR were only significantly lower in patients with unfavorable outcome). The threshold value for CPR levels for predicting unfavorable outcome in postdate pregnancies was calculated as 1.11 (area under curve [AUC] 0.762, confidence interval [CI] 0.575-0.95) with 72.7% sensitivity and 71.8% specificity. Conclusions: Fetal Mod-MPI does not differ in postdate pregnancies with favorable and unfavorable outcome. The monitorization of fetal well-being with CPR may help to clinicians to select patient for expectant management in postdate pregnancies.

A mouse model of antepartum stillbirth

BACKGROUND

Many stillbirths of normally formed fetuses in the third trimester could be prevented via delivery if reliable means to anticipate this outcome existed. However, because the etiology of these stillbirths is often unexplained and although the underlying mechanism is presumed to be hypoxia from placental insufficiency, the placentas often appear normal on histopathological examination. Gestational age is a risk factor for antepartum stillbirth, with a rapid rise in stillbirth rates after 40 weeks' gestation. We speculate that a common mechanism may explain antepartum stillbirth in both the late-term and postterm periods. Mice also show increasing rates of stillbirth when pregnancy is artificially prolonged. The model therefore affords an opportunity to characterize events that precede stillbirth.

OBJECTIVE

The objective of the study was to prolong gestation in mice and monitor fetal and placental growth and cardiovascular changes.

STUDY DESIGN

From embryonic day 15.5 to embryonic day 18.5, pregnant CD-1 mice received daily progesterone injections to prolong pregnancy by an additional 24 hour period (to embryonic day 19.5). To characterize fetal and placental development, experimental assays were performed throughout late gestation (embryonic day 15.5 to embryonic day 19.5), including postnatal day 1 pups as controls. In addition to collecting fetal and placental weights, we monitored fetal blood flow using Doppler ultrasound and examined the fetoplacental arterial vascular geometry using microcomputed tomography. Evidence of hypoxic organ injury in the fetus was assessed using magnetic resonance imaging and pimonidazole immunohistochemistry.

RESULTS

At embryonic day 19.5, mean fetal weights were reduced by 14% compared with control postnatal day 1 pups. Ultrasound biomicroscopy showed that fetal heart rate and umbilical artery flow continued to increase at embryonic day 19.5. Despite this, the embryonic day 19.5 fetuses had significant pimonidazole staining in both brain and liver tissue, indicating fetal hypoxia. Placental weights at embryonic day 19.5 were 21% lower than at term (embryonic day 18.5). Microcomputed tomography showed no change in quantitative morphology of the fetoplacental arterial vasculature between embryonic day 18.5 and embryonic day 19.5.

CONCLUSION

Prolongation of pregnancy renders the murine fetus vulnerable to significant growth restriction and hypoxia because of differential loss of placental mass rather than any compromise in fetoplacental blood flow. Our data are consistent with a hypoxic mechanism of antepartum fetal death in human term and postterm pregnancy and validates the inability of umbilical artery Doppler to safely monitor such fetuses. New tests of placental function are needed to identify the late-term fetus at risk of hypoxia to intervene by delivery to avoid antepartum stillbirth.