Multiple gestations from in vitro fertilization: successful implantation alone is not associated with subsequent preeclampsia.

Objective: Our purpose was to compare the risk for preeclampsia and severe preeclampsia in triplet and twin gestations and to evaluate the effect of successful implantation on the development of preeclampsia and on perinatal outcome in triplet pregnancies conceived by means of in vitro fertilization.
Study Design: A case control study was conducted of triplet pregnancies (n = 38) matched for maternal age, parity, race, and delivery date with twin pregnancies (n = 38) resulting from a single fetal reduction (spontaneously or by means of multifetal pregnancy reduction) after successful implantation of triplets. All pregnancies were conceived by means of in vitro fertilization. Rates of preeclampsia and other maternal complications, factors affecting implantation, and perinatal outcomes were compared. Preeclampsia and severe preeclampsia were defined by The American College of Obstetricians and Gynecologists criteria. The Student t test and the chi(2) test were used for statistical analysis.
Results: The triplet group had a higher rate of severe preeclampsia (26.3%) than the twin (reduced triplet) group (7.9%). The prevalence of preeclampsia (mild and severe combined) also was higher among the triplet group (44.7%) than among the twin group (15.8%). There was no difference in other maternal complications of pregnancy or in factors potentially affecting implantation, such as assisted hatching. Mean fetal weight was lower among the triplet group, but gestational age at delivery was not significantly different.
Conclusions: The rate of preeclampsia is higher among triplets conceived by means of in vitro fertilization than among triplets conceived by means of in vitro fertilization and reduced to twins. This finding suggests that fetal number, placental mass, or factors unrelated to the success of implantation are more important to the development of preeclampsia than is successful implantation alone.