Routine third trimester ultrasonography in predicting adverse perinatal outcomes: a prospective cohort study at a...

Fetal growth restriction (FGR) may go undetected in the antenatal period with subjective clinical evaluation, and there is a growing propensity to perform a third-trimester scan, especially in the developed countries. The literature on the importance of the same in developing countries like ours, is scant. Hence, this study was undertaken to evaluate the role of routine third-trimester ultrasonography along with Doppler in predicting adverse perinatal outcome.

A prospective cohort study was conducted at a tertiary-care hospital, in which routine third-trimester ultrasonography was performed for 265 antenatal women, and included estimation of amniotic fluid index (AFI), estimated fetal-weight (EFW), and cerebroplacental ratio (CPR). Women were categorized as having normal parameters or having at least one abnormal parameter. Post-natal adverse perinatal outcomes including low birth-weight, hypoglycemia, poor Apgar scores, prolonged hospital stay, need for ventilatory support, neonatal asphyxia, neonatal sepsis and early neonatal death were recorded. Prediction analyses for sensitivity, specificity, positive and negative predictive values were done. Receiver Operating Characteristic (ROC) curves were plotted for threshold for each parameter for adverse outcome.

Out of 260 women that were analyzed, 47.5% had no clinically identifiable risk factors, and 52.5% had at least one abnormal parameter. Sensitivity and negative predictive value for adverse outcome were highest for composite ultrasound finding (85.4% and 90.4% respectively). Specificity, positive predictive value and diagnostic accuracy were highest for CPR (97.8%, 86.7% and 76.9% respectively).

Routine third trimester ultrasonography, including Doppler, can help in risk-stratification of otherwise clinically low-risk pregnancies.