If you have the choice, do not take up an offer to induce labour. Picture: Jennifer Bruce

Washington - A new study came out recently linking autism to labour induction.

I will not get into that particular study right now, but it got me thinking again about labour induction, a topic that I cover at some length in my book Expecting Better.

When I was 39 weeks pregnant, my doctor offered to schedule an induction at my due date. This is common now, although that was not always the case. In 1990, fewer than 10 percent of births followed medical induction of labour; by 2009, this number had risen to 25 percent. This increase has occurred across the board, not just for babies who are overdue. In 1990, only seven percent of births at 39 weeks of pregnancy were induced, but 23 percent were induced by 2009.

Sometimes, labour is induced for medical reasons – the baby is not doing well or a condition threatens mom’s health. This, obviously, makes a lot of sense, and we are lucky to have the option. But this was not the case for me; my doctor was effectively offering an elective induction: I could choose to have the baby at 40 weeks, rather than wait for her to arrive on her own. And by 39 weeks I was definitely tired of being pregnant, and Penelope was plenty big. But still I said no, and here are the two reasons why.

First, the use of pitocin – the primary method of induction – may increase pain in labour. For anecdotal evidence on this all you have to do is go online: chat boards are full of women who have had spontaneous labour and an induction and report the latter was more unpleasant.

My mother had three children, all without an epidural, and reported that labour after she was induced with my youngest brother was the worst, despite the fact that he was the third kid.

Going beyond anecdotes, researchers find that women who are induced with pitocin are more likely to use an epidural; increased use of pain relief probably points to increased pain (at least before the epidural is administered).

Second, there is direct and indirect evidence that induction can increase the risk of a caesarean section. This seems to be most true when pitocin is used alone. Of course, C-sections are safe and common, but recovery from them still tends to be harder than recovery from a vaginal delivery.

These concerns are there for any induction – before or after 40 weeks. I was even more wary of pre-due-date induction. Some women like this idea – 37 weeks is full term, so why not get the baby out already? – but it is really not smart if not medically indicated.

It is true that babies who come on their own at 37 weeks do just as well as those who arrive on their own at 40 weeks. One good way to measure this is with the Apgar score. This is a number from zero to 10 that measures how well your baby is doing at birth – about 80 percent of babies get an Apgar of nine or 10, which means they are doing well, and a score of seven or below indicates some distress.

Among babies born on their own – no induction – at 37 weeks, about 2.4 percent of them have a low Apgar score. Among those born on their own at 40 weeks, this is about 2.3 percent; the difference is small.

But when we look at induced births, we see slightly larger differences.

For babies induced at 40 weeks, again the share with low Apgar scores is 2.3 percent, but for babies induced at 37 weeks, it is about 3 percent. This difference is small in magnitude but statistically significant.

This basic point is consistent with something that the American College of Obstetricians and Gynaecologists has been saying for a long time: that elective inductions should not be performed before 39 weeks. Basically, some babies are ready at 37 weeks, but that does not mean they all are.

Does this mean you should say no to an induction for medical reasons? No.

But it may mean that it is a good idea to stick it out for a few more days, to give your kid a chance to arrive in his or her own time. – Washington Post-Bloomberg

* Oster is an associate professor of economics at the University of Chicago Booth School. Her book is Expecting Better: Why the Conventional Pregnancy Wisdom Is Wrong.