Clinical outcomes after single-versus double-embryo transfers in women with adenomyosis: a retrospective study.

BACKGROUND Adenomyosis affects the outcomes of spontaneous fertility and assisted reproductive technology. The single blastocyst embryo transfer (SBT) policy is an effective strategy known to minimize the risk of multiple pregnancy for non-adenomyosis women. However, little is known about its applicability to women with adenomyosis. The purpose of this study is to compare pregnancy outcomes between SBT, double-blastocyst embryo transfer (DBT), single-cleavage-stage embryo transfer (SET) and double-cleavage-stage embryo transfer (DET) in the frozen-thawed embryo transfer cycles among adenomyosis patients. METHODS This retrospective study was conducted in all frozen-thawed autologous embryo transfer cycles. 393 frozen-thawed embryo transfer cycles performed in adenomyosis patients were enrolled. The major clinical outcomes were implantation rate (IR), clinical pregnancy rate (CPR), miscarriage rate (MR), multiple pregnancy rate (MPR) and live birth rate (LBR). RESULTS  The SBT and DBT groups achieved higher IR (P < 0.001), CPR (P = 0.017), LBR (P = 0.040) and lower MR (P = 0.020) than the SET and DET groups. But the SBT and DBT groups achieved similar CPR and LBR. The SBT and SET groups achieved lower MPR (P < 0.001) than the DBT and DET groups. The average birth weight (BW) of SBT groups was higher than the DBT and DET groups (P = 0.016). When compared with SBT group, low-birth-weight infants were significantly higher with DBT and DET. CONCLUSIONS When performing frozen-thawed embryo transfer cycles among adenomyosis patients, the SBT group has similar IR, CPR, MR, LBR but lower MPR compared to the DBT group. Therefore, SBT might be offered as standard practice.