Seasonal distribution in conceptions achieved by artificial insemination by donor.

The distribution of conceptions after artificial insemination from a donor was studied in 259 conceptions at an artificial insemination clinic and found to be seasonal. Conception was not influenced by the number of donors or patients attending the clinic, the frequency of inseminations, or medical skill. Conception was more common from early winter until early spring (October to March) with a peak in November. As variables such as frequency of intercourse and ovulation were irrelevant in these women and highest sperm counts occur from February to March these results suggested a seasonal variation in the quality of the ovulated egg or endometrial receptivity. The waste of eggs after ovulation (or preimplantation conceptuses) at specific times of the year has implications in the treatment of infertility, particularly for in vitro fertilisation and gamete intrafallopian transfer.