Third-trimester prediction of small-for-gestational-age infants in pregnant women with sickle cell disease. Development of the ultradop index.

Twenty-seven women with homozygous sickle cell disease were followed from the third trimester until delivery. All the subjects underwent both Doppler and sonographic assessment at two points in pregnancy, periods I (28-30 weeks) and II (34-36 weeks). Estimated fetal weight (EFW) was calculated. Using a continuous wave Doppler instrument, mean systolic:end diastolic (S:D) ratios were calculated to characterize the umbilical waveforms. S:D ratios greater than or equal to 3 were designated abnormal. An index, the ultra-dop, was developed that combined ultrasound EFW less than or equal to 25th percentile and S:D greater than or equal to 3. Nine of 27 infants (33%) were small for their gestational age, with a mean gestational age of 38 +/- 2 weeks. The sensitivity, specificity and predictive values were calculated for smallness for gestational age utilizing ultrasound, Doppler velocimetry and the ultradop index for periods I and II. For period I, the highest sensitivity was obtained with the ultradop index--88.9% as compared to 77.8% with Doppler scanning and 11.1% with ultrasound. The ultradop also provided the highest positive predictive value, 88.9%; it was followed by Doppler at 77.8% and ultrasound at 50.0%. In period II the ultradop index and Doppler had the same sensitivity, 88.9%, which was much higher than for ultrasound (55.6%). As for period I, the ultradop had the highest positive predictive value, 88.9%. Our data suggest that the ultradop index provides a key assessment of women with sickle cell disease at 28-30 weeks' gestation with reference to the likelihood of their giving birth to small-for-gestational-age infants.