The conventional wisdom on making babies is that the best time to try is between three days before the woman ovulates and about two days afterward. This standard advice--based on a decades-old survey of British couples--seems to be flawed, according to a new study by the National Institute of Environmental Health Sciences. A woman’s monthly fertile period is indeed around six days long, the study concludes, but it ends on the day of ovulation, when the egg is released from the ovary. Intercourse after that is very unlikely to lead to conception.
Why has it taken so long for scientists to discover this elementary fact of human biology? The way medical research works is that we’re pretty good at studying diseased people, but what happens in ordinary healthy people is much more elusive, says epidemiologist Allen Wilcox, one of the authors of the current study. One flaw in earlier studies ...
