LABOUR INDUCTION

Induction of labour (IOL) is called the artificial start of the labour process before it starts spontanesouly (by itself).

Women that have already delivered know that the hardest part of pregnancy is towards the final weeks of it. It is when the baby and the belly have grown enough to make it difficult for you to move around, sleep or perform simple tasks. Sometimes, you may reach a point of thinking or saying "Enough is enough!". Enought with the pregnancy, enough with the discomfort, the tiredness. Enough with the waiting of holding in your arms thw little creature that grows inside you for the past 9 months. Even if the idea of being induced might not please you, completing the pregnancy quickly, does sound appealing.

there are women that need to be induced. There are certain medical conditions, for example preeclamspia, where continuing the pregnancy poses more risks to the mother and the baby than having an induction of labour.

However, in a number of cases, IOL is chosen to accomodate either the mother or the doctor, with no apparent medical reasons for it. It has to be said that IOL is not a simple method and it certainly carries risks. Induction of labour should not be considered as a process in which we merely provide medication and the body will function in the anticipated way.

What every pregnant woman should know is that IOL means that we are trying to provoke a process not due to happen until some time later. Additionally, it means that there is no return: once we begin the process of delivery, that means that we are commited in completing the pregnancy one way or another. This is because, when consenting to an IOL, is like admitting that there are important reasons for which the baby has to be born. Therefore, the pregnancy is automatically classified as 'high- risk' even though everything was going fine until then.

Babies are satying in the womb for a reason: their complete and full development. We have to know that the last weeks of pregnancy are particularly important. Antibodies from the mother cross the placenta and make the baby stronger to fight infections after birth. The baby tops up its iron and fat stores and perfects the breastfeeding and swallowing reflexes. Brain development accelerates during the last 5 weeks of pregnancy. Finally, the baby's lungs continue to develop and some scientists relate that to the spontaneous start of labour. There is scientifical data suggesting that babies born at 40 weeks have a reduced risk of developin mental disorders compared to babies born at 38 or 39 weeks. It is also known that babies born too soon, have a greater probability of suffering from breathing problems, low blood sugar, jaundice, irregular heart beating and breastfeeding difficulties.

 

What is IOL?

When the labour starts spontaneously (by itself), a series of complicated natural events is triggered that include a woman's body and brain but also the baby itself. Scientific data suggest that the baby send signals that it's ready to be born and the mothers brain responds by secreting oxytocin. This hormone, during labour, causes the womb to contract and pushes the baby out. Its quantity is increasing gradually and not abruptly. Moreover, the womb itself becomes more responsive to oxytocin's action.

the artificial induction of labour bypasses two essentials steps of the process: the baby has not given the signal to begin the labour process and your body cannot respond in the same way it would respond if the natural labour hormones were secreted.

Weeks before the labour starts, the womb begins to wake up, little by little. Pregnant women are able to feel small contractions that last for a few seconds and are painless. These are the so- called preparatory or Braxton- Hicks contractions. This contractions are extremely useful in preparing the baby and the womb for labour: the baby gets into the proper position and the womb's cervix (the neck of the womb) gradually gets shorter, softer and begins to dilate.

With IOL, we are trying to replace the normal process that usually lasts for weeks and finish everything in hours. Because of the sudden and increased administration of hormones, the whole process is far more painful because we augment and accelerate the womb's contractions and also speeding- up the labour process. Induction of labour needs close monitoring of the mother and the baby, in the labour ward and with adeqaute administration of painkillers.

 

What are the indications of IOL?

  • The most important medical reasons for IOL are:
  • Preeclamspia before 37 weeks
  • Serious maternal ilness that does not respond to treatment
  • Serious but controlled vaginal bleeding
  • Choriomanionitis
  • Suspicion of fetal compromise
  • Rupture of membranes (waters break) in a full term baby and presence of Group B strep

 

Other possible medical reasons for IOL are:

  • Post term pregnancy. Pregnancy that exceeds 41 (or even 42) weeks
  • Diabetes mellitus (depending on the blood sugar control and the co- existence of complications)
  • Isoimunisation of the mother towards the end of the pregnancy
  • Intrauterine growth restriction (IUGR)
  • Reduced amniotic fluid (oligohydramnios) towards the end of the pregnancy
  • Pregnancy induced hypertension after 38 weeks
  • Intrauterine death
  • Rupture of membranes (waters break) in a full term or almost full term baby, without the presence of Group B Strep
  • Logistics, ie long distance from the maternity hospital or a history of very fast labour
  • History of intrauterine death in a previous pregnancy (for psychological purposes only, without any advantages on the overall health of the mother or the baby)

 

We will elaborate on the commonest reasons for IOL:

  • Post dates pregnancy (When the pregnancy is past the due date)

Babies considered full term are those that are born between 37 and 42 weeks. The estimated due date (EDD) is 40 weeks or 288 days after your last menstrual period. Accurately calculating the EDD is essential in order to better protect your baby. The most exact way of calculating the EDD is during the first trimester scan (nuchal scan) where the margin of error is only 1- 2 days.

Each pregnancy is different, but under no circumstances should the EDD mean that the pregnancy has to be completed. The EDD is not an expiry date! The pregnancy can safely be extended until the 41st week (or even the 42nd) as long as there are no risk factors.

