Small-sized follicles could contribute to high-order multiple pregnancies: outcomes of 6552 intrauterine insemination cycles.

RESEARCH QUESTION: Can predictors of twin and high-order multiple pregnancy among women with multiple cycles of ovarian stimulation intrauterine insemination (IUI) be identified?

DESIGN

Retrospective cohort study of IUI cycles carried out between January 2014 and December 2015 in a private clinic in Spain. The 4879 women and 6552 cycles analysed in this study include single IUI with ovarian stimulation using recombinant FSH.

RESULTS

Number of follicles and follicle size were the only factors with a significant effect (P < 0.001) on the likelihood of achieving a twin or multifetal pregnancy. Follicles 12 mm or wider greatly increase the chances of achieving a twin or multifetal pregnancy. A total of 73 out of 127 (57.5%) twin pregnancies occurred in cycles with at least one additional follicle measuring 12 mm or wider, and 102 out of 127 twin pregnancies (80.3%) occurred in cycles with at least one additional follicle measuring 14 mm or wider. Cancellation criteria should consider the presence of follicles 12 mm or wider.

CONCLUSION

Follicles measuring 12 mm or wider increase the risk of having a twin or a high-order multiple pregnancy rate. These data may help clinicians balance decision-making between cancelling and performing the cycle within an IUI procedure.