Ultrasonographic growth measurements in triplet pregnancies

The incidence of triplet pregnancies is increasing due to the widespread use of ovulation induction agents and assisted conception treatments. The aim of this study was to acertain the normal ultrasonographic measurements for fetal growth parameters in triplet pregnancies. The ultrasonographic measurements of all triplet pregnancies managed in two major hospital centres were reviewed retrospectively and those in which there was less than 25% discordance in birth weight were included in the study. Triplet 50th centile for fetal biparietal diameter, whilst falling through the normal singleton centile range from 27 weeks gestation, did not fall below the 10th centile value of singletons. Triplet 50th centile for head circumference was equivalent to the singleton 10th centile from 23 weeks gestation. Triplet 50th centile for abdominal curcumference was persistently below that of the singleton 50th centile, falling below the singleton 10th centile from 29 weeks gestation. Normal growth rate of triplet gestations in the third trimester of pregnancy varies from that of singletons. An awareness of this altered growth rate is necessary to avoid the inappropriate diagnosis of asymmetrical triplet fetal growth retardation. We suggest that the growth curves presented here may be used to monitor triplet fetal growth.