Spontaneous embryonic loss following in vitro fertilization: incidence and effect on outcomes.

OBJECTIVES: The purpose of this study was to determine the early spontaneous loss rate in multiple pregnancies following assisted reproductive technology (ART). STUDY DESIGN: Analysis of pregnancies following ART as related to the initial number of embryos and maternal age was performed. RESULTS: At least one spontaneous loss was observed in 47.0% (95% CI 29.8-64.9) of quadruplets, 59.3% (95% CI 48.2-69.8) of triplets, and 35.2% (95% CI 29.6-41.2) of twins. The increased loss rates in mothers > or =35 years was related to early twin pregnancies, but not to early triplet and quadruplet gestations. We could not find an effect of the starting number of embryos on either gestational age or birth weight characteristics. CONCLUSION: Our observations did not identify a clear relation between early spontaneous loss of multiple gestations and either initial number of embryos or maternal age. Other factors might be involved in the outcome of ART multiple pregnancies.