Is time interval from breastfeeding cessation to frozen single euploid embryo transfer cycle associated with pregnancy outcome?

Objective: Prolactin (PRL) secretion during breastfeeding suppresses gonadotropin releasing hormone and ovulation. While PRL receptors are present in the endometrium, it is unknown whether transient rises in secretion during breastfeeding affects subsequent embryo transfer outcome. This study assesses whether the interval between breastfeeding cessation and initiation of a frozen single euploid embryo transfer (SEET) cycle is associated with live birth rates.

Methods: Patients who stopped breastfeeding within 12 months of SEET cycle from January 2012-September 2023 were included. Patients were grouped by time interval: Group 1: ≤ 1 month; Group 2: >1-3 months; Group 3: 4-6 months; Group 4: 7-12 months. Variables were compared between groups. Multivariate logistic regression was performed to compare odds of pregnancy, clinical pregnancy, clinical pregnancy loss, and live birth between groups.

Results: A total of 206 patients were included: 59 (28.6%) in Group 1, 56 (27.2%) in Group 2, 40 (19.4%) in Group 3, and 51 (24.8%) in Group 4. There were no differences in characteristics between groups. On univariate analysis, there was no statistically significant difference in live birth (Group 1: 55.9.%, Group 2: 53.6%, Group 3: 55.0%, Group 4: 58.8%, P = 0.958). When adjusted for variables, there continued to be no difference in odds of live birth with cessation of breastfeeding within 1 month of SEET compared to longer intervals. Secondary outcomes also showed no difference.

Conclusion: Breastfeeding prior to SEET does not appear to alter endometrial receptivity, as demonstrated by the lack of association between interval of cessation and live birth rates.