Induction of labour is a medical intervention used to stimulate the body to start labour. A woman can be induced by administering her drugs, breaking her water – also known as rupturing the membranes – or using alternative therapies.

Labour may be induced before term or before spontaneous labour begins for a number of reasons. Most commonly, a woman who has not gone into labour after a certain number of days past her due date is induced. Her baby is then considered a post term infant – most commonly defined as a baby born fourteen days after the expected date of delivery.

Commonly, although not always medically justified, doctors induce women one week or less after their due date, not giving the mother the chance to go into spontaneous labour.  In Bangalore, we have received reports of some doctors insisting on inducing labour on the due date itself, a troubling trend given that ultrasonic estimation of gestational age is still an inexact science and that induction of labour is – ironically -- a significant and growing cause of prematurity.

From 2.2% to 10.4 % of all term pregnancies last beyond the given due date. Evidence suggests that when an ultrasound dates a baby at 41-plus weeks, the likelihood of the onset of spontaneous labour is 60% within the next 3 days and 90% within a week. Based on the same information, the likelihood of a post term baby being a stillbirth or resulting in neonatal death remains low.

Therefore, for low-risk women who opt to extend their pregnancy to 42 weeks, the likelihood of spontaneous labour is high and the risk of complications is low.

Many doctors feel that a prolonged pregnancy is linked to increased risk to the health of the baby. However, no available evidence shows at what point the risk increases and whether it increases steadily or suddenly. However, medical risk factors such as high blood pressure or diabetes increase the risk of illness and death in a postdate pregnancy. If those conditions are present, conservative management of the pregnancy is warranted.   

If you are concerned about your labour being induced because of going past your due date, talk to your doctor well in advance about his or her policy on inductions. To do this, simply ask your doctor what she routinely does when a woman has not gone into labour on her due date.  

There are risks to both a baby being born post maturity AND inducing labour.

Risks of a Baby Being Born after the Due Date

Foetal skull calcification. The bones in the skull of a foetus become harder as the foetus matures in the womb. A baby who is born near term has a softer skull and the bony plates of the skull actually move or mould together to fit through the birth passage. This moulding is the reason vaginally born babies often have cone-shaped heads. If a baby is born too long past its due date, the harder bones of the skull do not mould as easily. Hence, the mother and baby may experience a longer, more difficult labour, especially during the pushing stage.

Placental deterioration or placental insufficiency. The effectiveness of the placenta may deteriorate near the end of pregnancy. The functionality of the placenta plays a key role in foetal well being, and a deterioration of the placenta can compromise the transportation of oxygen and nutrients to the foetus, which can lead to poor fetal growth and, eventually, damage to the baby's organ systems or even stillbirth. This is rare, but it is not necessarily connected to the calendar. The placenta can begin to fail at any point in pregnancy, and part of good prenatal care is monitoring growth and fluid levels so we can act before the baby's reserves are drained. Induction of labor is advised —even a cesarean without labor—if the baby is in trouble, regardless of due dates. See section on "What to consider when assessing your baby’s health post dates" for more details.

Meconium aspiration. If a foetus is not receiving the amount of oxygen and nutrients it needs in the womb, it may excrete meconium (or poop) in the amniotic fluid as a sign it is stressed. If the baby then breathes in the meconium-stained fluid in the womb or upon delivery, a serious respiratory infection can result. In an otherwise healthy foetus, foetal distress and meconium aspiration caused by post-term pregnancy is less common than for babies who have underlying growth or neurological problems. Also, keep in mind that inducing labour with pitocin also increases the risk of meconium aspiration and foetal distress.   

Foetal death. This is the most serious complication attributed to postmaturity.  Only going beyond the due date is not associated with poor pregnancy outcome. Extreme postdates or postdates in conjunction with poor foetal growth or developmental abnormalities do increase the risk of stillbirth. However, if cases where the baby had restricted growth or birth defects are removed, there is no statistical increase in risk until a pregnancy reaches 42 weeks, and no significant risk until past 43 weeks. The primary "evidence" of a sharp rise in stillbirth after 40 weeks—often misquoted as "double at 42 weeks and triple at 43 weeks"—seems to come from one study based on data collected in 1958.( McClure-Browne, J.C. 1963)

The risks associated with induction.

Labours started artificially are more likely to end in caesarean section and a myriad of other interventions than labours that begin spontaneously.  For this reason, induction should be performed only when the benefits can be proven to outweigh the risks.

Induced labours may take longer than labours that start naturally.

Induced labours can be more painful. The increase in pain is due to the use of oxytocic drugs (pitocin), which cause very strong contractions.

Babies can become stressed. Babies are affected by induction because of the longer labour, the broken bag of water, which acts as a cushion for the baby against contractions, and the prolonged use of oxytoxic drugs.

