No association between ageing gametes and birth defects

Authors of a research letter in this week’s issue of THE LANCET conclude that there is no evidence to support the belief that sexual intercourse too soon or two long after ovulation is associated with an increased risk of birth defects and Down’s syndrome.

For many years, the ageing of gametes as a result of prolonged retention in the female reproductive tract before fertilisation has been circumstantially associated with major birth defects. Joe Leigh Simpson and colleagues from Baylor College of Medicine, Houston, USA, studied over 1000 pregnant women from Chile, Colombia, Italy, and the USA, who had recorded the timing (with regard to presumed ovulation) of sexual intercourse leading to conception.

There were no significant differences in the proportion of birth defects in infants born to mothers who reported optimally timed conceptions (on the day of or one day before ovulation) than infants born to mothers who reported non-optimally timed conceptions (2.7% compared with 2.5%, respectively). There was also no significant difference in the proportion of infants born with Down’s syndrome (0.5% for optimally timed conceptions compared with 0.7% for non-optimally timed conceptions).

Joe Leigh Simpson comments: “Overall, our findings are reassuring for users of natural family planning, for couples who have intercourse episodically, or for