The study was designed to evaluate the isolated effect of high serum oestradiol concentration on human chorionic gonadotrophin (HCG) day in IVF cycles on endometrial receptivity and placentation. A retrospective cohort included all women attending the IVF unit in 2006 and 2007, with the best prognosis to achieve pregnancy: age (<38 years), less than three IVF cycles, transfer of two highest grade embryos and no evidence of factors known to impair implantation or that are associated with increased risk of pregnancy complications. The total included 280 patients were categorized into three groups according to their serum oestradiol concentration on HCG day: group 1, oestradiol <5000 pmol/l, group 2, oestradiol in the range 5000-10,000 pmol/l and group 3, oestradiol in the range of 10,000-15,000 pmol/l. No significant differences were found between the groups in implantation, pregnancy and abortion rates. The high oestradiol group was characterized by high rate (20.8%) of pregnancy complications related to abnormal placentation--fetal growth restriction, pregnancy-induced hypertension and abnormal implantation of the placenta. Hence, the decision to perform embryo transfer in high-responder patients should take into consideration both possible risks of ovarian hyperstimulation syndrome and pregnancy complications related to abnormal placentation.

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