Close monitoring of the mother and baby is required. Because the bag of water is broken and because of the strength of the contractions produced by a drug such as pitocin, which can lead to fetal distress, mother and baby are often monitored continuously through the labour and delivery. The use of continuous monitoring devices often means a mother is less free to move around and is often forced to lie in a bed on her back during labour and delivery.

Risk of caesarean sections and assisted deliveries increases. In the end, all of these interventions often have a cascade effect – one intervention necessitates the next – often resulting in either a caesarean section or an assisted delivery, using forceps or a vacuum (ventouse).

Risk of prematurity. Even with early pregnancy tests and ultrasounds, induction of labor remains one of the largest causes of prematurity. The range of error in ultrasonic estimation of gestation increases as pregnancy advances. Artifact and technician inexperience can multiply the inaccuracy. Many practitioners seem unaware of this error range or, alternatively, are unwilling to secondguess a due date "confirmed" by ultrasound, even when the woman's history and clinical assessment indicate a later due date. Hence, the woman may be induced, even though the baby is clearly several weeks early. Some people discount the danger of early induction as long as the baby is within the last month of gestation. But even minor degrees of prematurity can cause harm. Babies born before full maturity can suffer from breathing difficulties or transient tachypnea, requiring separation in the hospital. They may be more prone to meconium aspiration. They are at risk for hypoglycemia and may have trouble maintaining body temperature. They are at increased risk for nursing difficulties and feeding disorders. They can be more likely to suffer from colic and digestive disturbances. These problems can affect the early bonding experience and make family adjustments more difficult.

How is labour induced using medicine?

Various hospitals have slightly different methods to start labour artificially. For the most part, a combination of the following methods is used.

Prostaglandin agents. The prostaglandin gel or tablet is placed onto the cervix ripen or soften the cervix 12-24 hours before oxytocic drugs like pitocin are given by intravenous (IV) drip. This drug prepares the cervix for dilation. Prostaglandins also have an oxytocic effect that stimulates uterine contractions.  Certain women, like women with asthma or women who have had a previous caesarean section, may not be able to use prostaglandins for medical reasons.

Artificial rupture of the membranes. This is commonly preformed in combination with oxytocic drugs to induce labour. Normally the membranes or bag of water soften contractions and protect the baby against infection and the stress of contractions. During induction, the bag of water is broken to take away the cushion of the water on the cervix, replacing it with the increased pressure of the baby’s head directly on the cervix. Once the membranes are ruptured, a baby must be delivered within a set timeframe – usually between 12-24 hours, depending on the hospital.

Synthetic forms of the hormone oxytocin (Pitocin, Oxytocin). These drugs stimulate uterine contractions.  Oxytocic drugs are commonly used for inducing labour. An oxytocic drug infusion is given using an IV drip. The success of induction with oxytocin is better when the cervix is ripe or when a ripening agent such as prostaglandin gel is given beforehand. 

How is labour stimulated naturally?

The following methods do not require medical drugs.

Stimulation of membranes is also referred to as “stripping the membranes” or a “membrane sweep”. This procedure is done during a vaginal exam. The doctor or midwife inserts a finger in between the membranes (bag of waters) and the cervix and move his/her finger in a circle around the opening of the cervix. This separates the membranes from the lower uterine wall and releases a surge of prostaglandins in to the maternal circulation. It is also thought that the gliding membranes sliding back and forth against the lower uterine segment may stimulate contractions. If you have a low lying placenta this procedure may not be advisable.

Sexual intercourse can be used for both ripening the cervix and stimulating contractions.  A man’s semen contains prostaglandins to ripen the cervix and a woman’s orgasm causes uterine contractions that can trigger labour if the body is ready for labour anyway. As many women’s bodies are quite sensitive at the end of pregnancy, intercourse should be undertaken gently in a position comfortable to her. Intercourse can be repeated as many times as is comfortable to a woman. Contrary to popular belief, the baby cannot be harmed by intercourse. If the bag of water has broken, nothing should be inserted in the vagina and intercourse must be strictly avoided.

Nipple stimulation causes the release of natural oxytocin in the body, which can stimulate uterine contractions.  Nipples can be stimulated by oneself or a loving partner or by using a breast pump. You can stimulate nipples twice an hour for 5-10 minutes at a time for 12-24 hours if required. Nipple stimulation may or may not be effective in starting labour. Women in high risk categories should not attempt nipple stimulation.

Castor oil. No clear explanation exists for the reason drinking castor oil may help start contractions. However, drinking castor oil does cause women to pass loose motions. Castor oil may work by stimulating prostaglandin production from contractions in the bowel. Drinking two ounces of castor oil in a morning lassi or smoothie may or may not stimulate labour.

