Normogram of umbilical artery Doppler indices in singleton pregnancies in south-western Nigerian women.

AIM: To determine the Doppler indices of the umbilical arteries in normal singleton pregnancy with a view to generating local reference ranges.

METHODS

In this prospective, cross-sectional study, 400 pregnant women at 15-39 weeks' gestational age, with estimated fetal weight within the 10th and 90th percentile, no fetal malformation(s), and without any history of maternal medical disease, were recruited. Umbilical arteries were assessed on ultrasound, with the subjects in the supine position. Resistivity index (RI), pulsatility index (PI) and systolic/diastolic (S/D) ratio were recorded and analyzed.

RESULTS

All the umbilical arteries were paired; no single umbilical artery was seen. Mean RI, PI, and S/D ratio declined with gestational age, and decreased from 1.265 to 0.829, from 0.760 to 0.585 and from 4.068 to 2.365, respectively, from 15 to 39 weeks of gestation. With regard to correlation between gestational age and Doppler indices, r = - 0.598 for PI (P < 0.05), - 0.437 for RI (P < 0.05), and - 0.538 for S/D ratio (P < 0.05). Decline in the Doppler indices was progressive with gestational age.

CONCLUSION

A normogram of umbilical artery Doppler indices was constructed, which showed that the indices decreased with gestational age. These normative data could serve as reference ranges for evaluation of the umbilical artery circulation in this locality.