Accuracy of ultrasound estimation of fetal weight in multiple pregnancies

Our objective was to assess the accuracy of ultrasonographic estimation of fetal weight in twins and triplets as compared to singleton pregnancies. Retrospective analysis was undertaken of ultrasound data of all fetuses who underwent an examination within 1 week of delivery (singletons 1832, twins 518, triplets 51). At birth weights below 2500 g, there was a significant overestimation of fetal weight in twins as compared to singletons, but the accuracy of the estimate was the same, except in twins between 1500 and 2499 g, when the weight was based on abdominal circumference and femur length alone. At birth weights of more than 2500 g, no difference was detected between twins and singletons. At all birth weights below 2500 g, the accuracy of weight estimation in triplets was equal to that in singletons and there were no triplets above this weight. We conclude that ultrasonographic estimation of fetal weight is as accurate in twins and triplets as it is in singletons.