Acupuncture and acupressure. Western medicine has no clear explanation for why acupuncture or acupressure may help induce labour. In Eastern medicine, it is believed that acupuncture and acupressure unblock the flow of energy along certain meridians that are inhibiting labour.  Acupuncture is performed using small needles that are applied on the skin. Acupressure is performed by pressing ones fingers onto specific points on a woman’s body.  Scientific evidence for these two methods is not available, so the level of effectiveness is not known.

There is no clear evidence that supports one form of induction over another. Talk to your doctor about risks before any form of induction is undertaken.

What to consider when assessing your baby’s health post dates.

The aim of monitoring post-date pregnancies is to identify babies that are at risk from inadequate nourishment inside the womb, where induction is recommended. When monitoring demonstrates that foetal growth, activity and amniotic fluid levels remain within expected norms, the baby can safely wait for spontaneous labour to begin.

Review your due date, is it correct?

Women may be induced unnecessarily or may go unknowingly past their due date if there is a mistake in calculating their due date. If there is any confusion about the date of your last normal menstrual period before becoming pregnant, take an early (before 12 weeks) scan to estimate an accurate due date.  Generally, embryos grow uniformly in the first trimester. After 12 weeks or from the second trimester onward, foetuses vary in size due to characteristics of the biological parents. Therefore, only scans done in the first 12 weeks of pregnancy can be relied upon for dating the pregnancy.

Monitor your baby’s heart. The foetal heart rate is one of the best measures of a foetus’ well being. Tests examining the health of the foetal heart rate are commonly used in a post date situation to determine if the foetus is healthy enough in the womb to continue the pregnancy. These tests are referred to as Non-Stress Tests (NST) or Auscultated Acceleration Tests (AAT). In these tests, the doctor or technician listens to the foetal heart rate for a period of time – usually 15-20 minutes – and asks the mother to signal when foetal movement is felt within the womb. If the baby moves a number of times throughout the test and immediately after each movement the heart rate goes up, this is considered a healthy foetus or reactive test result. If the foetal heart rate does not increase significantly after each movement, the test has a non-reactive result, which can indicate the foetus is not well in the womb and further investigation is warranted.  

Measure the volume of the fluid around the baby. Low fluid in the amniotic sac (bag of water) is caused by decreased foetal urine production (Yes, amniotic fluid is mostly made up of foetal urine!). Low fluid in the amniotic sac indicates the foetus is chronically stressed from not receiving the nutrients and oxygen it needs from the placenta. In a post-date pregnancy, the placenta may no longer be functioning at an optimal level. Fluid around the baby is measured using ultrasound. If the fluid is sufficient, it is one sign that all systems are functioning normally even though the baby has not been born yet. If the fluid volume is low, that is a sign the pregnant body is not properly supporting the foetus anymore.

Monitor the blood flow to the baby from the umbilical cord. A crucial aspect of foetal well being is the rate of blood flow between the foetus and placenta. Ultrasound is used to measure the rate of blood flow through the umbilical cord. If the blood flow is disturbed in any way, the foetus does not receive the needed oxygen and nutrients. An ultrasound for blood flow may be done in conjunction with a larger test of foetal well being called the Biophysical Profile. A biophysical profile can combine the use of a Non-Stess Test and the use of ultrasound to look at a variety of things: foetal breathing movements, gross body movement, type of foetal movement, reactive heart rate, volume of amniotic fluid and the state (or grade) of the placenta. The combined measurements used in the biophysical profile differentiate the fully oxygenated and neurologically sound foetus from a foetus that is not thriving in the intrauterine environment.

Large studies have shown that monitoring pregnancy while waiting for spontaneous labour results in fewer caesareans without any rise in the stillbirth rate. When monitoring shows that foetal growth, activity and amniotic fluid levels remain within expected norms, in most cases, the mother and baby can safely wait for spontaneous labour to begin.

Augmentation of Labour

Augmentation of labour is the stimulation the uterus during labour to increase the frequency, duration and strength of contractions.

Augmentation is performed by using an infusion containing an oxytocic drug (pitocin) that is administered via IV drip continually into the patient’s arm, under close monitoring.

The main benefit of augmentation of labour is that it keeps the labour progressing when the mother or uterus is tired.

Without careful management, the greatest risk of augmentation of labour is hyperstimulation of the uterus, resulting in distress of the baby and in some cases uterine rupture.

Augmentation of labour with the use of oxytoxic drugs is often overused in busy labour wards where there is pressure to move women out of in-demand labour beds. In some cases, oxytoxic drugs are added to an IV without a woman being told. Discuss carefully with your doctor the necessity for and risks and benefits of augmentation of labour before any drugs are administered.