Five per cent of babies arrive on the day they are expected. Ideally you should allow two weeks either side of your due date. Giving birth anywhere between 37 to 42 weeks is considered normal.
When you first see your midwife or doctor they give you a date that your baby is due. Sometimes this date is changed during the course of your pregnancy, but mostly it stays the same and is looked forward to with great anticipation. The reality is however that only five per cent of babies arrive on the day they are expected. Ideally you should allow two weeks either side of your due date. Giving birth anywhere between 37 to 42 weeks is considered normal.
There is evidence to suggest that the current methods of estimating the due date may in fact not be as accurate as we think. One study found first time mothers gave birth on average 5 days over their due date and second time mothers gave birth on average 2 days after their due date. Most studies I reviewed suggested that first time mothers had longer pregnancies than women who had a baby before.
Around 10 per cent of pregnancies do go beyond 42 weeks. When this occurs it is known as post-term or a prolonged pregnancy. Concerns regarding problems with the baby increases after 42 weeks. While research findings are contradictory about the risks of post-term pregnancy, it is generally accepted that there is an increase in the death rate of babies over 42 weeks. Part of this increase is thought to be due to babies with malformations – as these babies have a tendency to go overdue. In the majority of cases the outcome is good for prolonged pregnancies. It’s only a minority of cases where problems occur.
Commonly induction of labour is offered once the pregnancy exceeds 41 weeks. Research has found that induction of labour at this time slightly reduces the number of babies who die and decreases the chances of the baby passing meconium (the baby’s first bowel movement) into the amniotic fluid. Induction of labour before 41 weeks is not supported by research.
How can I avoid going overdue?
We have not got very much control over the actual length of pregnancy, when waiting for labour to start naturally. Each woman and baby are biologically tunned for a certain length of pregnancy. Some women find their mother and other relatives routinely go two, three or more weeks over due. They themselves may be predisposed to a longer pregnancy.
However a number of alternative strategies have emerged that are aimed to stimulate labour, with varying degrees of success. Here are some of the commonly recommended strategies:
- Sweeping membranes – during a vaginal examination the midwife or doctor gently separate the membranes from the opening of the uterus.
- Sexual activity – A woman’s orgasm causes oxytocin to be released, as does nipple stimulation. Oxytocin is the hormone that causes the uterus to contract. Semen also contains prostaglandins, which can help soften the cervix.
- Acupuncture or acupressure – consult a qualified practitioner
- Homeopathic remedies – consult a qualified practitioner
- Herbal preparations – consult a qualified practitioner
- Good hot bowl of curry
Avoid using castor oil. Castor oil can cause cramps, nausea, vomiting and spasmodic contractions of the uterus. Basically it is down right unpleasant.
If I choose to wait for labour to start naturally, what tests are available to check my baby’s wellbeing?
There are a number of tests offered to women who go ‘overdue’. Unfortunately the research evidence on the benefits or otherwise of the tests is inconclusive. While the tests may pick up a problem, there is not a lot of evidence to say these tests actually improve outcomes of a postdate pregnancy.
The following tests may be available.
- Fetal Movement Counting: A baby who is well moves frequently. A baby who is unwell (or compromised) may decrease the number of movements they make. Counting baby’s movements is a simple way to ensure that the baby is moving adequately and hopefully will pick up babies who aren’t doing so well. A baby who decreases their movements can be assessed further by other tests (see following points). Even though this is an easy and non-invasive test, current research hasn’t found that formal fetal movement counting improves the outcome of pregnancy.
- Non-stress test: A baby can be electronically monitored by a CTG (cardiotocograph). A CTG is where the baby’s heart rate is monitored along with any contractions of the uterus. A print out of the baby’s heart rate and contractions is made and compared. A CTG can assess the health of the baby at that point in time that the test is taken. A CTG cannot predict the health of the baby in the future.
- Amniotic fluid index: Pockets amniotic fluid are assessed by ultrasound and an overall score is given. If there is adequate amniotic fluid present, it can indirectly indicate that the placenta is functioning adequately. Assessment of amniotic fluid is usually combined with a non-stress test.
- Biophysical profile: Ultrasound is used to do the biophysical profile. Four factors are checked on ultrasound: Baby’s breathing, baby’s muscle tone, baby’s body movement and the amount of amniotic fluid. A score is given on these four factors. A non-stress test is also performed. If the result is good, a retest is usually recommended in a few days. A biophysical profile can better predict the health of the baby than a non-stress test alone, but its use does not improve the outcome for the baby.
If I choose to be induced, what methods are available?
There are three main methods of induction of labour. These methods include:
- Breaking the waters: The waters are broken with an instrument shaped like a large crochet hook. The cervix needs to be open a couple of centimetres before the bag of waters can be broken. Breaking the waters can be an uncomfortable procedure, particularly if the cervix isn’t open very far. Breaking the waters may be enough to start labour on its own, but usually a Syntocinon intravenous infusion is required.
- Prostaglandin gel: Prostaglandin gel is placed in the back of the vagina and helps soften and ripen the cervix. In some women, labour may start without further intervention. Prostaglandin administration increases the risk of developing a temperature, diarrhoea, fetal distress and haemorrhage after birth.
- Syntocinon through an intravenous infusion: Once the waters have been broken, an intravenous drip containing the drug Syntocinon can be used. Syntocinon is a synthetic hormone that makes the uterus contract and is a fairly reliable method for starting labour. Problems associated with induction with Syntocinon include failure to progress (resulting in a caesarean birth), increased need for pain relieving drugs, need for continuous monitoring of the baby through labour, increased risk of baby becoming distressed and increased risk of haemorrhage after the birth.
My doctor has said that she would like to do an internal exam and sweep my membranes to help bring on labour. Can you tell me more about this?
Sweeping the membranes (or ‘strip and stretch’ as it’s sometimes called) is where the midwife or doctor conducts a vaginal examination and separates the membranes from the opening of the uterus with their fingers. Sweeping of the membranes before or on your due date can help decrease the chance of your pregnancy going beyond 42 weeks and the need for an induction. The procedure its self can cause discomfort and women often report some vaginal bleeding and irregular contractions afterwards.
(30th August 2001)