The incidence of ectopic/heterotopic pregnancies after blastocyst-stage frozen-thawed embryo transfers compared with that after cleavage-stage: a Society for Assisted Reproductive Technologies Clinical Outcomes Reporting System study.

OBJECTIVE

To investigate whether there is a difference in the ectopic/heterotopic pregnancy rate of blastocyst-stage frozen-thawed embryo transfers (FETs) compared with that of cleavage-stage FETs.

DESIGN

A retrospective cohort study.

SETTING

Not applicable.

PATIENTS

Women undergoing autologous FETs at either the blastocyst stage (n = 118,572) or the cleavage stage (n = 117,619), as reported to the Society for Assisted Reproductive Technology from 2004 to 2013.

INTERVENTIONS

None.

MAIN OUTCOME MEASURES

Pregnancy outcomes, specifically ectopic pregnancy rates and heterotopic pregnancy rates.

RESULTS

Among those who became pregnant, there was a significantly lower incidence of ectopic/heterotopic pregnancies in blastocyst-stage FETs versus that in cleavage-stage FETs (0.8% vs. 1.1%). The differences in ectopic/heterotopic pregnancy rates remained statistically significant after controlling for confounders such as tubal factor infertility and number of embryos transferred.

CONCLUSIONS

Blastocyst-stage FET was associated with a lower ectopic/heterotopic pregnancy rate compared with cleavage-stage FET.