Abstract 273 Poster Session I, Saturday, 5/1 (poster 142)

Introduction: Regulation of vascular tone in fetal placental circulation is not under control, leaving myogenic mechanisms and locally produced autacoids (Prostacyclin and Nitric Oxide {NO}) as the main contributors to the low resistance of the fetal systemic circulation. In addition, many endogenous substances potentially capable of affecting fetal vascular resistance and blood flow have been found in umbilical blood. However, nitric oxide's role in regulating the tone of the feto-placental circulation and in neonatal adaptation is not fully understood.

Objective: As part of a broad, comprehensive study, the aim of this particular investigation is to compare the levels of nitroc oxide in venous and arterial cord blood of healthy term infants.

Methods: Cord venous and arterial blood was collected immediately after cord clamping, centrifuged at 2500 rpm for 10 min., frozen at -80°, and stored for 30-60 days. Nitric Oxide levels were measured using the Sievers 280 NO Analyzer (Boulder, CO) using vanadium (III) chloride to reduce serum nitrate/nitrite to nitric oxide and subsequent measurement by chemiluminescence. The results were analyzed using Student t-test: p<0.05.

Results: To date, we have studied 22 term infants with uncomplicated pregnancies and deliveries (Apgar 8.3 and 9.0 at 1 and 5 min. respectively) Twelve infants were delivered by normal spontaneous vaginal delivery (NSVD), 6 infants were delivered by elective C-section without preceding labor, and 4 by C-section after labor. All infants had uncomplicated neonatal courses. (Table)

Table 1 No caption available
Full size table

Conclusion: These preliminary results show that, immediately after cord clamping, cord arterial nitric oxide is not significantly different from vein nitric oxide in healthy term pregnancies, regardless of mode of delivery. We speculate that, during normal immediate transition from fetal to neonatal life, cord vein and artery endothelium produce nitric oxide at a similar rate.