Interfetal heart rate and size variation in first-trimester multifetal pregnancies and heart rate of surviving fetuses after fetal reduction

Abstract

The objective of this study was to determine the variation in first-trimester fetal size and fetal heart rates in multifetal pregnancies, and to study the effect of fetal reduction on the surviving fetal heart rate. Fetal crown-rump length and fetal heart rates were measured in 44 patients with multifetal pregnancies who underwent fetal reduction. The heart rates of the surviving fetuses were also measured immediately after, and 1 h following the procedure. A total of 143 fetuses were evaluated prior to reduction and 75 fetuses following the procedure. There was no significant difference in crown-rump length between fetuses of the same gestation. The interfetal fetal heart rate variation between fetuses of the same gestation, expressed as a standard deviation, was 4.78 ± 0.51 bents/min (mean standard deviation ± standard error of the mean) before reduction; this was a significantly greater variation than could be attributed to error in the measurement of heart rate. In the surviving fetuses, the mean heart rate did not change. However, immediately after the reduction, interfetal heart rate variation was abolished, but was observed again 1 h after the reduction. We conclude that in first-trimester multifetal pregnancies (1) there is no significant difference in fetal crown-rump length; (2) there is interfetal variation in heart rates; and (3) fetal reduction has only a limited effect on the heart rates of surviving fetuses.