EPIDEMIOLOGY AND HEALTH DATA INSIGHTS
Original Article
Mar 25, 2026 4 2

Sex Ratio of Live Births Following Fresh Versus Cryopreserved-Thawed Embryo Transfer in Invitro Fertilization: A Retrospective Study

Showunmi Olusheyi Solomon 1 2,
Omisakin Sunday Issac 3,
Aloy Okechukwu Ugwu 1 * ,
Ayeni Abraham Sunday 1 2,
Nwogu Chidimma Magnus 4,
Adefemi Ayodeji Kayode 5
1 Department of Obstetrics and Gynaecology, 68 Nigerian Army Reference Hospital, Yaba, Lagos, Nigeria2 Nigerian Army Medical Corps, Abuja, Nigeria3 Department of Obstetrics and Gynaecology, College of Medicine, University of Lagos, Nigeria4 Assisted Conception Center, Kingswill Specialist Hospital, FESTAC Town Lagos, Nigeria5 Department of Obstetrics and Gynaecology, Lagos State University Teaching Hospital, Ikeja, Lagos, Nigeria* Corresponding Author
Epidemiology and Health Data Insights, 2(2), 2026, ehdi032, https://doi.org/10.63946/ehdi/18234
Publication date: Mar 25, 2026
Full Text (PDF)

ABSTRACT

Background: Human sex is genetically determined at fertilization; however, emerging evidence suggests that assisted reproductive technologies (ART) may influence the secondary sex ratio (SR). Factors related to parental characteristics, laboratory practices, and embryo handling have been implicated, though findings remain inconsistent. This study aimed to compare the secondary sex ratio of live births following fresh versus frozen–thawed single blastocyst transfer.
Methods: We conducted a multicenter retrospective cohort study reviewing IVF records from Kingswill Specialist Hospital, Lagos, and referrals to the 68 Nigerian Army Reference Hospital and Lagos University Teaching Hospital. Records from 1 January 2017 to 31 December 2025 were assessed. Women who achieved live birth following single blastocyst transfer in either fresh or frozen–thawed IVF cycles were included.
Results: Of 159 records screened, 144 met eligibility criteria and were analyzed (72 fresh and 72 frozen–thawed cycles). Fresh embryo transfer was associated with a higher proportion of male live births compared with frozen–thawed transfer (69.4% vs 45.8%), whereas frozen–thawed cycles yielded a higher proportion of female infants (54.2%).
Conclusion: Fresh single blastocyst embryo transfer was associated with a higher male-to-female live-birth ratio compared with frozen–thawed blastocyst transfer, despite transfer at an equivalent developmental stage. These findings suggest that embryo cryopreservation may be associated with differences in sex ratio following IVF.

KEYWORDS

Sex Ratio Fresh IVF Frozen-Thawed Embryo Maternal Age Body Mass Index

CITATION (Vancouver)

Solomon SO, Issac OS, Ugwu AO, Sunday AA, Magnus NC, Kayode AA. Sex Ratio of Live Births Following Fresh Versus Cryopreserved-Thawed Embryo Transfer in Invitro Fertilization: A Retrospective Study. Epidemiology and Health Data Insights. 2026;2(2):ehdi032. https://doi.org/10.63946/ehdi/18234
APA
Solomon, S. O., Issac, O. S., Ugwu, A. O., Sunday, A. A., Magnus, N. C., & Kayode, A. A. (2026). Sex Ratio of Live Births Following Fresh Versus Cryopreserved-Thawed Embryo Transfer in Invitro Fertilization: A Retrospective Study. Epidemiology and Health Data Insights, 2(2), ehdi032. https://doi.org/10.63946/ehdi/18234
Harvard
Solomon, S. O., Issac, O. S., Ugwu, A. O., Sunday, A. A., Magnus, N. C., and Kayode, A. A. (2026). Sex Ratio of Live Births Following Fresh Versus Cryopreserved-Thawed Embryo Transfer in Invitro Fertilization: A Retrospective Study. Epidemiology and Health Data Insights, 2(2), ehdi032. https://doi.org/10.63946/ehdi/18234
AMA
Solomon SO, Issac OS, Ugwu AO, Sunday AA, Magnus NC, Kayode AA. Sex Ratio of Live Births Following Fresh Versus Cryopreserved-Thawed Embryo Transfer in Invitro Fertilization: A Retrospective Study. Epidemiology and Health Data Insights. 2026;2(2), ehdi032. https://doi.org/10.63946/ehdi/18234
Chicago
Solomon, Showunmi Olusheyi, Omisakin Sunday Issac, Aloy Okechukwu Ugwu, Ayeni Abraham Sunday, Nwogu Chidimma Magnus, and Adefemi Ayodeji Kayode. "Sex Ratio of Live Births Following Fresh Versus Cryopreserved-Thawed Embryo Transfer in Invitro Fertilization: A Retrospective Study". Epidemiology and Health Data Insights 2026 2 no. 2 (2026): ehdi032. https://doi.org/10.63946/ehdi/18234
MLA
Solomon, Showunmi Olusheyi et al. "Sex Ratio of Live Births Following Fresh Versus Cryopreserved-Thawed Embryo Transfer in Invitro Fertilization: A Retrospective Study". Epidemiology and Health Data Insights, vol. 2, no. 2, 2026, ehdi032. https://doi.org/10.63946/ehdi/18234

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