Molar pregnancy with a coexistent fetus after intracytoplasmic sperm injection. A case report.

Normal fertilization is usually considered to have occurred when two pronculei (2PN) and two polar bodies are observed. Exceptions are the single pronucleated zygote resulting from asynchronous pronuclei.A 29-year-old woman entered a program of intracytoplasmic sperm injection and embryo transfer because of her husband's oligoasthenoteratozoospermia. Two cleavage-stage embryos (four blastomeres, grade 1 and 2) were obtained from one fertilized oocyte containing distinct 2PN and the other a single pronucleus (1PN). At 15 weeks' gestation the patient developed severe preeclampsia requiring termination of the pregnancy. Histopathologic examination and DNA ploidy by image analysis were consistent with a twin pregnancy combining a complete hydatidiform mole and normal pregnancy.We hypothesize that this 1PN was at the origin of the hydatidiform mole. This case highlights the danger of transferring an embryo having 1PN.