Calculating your due date isn’t an exact science: only 12 per cent of babies are born on the day they’re expected. Here’s what you need to know if your baby arrives early or late.


We all know how long pregnancy lasts for, don’t we – nine months, right? Wrong: in fact, a much more realistic estimation of your due date would be anywhere between 37 and 42 weeks after conception.

Indeed, according to the NHS’ most recent figures, about 89 per cent of deliveries occur between 37 and 41 weeks of gestation.
But even if your waters break before 37 weeks, or your baby still hasn’t arrived by 42 weeks, there’s no need to panic. Both you and your baby will be monitored closely as a matter of course and help is at hand for every individual birth.

Early births

Babies born before 28 weeks are actually a rarity, and many mums-to-be who suspect they’re going into premature labour discover that it’s a false alarm.

Sometimes doctors will be able to stop a premature labour (using drug treatment) to allow the mum to carry to term. In fact, only about a third of women who go into premature labour will deliver prematurely.

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A baby is considered premature (or preterm) if he is born before 37 weeks. But BLISS, the premature baby charity, breaks this down further:

  • 35-37 weeks as moderately premature
  • 29-34 weeks as very premature, and
  • before 29 weeks as extremely premature.

"Unless your baby is extremely premature, there are likely to be no long-term health problems,” says a spokesperson for BLISS.
“The vast majority of premature babies go on to live healthy lives that are no different from those of their peers.”

Dr Ronald Lamont, consultant obstetrician and gynaecologist and spokesperson for the Royal College of Obstetricians and Gynaecologists (RCOG) agrees. “We don’t get worried about serious health issues for premature babies until they get below about 34 weeks of gestation,” he says. “Fifty per cent of all preterm births occur after 35 weeks, and after this point it doesn’t cause a lot of problems really. There may be a few difficulties with jaundice and feeding but, other than that, not much.”

Going overdue

Your baby’s gestation should usually be around the 40-week mark, but don’t worry if your pregnancy goes beyond this. In fact, if everything’s going well with your pregnancy, your obstetrician will give you another 10 or 12 days beyond your due date before suggesting induction.

According to Dr Lamont, “When you are overdue, the benefits of going into natural labour outweigh the risks of becoming a little overdue. Really, you cannot beat natural labour. A normal delivery is best for the mother and best for the baby. However, your limit will probably be 10 to 12 days beyond the due date. Any longer than this is referred to as ‘post maturity’ (or prolonged pregnancy) – a pregnancy that exceeds 42 complete weeks (294 days) after the last menstrual period. After this point, your obstetrician will usually suggest that you be induced.

Induction is recommended because there is no reliable way of monitoring babies after 42 weeks. Your doctor will continue to keep an eye on things, taking into consideration factors such as the baby’s movements, the growth of the baby and the amount of fluid around him.


Mum's story

"My first baby had to be induced"

Despite having had my due date in my head as the Big Day for months, in the end it just came and went! There was just a feeling that my baby suddenly felt much heavier btu not much other movement. I went to the 40 week check up and the midwife suggested we try to do a ‘membrane sweep’ but it didn’t work and in the end I had to be induced. I didn’t really want it, but actually it just nudged me into labour and the birth was still completely natural after that.
Julia, 34, mum to Suki, 6 months