Serial third trimester ultrasound examinations in predicting fetal weight

Objective: The aim of this study was to compare the accuracyof estimated fetal weights obtained by ultrasonographiesperformed at different weeks in the third trimesterand just before delivery.Methods: A total of 664 patients underwent three serialultrasonographic examinations in the third trimester. Thesonographically estimated fetal weight was calculated usingthe Hadlock formula and then converted into percentiles.The estimated fetal weight percentiles were comparedwith the actual birth weight percentiles at delivery.Results: Mean maternal age was 30±4 years (18-42years), mean gestational age at first ultrasound was32±0.5 weeks (30.4-33.6 weeks), mean gestational ageat second ultrasound was 36±0.4 weeks (35-36.9 weeks),mean gestational age at third ultrasound was 38.6±1weeks (36.3– 42 weeks). Mean gestational age at deliverywas 39± 1 weeks (36-42 weeks), mean birth weightwas 3422±423 grams (1900-4900 grams). Correlationcoefficients of estimated fetal weights percentiles at first,second and third ultrasounds were significantly correlatedwith birth weight percentiles (r=0.556, p<0.001), (r=0.623,p<0.001), (r=0.747, p<0.001, respectively).Conclusion: Ultrasonographic fetal weight estimationscorrelate with the actual birth weight better when performedin the late third trimester, but ultrasonographic fetalweight estimation early in the third trimester may allowfor better follow up and planning of delivery both in smalland large for gestational age fetuses. J Clin Exp Invest2013; 4 (1): 28-33Key words: Fetal weight estimation, third trimester ultrasound,Hadlock formula