Fertility continues after age 40BMJ 1996; 312 doi: https://doi.org/10.1136/bmj.312.7036.975b (Published 13 April 1996) Cite this as: BMJ 1996;312:975
EDITOR,—The numerous women who have children in their fourth and fifth decades would hardly agree that “fertility declines at 30 and is almost gone by 40”—the alarming subtitle used by Roger Gosden and Anthony Rutherford in their otherwise reasonable editorial on delayed childbearing.1 In 1994, 8451 sets of twins were born in Britain, and the years between ages 35 and 40 are the peak period for twin and higher order births, whether these are the outcome of assisted conception techniques or not. At age 37 the incidence of dizygotic (fraternal) twins is roughly four times that at age 20.
As for the fifth decade, in Britain around 9000 babies a year are born to mothers over 40. Many of these pregnancies are unplanned and might well not have occurred had it not been for some well intentioned but misguided doctor advising his or her patient that a woman of her age “needn't bother” with contraception any more.
The authors mention the Hutterite community in North America, but the research to which they refer is itself over 40 years old. A natural onset of infertility is by no means the only possible reason for the low number of births to women over 40, since there are, as the authors themselves suggest, a multitude of other possible explanations despite the Hutterite ban on contraception.
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