The British Medical Journal caused a stir last week by claiming that the growing trend for families to have babies later in life "defies nature and risks heartbreak". The increase in late babies was, apparently, an "epidemic".
My own family contains an epidemic of three children born after their parents were 35, so maybe I am biased. As a cheap opening shot, I would like to inform the BMJ that the purpose of medicine is to "defy nature", since mother nature herself is the prime architect of cancer, heart disease, and much else that doctors seek to eradicate. But I like to tell myself that the BMJ editorial really offended me because its language was unnecessarily emotive and missed a chance to inform couples, calmly and clearly, of the precise risks they are taking if they delay starting a family.
The papers cited in the BMJ editorial do indeed show that it is harder to have healthy babies after the mother reaches 35, and much harder after 40. But how much harder? And why? These are statistics that people need to understand before making their choices. The diatribe may have raised consciousness of the problem, but otherwise did not help people to make an informed choice.
Working on the basis that an approximate truth is better than a precise untruth, I have tried to calculate what might happen to 1,000 couples in their late 20s who spend two years trying to have a healthy baby, and have compared the outcome with another 1,000 couples in their late 30s and a further 1,000 in their early 40s. I admit that the numbers are far from certain, and involve some informed guesswork. But I have reasons, based on the evidence cited by the BMJ, for every number in the table.
Fertility drops sharply with age, so fewer older women even get to the starting gate of pregnancy. And the older you are, the more likely a miscarriage or ectopic pregnancy. You will probably need more medical intervention at delivery, and may be more likely to suffer the death of a baby just before or after full term. However, the chances of this remain remote (much less than 2%) even for women in their 40s.
Overall, because of the decline in fertility and rise in miscarriages, the number of successful births after two years of trying does drop sharply as parents get older. But maybe this just means that people have to try longer, or need medical help to get pregnant.
Certainly, it is wrong to suggest that women who conceive in their late 30s face a bad outlook. As one of the BMJ's most reputable citations concludes: "Perinatal mortality rates are low at all ages, especially in recent years." But you would never have guessed this from the emotive language in the BMJ editorial.
