Nucleated Red Blood Cells as a Marker of Acute and Chronic Fetal Hypoxia in a Rat Model.

OBJECTIVE: To examine the relationship between duration of fetal hypoxia, nucleated red blood cell (NRBC) count, and fetal growth. METHODS: Pregnant rats were exposed to a severe hypoxia (9.5%-10% O2) for varying time intervals (2, 6, 12, 24, 48, and 120 hours; n=4 for each time interval) immediately prior to delivery at term. Normoxic controls were exposed to room air (21% O2) and matched for all other study variables (n=4 rats for each time interval). Pups were delivered via hysterotomy while maintaining exposure gas concentrations. Blood gas analysis and NRBC counts were performed, and fetal body and liver weights were recorded. Student's t test and simple regression were used for statistical analysis. RESULTS: As the duration of hypoxia increased, fetal weight, liver weight, blood bicarbonate, and base excess levels decreased significantly; concomitantly, NRBC counts increased. This increase in NRBCs became statistically significant after 24 hours of exposure. After 48 hours of hypoxia there was a 2.5-fold rise in NRBC count, and after 120 hours of hypoxia there was a 4.5-fold rise in NRBC count over control levels. After 12 or more hours of hypoxia, fetal body weights were significantly reduced; 120 hours of hypoxia resulted in a 35% reduction in fetal body weight, a 34% reduction in fetal liver weight, and 356% increase in NRBC count. CONCLUSION: In a pregnant rat model, chronic maternal hypoxia (≥24 hours) results in a significant increase in fetal NRBC counts as well as reduced fetal body weight and organ growth.

Combined sonographic and endoscopic umbilical cord occlusion in twin and triplet gestations.

OBJECTIVE: To review our experience with a minimally invasive technique for umbilical cord occlusion as a method of selective feticide in monochorionic sets. STUDY DESIGN: Umbilical cord occlusion was completed using 3 mm bipolar cautery under ultrasound guidance (3D/4D, n = 6; 2D, n = 6) with pre and post ligation endoscopic evaluation. RESULTS: 12 cases of monochorionic sets where selective feticide was performed were identified during the period 2000 to present. There were four triplet and eight twin gestations in the study cohort. Median interval from intervention to delivery was 16 weeks (range, 5-19). All co-twins survived the procedure and 15 of 16 were delivered after 33 weeks. CONCLUSIONS: Umbilical cord occlusion in monochorionic sets can be accomplished in a minimally invasive manner with combined endoscopic and ultrasound guidance in both twin and triplet pregnancies.

Fetal "nonreassuring status" is associated with elevation of nucleated red blood cell counts and interleukin-6.

OBJECTIVE: Previous studies have established the association between fetal hypoxia and elevated nucleated red blood cells (NRBCs). Animal studies have demonstrated that a rise in plasma erythropoietin (EPO) is not detectable until 4 to 6 hours after the initiation of hypoxia. In contrast, interleukin-6 (IL-6) has the capacity to directly induce erythroid maturation. Therefore, we set forth to evaluate the role of EPO and IL-6 as potential mediators of elevated fetal NRBCs in response to acute hypoxia. STUDY DESIGN: Low-risk pregnancies with a normal fetal heart rate at admission to labor and delivery were eligible for participation. Deliveries for "nonreassuring fetal status" comprised the study group. All other deliveries served as controls. Umbilical cord blood was prospectively collected for blood gas analysis, NRBC counts, EPO, and IL-6. RESULTS: One hundred women participated in the study. Nonparametric univariate analysis demonstrated a significant association between elevated NRBC counts and Apgar scores, arterial cord blood pH, base excess, EPO, and IL-6 levels (all P values <.01). Stepwise regression analysis identified only pH, IL-6, and EPO as independent variables associated with elevated NRBC counts at birth (all P values <.0001 with R2 of 0.27, 0.42, and 0.46, respectively). A significant increase in NRBC counts was noted in study patients. IL-6 was significantly increased in study patients, whereas there was no difference in EPO between groups. CONCLUSION: The fact that NRBC counts were elevated in fetuses who were delivered for "nonreassuring fetal status" with EPO being normal and IL-6 being elevated implies that IL-6 may have a unique, short-term role in elevating fetal NRBC counts.

Are elevated fetal nucleated red blood cell counts an indirect reflection of enhanced erythropoietin activity?

OBJECTIVE: Animal and human studies demonstrated elevated erythropoietin (EPO) levels in response to intrauterine hypoxic events. Other studies documented an association between fetal hypoxia and elevated nucleated red blood cell (NRBC) counts and have speculated that it is the elevation of EPO that results in an increase in NRBC counts. Thus, the purpose of our study was to determine the correlation between EPO levels and NRBC counts in the human fetus. STUDY DESIGN: Data were collected prospectively between April and July of 2003. Term singleton pregnancies were eligible to participate in the study. Umbilical cord blood was collected immediately after birth for determination of fetal EPO levels and NRBC counts. RESULTS: Forty pregnancies formed the study population. The mean gestational age at delivery was 39.5 +/- 1.2 weeks (+/-SD) and the mean birth weight was 3500 +/- 372 g. The median EPO (mU/mL) was 34 (range 13-427). The median NRBC/100 white blood cells was 10 (range 0-150). A simple regression analysis indicated that NRBC counts are significantly and positively correlated with EPO (P=.0004, R(2)=0.287). CONCLUSION: Our results suggest a significant association between EPO and NRBC counts in term singleton fetuses. These results support the hypothesis that fetal NRBC and EPO are interrelated. However, the relatively low R(2) indicates that there are other (yet to be determined) hypoxia-derived mediators that result in an elevation of fetal NRBC counts.

Congenital laryngeal atresia associated with partial diaphragmatic obliteration.

OBJECTIVE: Laryngeal atresia is a rare, life-threatening congenital malformation. Prenatal sonographic diagnosis has been described; however, in many cases, the precise diagnosis is established only at autopsy. Our aim was to describe an atypical prenatal presentation of congenital laryngeal atresia in which the final diagnosis was made only at autopsy. METHODS: Sonographic and postmortem examinations were performed on a fetus with bilateral enlarged echogenic lung fields, an everted diaphragm, and polyhydramnios, which were initially noted on prenatal sonography at 26 weeks' gestation. RESULTS: Unfortunately, the mother was lost to follow up at our inner-city clinic, thus precluding a definitive diagnosis. At birth, tracheostomy was not performed because of the anomalous appearance of the neonate and the suspicion of multiple congenital anomalies. Neonatal death occurred after 18 minutes of life. Autopsy revealed laryngeal atresia with a right hemidiaphragmatic defect and multiple other congenital anomalies. CONCLUSIONS: This was a rare case with prenatal sonographic findings in a fetus with congenital laryngeal atresia associated with partial diaphragmatic obliteration.