Pregnancy going overdue

Only five per cent of newborns arrive on schedule. Here’s everything you need to know about your due date – and what happens if you go overdue

From the moment you find out that you’re pregnant, one magical date is fixed in your mind – your baby’s due date. But did you know that only five per cent of babies arrive ‘on time’ at exactly 40 weeks? Eighty per cent arrive within 10 days either side of their due date (usually later), and the rest miss their window altogether.

‘Term babies are those who arrive any time between 37 and 42 weeks, not just on one specific date,’ explains Anne Deans, M&B obstetrician. ‘That’s human reproduction for you – pregnancies are simply not all the same length!’

Why might my EDD change?

Your doctor will calculate your estimated due date (EDD) when you ‘book in’, adding 280 days from the first day of your last menstrual period (LMP). They do this because, although people talk about pregnancy lasting nine months, in reality, a baby actually takes 10 ‘lunar’ months – consisting of 28 days each – to develop.

The problem with this system is that it relies on your menstrual cycle being 28 days long. In reality, cycles vary tremendously – some are shorter, others longer. If yours is longer than 28 days, your pregnancy will probably last more than 40 weeks.

If you’re not certain of the date of your LMP, a dating scan is the most accurate way of finding out how many weeks you are, although there is still some leeway either side. ‘A scan in the first 20 weeks of pregnancy can accurately produce your due date, with 80 per cent of babies arriving within 10 days either side, and 66 per cent of those arriving in the 10 days after the due date,’ says Anne.

Going past your EDD is normal, especially for first-timers. And if you’re expecting your second child and your first was overdue, it’s extremely likely that he too will come late. ‘Prolonged pregnancy is more likely if it has happened to you before,’ confirms Anne. 

A due week instead of a due date?

If EDDs are so inaccurate, why do we still classify pregnancy as 40 weeks? In France, they have now added an extra week, to bring it to 41. In the UK, medical experts have considered giving women a ‘due week’ but it doesn’t seem to be either practical or popular, according to Anne.

‘Doctors and midwives have tried giving a “due week” or “due window” but this is impractical when important documents such as maternity certificates have to be filled in, and when maternity pay is calculated. It’s also unpopular with expectant mums, who prefer to have a date to focus on.’

Concentrating on a particular date can, however, cause a lot of stress. Even before your EDD, friends and relatives will start phoning to see if anything has happened yet – and the calls will escalate once your due date has been and gone.

To take your mind off things, arrange some treats for around your EDD – lunch with friends, a manicure or a haircut. If you need to cancel, people will be more than understanding.

What if he comes too early?

Although most babies – especially first children – tend to keep their mums waiting, seven per cent arrive prematurely (before 37 weeks), according to BLISS, the charity for premature babies. There’s often little warning and no reason for an early delivery, although some potential complications, such as a weak or incompetent cervix (which tends to open too soon) or an abnormally shaped womb, can be detected in pregnancy.

It’s difficult to prevent a premature delivery, but there are a few precautions you can take. If you’re underweight, your risk of delivering early increases, so eat a healthy, balanced diet for your sake and your baby’s.

Smoking and drug use are linked to premature births so seek help in stopping these activities. Heavy physical work and extreme stress can also bring on early labour, so, wherever possible, avoid these situations.

Your baby is likely to need some special care (help with breathing and feeding, for example). But these days, premature babies stand a better chance than ever. Half of all babies born at 25 weeks will survive, and an amazing 80 per cent of those born weighing a tiny 1kg (2lb 2oz) will survive – a typical weight for a baby born at around 28 weeks.

What if I go overdue?

If you go past your due date, you’ll have an extra antenatal appointment at 41 weeks, where your midwife might do an internal examination to see if your cervix feels ‘ripe’ for labour.

She may also offer to do a ‘stretch and sweep’ – sweeping her fingers around your cervix to separate the membranes from the uterine wall. It can be uncomfortable, but you’ll be able to go home immediately afterwards. You may experience cramps and a show and, if the sweep is effective, labour normally starts within 48 hours.

