INTERFETAL HEART-RATE AND SIZE VARIATION IN FIRST-TRIMESTER MULTIFETAL PREGNANCIES AND HEART-RATE OF SURVIVING FETUSES AFTER FETAL REDUCTION

The objective of this study was to determine the variation in first-tr imester fetal size and fetal heart rates in multifetal pregnancies, an d to study the effect of fetal reduction on the surviving fetal heart rate. Fetal crown-rump length and fetal heart rates were measured in 4 4 patients with multifetal pregnancies who underwent fetal reduction. The heart rates of the surviving fetuses were also measured immediatel y after, and 1 h following the procedure. A total of 143 fetuses were evaluated prior to reduction and 75 fetuses following the procedure. T here was no significant difference in crown-rump length between fetuse s of the same gestation. The interfetal fetal heart rate variation bet ween fetuses of the same gestation, expressed as a standard deviation, was 4.78 +/- 0.51 beats/min (mean standard deviation +/- standard err or of the mean) before reduction; this was a significantly greater var iation than could be attributed to error in the measurement of heart r ate. In the surviving fetuses, the mean heart rate did not change. How ever, immediately after the reduction, interfetal heart rate variation was abolished, but was observed again 1 h after the reduction. We con clude that in first-trimester multifetal pregnancies (1) there is no s ignificant difference in fetal crown-rump length; (2) there is interfe tal variation in heart rates; and (3) fetal reduction has only a limit ed effect on the heart rates of surviving fetuses.