A 2026 retrospective study indicates that in vitro fertilisation-embryo transfer (IVF-ET) cycles performed in the spring might lead to more favourable outcomes. Researchers analyzed data from over 1,400 infertile patients undergoing IVF at the Affiliated Hospital of Southwest Medical University in China between 2019 and 2023.
While initial analysis showed no significant seasonal impact on general pregnancy rates, clinical outcomes, or live birth rates, further adjustments revealed a notably higher blastocyst formation rate in spring compared to summer. Specific years also demonstrated increased HCG positive rates and clinical pregnancy rates in spring, alongside improved blastocyst formation rates in spring and winter versus autumn in certain periods.
The study's authors propose that the "suitable environmental temperature" in spring could positively regulate oestrogen and progesterone secretion, enhancing endometrial blood flow and thickness. This, they suggest, creates a more favourable environment for embryo development, while lower winter temperatures might impede endometrial growth.