If nothing happens, an induction is normally offered. This is because the placenta gradually begins to work less effectively, and the risk of stillbirth increases slightly. ‘Nine in every 1000 pregnancies lasting more than 42 weeks will end in stillbirth, compared to five births in every thousand between 37 and 42 weeks,’ says Anne Deans. One in five women has labour induced, so it’s not an unusual occurrence.

But before you agree to an induction, discuss the pros and cons with your midwife or obstetrician. There are other options, such as asking to have your pregnancy monitored every two to three days by listening to your baby’s heartbeat, to check that he’s OK. ‘But in my experience,’ says Anne, ‘I find that expectant mums are only too ready to be induced, as they become very uncomfortable as time ticks on.’

What does an induction involve?

There are several ways to induce labour, and you may need more than one to get things successfully established.

Pessaries: Pessaries containing prostaglandins (hormones that encourage your cervix to ripen and dilate) are placed in your vagina. Your baby’s heartbeat will be monitored at first to ensure that he’s coping but once labour is established, you’re normally allowed to remove the monitor so you can be mobile. It might take more than one dose of pessaries to get labour going, and they only work for around 50 per cent of women. The other half will need additional help, such as…

Breaking the waters (artificial rupture of the membranes): If your cervix is slightly open, the midwife can use a long hook to gently burst the bag of waters. This often stimulates the onset of strong labour.

Syntocinon drip: Syntocinon is an artificial form of the hormone oxytocin, which makes your womb contract. It is administered by drip, and the levels are gradually increased to mimic the amount of oxytocin you’d have in your body if labour had started spontaneously.

The contractions can quickly become very strong, intense and rapid, so talk to your midwife or obstetrician about pain relief before syntocinon is given.

Does induction mean intervention?

Induction can lead to intervention, such as a forceps or ventouse delivery or a caesarean. ‘Labours occurring after 42 weeks tend to be more problematic, with a higher chance of fetal distress and increased risk of needing a caesarean if your baby is large,’ confirms Anne Deans.

According to research, about 15 per cent of induced labours result in a caesarean. However, it is possible to have a natural vaginal delivery after an induced labour, especially if you make an effort to keep active – and if you’ve already had a vaginal delivery before, labour is much more likely to be straightforward.
 
Natural ways to kick-start labour

Curries: Some people think that a hot curry that gives you an upset stomach can help trigger labour. One of the first signs of natural labour is often a short bout of diarrhoea – the cervix and part of the bowel have a common nerve supply and, as your cervix becomes more active, the bowel is stimulated, causing faster movement of food and more frequent, looser bowel motions.

But a nasty tummy upset will only bring on labour if it was about to start naturally anyway. And the side effects of trying to start labour in this way can be very unpleasant. Tummy cramps, uncontrollable diarrhoea and contractions – no thanks!

Long walks: Rumour has it that walking makes your baby’s head press against your cervix, triggering labour. No-one knows if this is true or not, but staying active in late pregnancy keeps you fit and well and can give you stamina for labour.

Sex: Semen contains prostaglandins that help to soften the cervix. Having sex two or three times over a couple of days could help get things started if you’ve already gone past 40 weeks, but only if your body is ready.

Eating pineapple: Pineapples contain an enzyme called bromelain, which helps produce prostaglandins. However, there are various types of prostaglandins and each has a specific effect on a different part of the body. The type you need for labour isn’t the type that bromelain allegedly boosts, so eating pineapple probably won’t do much to bring on contractions.

Nipple stimulation: By stimulating your nipples one at a time, you can help your body release oxytocin, the hormone that plays a major role in labour. If you do this just before you’re ready to go into labour, the hormone could help kick-start contractions. Don’t stimulate both nipples at once – some studies have suggested this produces too much oxytocin and could cause fetal distress.