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 intrafaliopian transfer.

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EDITORIAL COMMENT: How have we done so well in preventing maternal deaths from pulmonary thromboembolism when most deaths from this cause are judged to be unavoidable? The number of maternal deaths from thromboembolism in Australia has fallen 90% in the 7 reported triennia! 44 (1964-19661, 43 (1982-1984). The remarkable reduction in the death rate has continued although the Caesarean section rate, an acknowledged contributing cause, hm continued to increme. How important is the reduction in the number of grand multiparas? I n high risk patients (previous deep vein thrombosis, previous pulmonary thromboembolism) prophylactic therapy (aspirin, anticoagulation with heparin or warfarin) is indicated during pregnancy and for about 6 weeks after delivery. but prophylactic anticoagulation therapy in all patients having Caesarean section, in theEditor's opinion, is definitely not indicatedwhen he was a Resident Medical Officer at the Royal Women's ffospital, Melbourne, in 1957, routine prophylactic an-