The effect of breastfeeding on treatment outcomes in in-vitro fertilization frozen embryo transfer cycles

Purpose While breastfeeding is known to impact unassisted conception, its effect on fertility treatment outcomes remains unclear. This study aimed to evaluate the effect of breastfeeding on in-vitro fertilization (IVF) frozen embryo transfer (FET) outcomes.

A retrospective cohort study at a single, urban, Canadian Fertility center, including women who underwent an FET(2015–2023). Breastfeeding women (study group) were compared to non-breastfeeding controls, matched 1:1 for age, treatment protocol, and year. We compared outcomes between the two groups. Primary outcomes were pregnancy rate (PR), clinical pregnancy rate (CPR),and live birth rate (LBR). Secondary outcomes included peak endometrial thickness prior to progesterone supplementation, biochemical PR and miscarriage rate. Multivariate logistic regression controlled for confounders. Two sub-analyses within the breastfeeding group examined treatment outcomes by breastfeeding duration (≤ 12 months; > 12 months) and prolactin levels (normal;elevated).

Overall, 118 women met inclusion criteria (59 breastfeeding, 59 controls). Breastfeeding women, compared to controls,were characterized by a younger median age at initial oocyte collection (34.8 years(31.9–37.11) vs. 35.85 years(33.2–39.2),p = 0.044); higher median parity (1(1–1) vs. 0(0–1), p < 0.0001);and higher rates of irregular cycles (35.59% vs. 18.64%,p = 0.016);and elevated prolactin levels (16.95% vs. 1.69%,p = 0.003). Utilizing multivariate logistic regression adjusting for breastfeeding status,parity, age at initial oocyte collection, and cycle regularity, only maternal age at oocyte collection was associated with PR (adjusted odds ratio 0.84, 95% confidence interval 0.75–0.94,p = 0.003). Both sub-analyses revealed similar PRs, CPRs and LBRs between groups.

Breastfeeding during an FET cycle was not associated with treatment outcomes, including PR,CPR, or LBR, providing cautious reassurance to physicians and patients. Similar content being viewed by others Data availability All data supporting the findings of this study are available within the paper.

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There are no acknowledgments to report Funding This research received no specific grant from public, commercial, or not-for-profit funding agencies. Author information Authors and Affiliations Contributions AH, UA, and WB designed the study and helped with data acquisition, analysis, and interpretation. AH, NK, VB, TS and ES participated in data acquisition, analysis, interpretation, and article revision for critical intellectual content. All authors contributed intellectually to the writing or revision of the manuscript, approved the final version, and are accountable for all aspects of the work. Corresponding author Ethics declarations Ethics approval This study was performed in line with the principles of the Declaration of Helsinki. The study received approval from the ethics committee of the McGill University Health Center (MUHC) Reproductive Center (MUHC REB 2024–10239). Informed consent Informed consent was waived due to the retrospective design of the study. Competing interest The authors have no relevant financial or non-financial interests to disclose. Additional information Publisher's Note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. Supplementary Information Below is the link to the electronic supplementary material. Rights and permissions Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law. About this article Cite this article Hochberg, A., Kugelman, N., Amikam, U. et al. The effect of breastfeeding on treatment outcomes in in-vitro fertilization frozen embryo transfer cycles. J Assist Reprod Genet 42, 2747–2754 (2025). https://doi.org/10.1007/s10815-025-03556-9 Received: Accepted: Published: Version of record: Issue date: DOI: https://doi.org/10.1007/s10815-025-03556-9