Factors affecting occurrence of twin pregnancy after double embryo transfer on day 3

The aim of this study was to identify the risk factors of twin gestation in fresh double day-3 embryo transfer cycles.

Out of a total of 386 cycles of fresh double embryo transfers on day 3 between 2006 and 2013 at a single center, 72 women with single intrauterine gestational sac (GS) (single-GS group) and 32 women with double GS (double-GS group) were identified. The patients' clinical characteristics and laboratory results were extracted from electronic medical records and were compared.

The double-GS group had a significantly younger age (P = 0.012), and higher bodyweight (P = 0.033) compared with the single-GS group. The total number of blastomeres (P = 0.013) and cumulative embryo score (P = 0.012) were higher in the double-GS group. By receiver-operator curve analysis, maternal age ≤ 35 years, maternal bodyweight > 60 kg, total number of blastomeres > 14, and cumulative embryo score > 49 were the cut-off values to predict twin pregnancy. Among eight women with all four risk factors, the twin pregnancy rate was 87.5%. There was no twin pregnancy among seven women with no risk factors.

Younger age, higher bodyweight, and better embryo quality are all associated with a higher incidence of twin pregnancy after double embryo transfer on day 3. Single embryo transfer might be advisable for couples with risk factors for twin pregnancy.