Dizygotic twin pregnancy after transfer of one embryo.

OBJECTIVE: To consider the risk of intercourse without contraception during infertility treatment.
DESIGN: Case report.
SETTING: Leiden University Medical Center. PATIENT(S): An infertile couple underwent IVF for tubal pathology. INTERVENTION(S): Transfer of one embryo during a natural cycle. MAIN OUTCOME MEASURE(S): Human leukocyte antigen typing, histochemical analysis of the fetal membranes, neonatal and maternal clinical outcomes. RESULT(S): A dizygotic twin pregnancy was confirmed after birth by human leukocyte antigen typing of both fetuses and mother and by histochemical analysis of the dividing fetal membranes. This suggests a pregnancy of concurrent IVF and spontaneous conception. Pregnancy was complicated by preeclampsia and intrauterine growth retardation of both fetuses. CONCLUSION(S): We state that couples should abstain from intercourse without contraception during infertility treatment to prevent multiple gestation and its related complications for mother and fetuses.