It’s a mystery as to why, but for some reason in vitro fertilization (IVF) seems to be more successful if the eggs are harvested in the summer. The intriguing anomaly only applies to when the eggs are collected, not when they’re implanted.

And, the numbers are clearly seasonal. Specifically, live birth rates for summer-collected eggs are 31%, while the rates for eggs collected in the fall are only 26%. Winter and spring rates are in-between. The data were collected over eight years in Australia and included 3,657 frozen embryo transfers.

Even more puzzling, the temperature of the day doesn’t appear to have any effect, even though a different study in Boston found that eggs collected on the warmest days were 34% more likely to have a live birth. Success for Boston’s summer collection rates were also noticeably higher, at 42%.

SOURCE:

Science Alert July 10, 2023