Conflicting evidence exist about post dates and IOL: Some researchers claim that the risk for a caesarean is reduced with IOL, others claim that there is no differenceand, finally, there are others who believe that there is an incresed risk for a cesarean in women who have IOL. Obviously, that means that there are no conclusive data yet. For the moment, the world health organisation (WHO) suggests that a) IOL is indicated for those pregnancies that reach 41 weeks (a week after the EDD) and b) IOL is not recommended for pregnancies without any complications before 41 weeks.

 

  • Premature Rupture of Membranes (PROM)

When the amniotic sac ruptures before labour has started, this is called premature rupture of membranes. If the pregnancy is towards the end, we usually allow 24- 48 hours for contractions and labour to start by themselves. If that does not happen, we need to induce labour in order to avoid the risk of infections.

If the premature rupture of membranes happens even earlier, when the baby is still preterm, then we administer corticosteroids injections to the mother to induce the baby's lungs maturity. Ideally, we would like the baby to reach 34 weeks and then proceed with induction of labour. The mother- to- be needs to know that if the labour does not start by itself, there is still a substantial probability to have a cesarean section.

 

  • Suspicion of a large baby

The baby's size is determined by its genes but also from other conditions, such as gestational diabetes. We also know that ultrasound, in accurately estimating the baby's weight, is not very accurate. Therefore, we can only suspect that the baby might be large for gestational age, (LGA, macrosomic).

Macrosomia is when the baby's weight is more than 4,500 grams. According to others the definition is applicable also for babies heavier than 4,000 grams. Macrosomic babies are more prone to injury during birth as their shoulders might get stuck on their way out. This is called 'shoulder dystocia'. These babies are more susceptible to brachial plexus nerve injury (that is the nerve of the arm) or for bone fracture.

According to recent studies, there seems to be a (small) benefit if we induce labour on a suspected-to-be large baby because this way we can reduce the incidence of shoulder dystocia. Neither the probability of baby being injured, nor the need for a cesarean section is altered. However, there are other scientific societies and the World Health Organisation that do not accept suspicion of a large baby as a reason to induce labour.

If there is gestational diabetes that is well regulated, then pregnancy can continue until 40+6 weeks of pregnancy. The World Healt Organisation does not suggest labour induction for gestational diabetes (as the only condition) before 41 weeks of pregnancy.

 

  • Intrauterine Growth Restriction (IUGR) towards the end of pregnancy

Baby's growth during pregnancy depends from many factors: genes, your overall health nad how well the placenta works. IUGR babies are those babies that do not receive from the placenta all the necessary nutrients (and oxygen) that they need.

Again, it is crucial that babies are dated precisely and that can be achieved by the nuchal translucency scan, at the beginning of the pregnancy.

We can follow the baby's growth, estimating the weight but also with the Dopplers test that shows if the baby is adequately oxygenated or not. Moreover, cardiotocography can provide with additional information about the fetal well- being. If the baby's situation deteriorates, we can then suggest labour induction.

On the contrary, a study from Holland showed that in babies where there was suspicion of intrauterine growth restriction (IUGR), there was no clear advantage of a more aggresive induction policy over expectant management. In conclusion, women who choose not to have induction of labour, can continue their pregnancy with closer monitoring.

  • Reduced amniotic fluid

Reduced amniotic fluid (oligohydramnios) means that the fluid around the baby becomes less. The maniotic fluid is important in protecting the baby and offering the right type of environment for its development and growth. When it appears less, we have to identify if the reason for it is that the water broke. If this has not happened, then it might mean that the baby is under distress. We consider the amniotic fluid to be reduced when the amniotic fluid index (AFI), calculated by ultrasound is less than 5 or if the deepest pocket of amniotic fluid around the baby is less than 2 cm.

We need to know that data from quality research and meta- analyses have shown that induction of labour at the end of pregnancy for reduced amniotic fluid does not have any benefits, but only increases the incidence of operastive delivery and cesarean section.

 

How is induction labour done?

We will briefly discuss the commonest methods of labour induction. You may need to have one or more of them. It is extremely important that you are properly informed about the benefits and risks of each method and the exact reason for the induction. If there are clear benefits about the baby's health then the choice is obvious, but if you and the baby are not under any threat, it is worth to consider whether you would like to be induced or not.

1. Cervical examination and membrane sweeping

If the cervix (neck of the womb) is slightly open (dilated) then we can use the index finger and try to separate the sac membranes from the the womb walls. This is a medication- free method that has been proven to help the process of labour. Locally, substances (prostaglandins) are being produced. These substances can help softening and dilating the cervix. This method can cause, at that time, some discomfort or pain as well as some minor bleeding.

2. Synthetic prostaglandins

If your cervix is still hard, closed and long, that means that it needs to be softer, shorter and to start opening. This can be achieved by using medications that are placed deep in your vagina, close to the cervix. This way they can induce changes in the cervical stucture. In case one dosage is not enough, we can repeat administration in order to have the desired result. This method can cause strong and painful contractions and should be done, for security reasons, under close monitoring in a antenatal or labour ward. A side effect of these medications is that when the contractions are very strong this can cause distress to the baby and that would require an emergency cesarean section..

3. Artificial Rupture of Membranes (ARM)

if the cervix has 'ripened' and the baby's head is deep into the pelvis, we can perform the so called ARM. It's a medication- free method in which an appropriate, hook- like device is used to break the water. The amniotic fluid (water) contains substances that can make the cervix dilate slowly and the contractions to increase. We need to allow some hours, iIn order to see the effect of this method. If ARM, by itself, cannot have the desired effect, you may need to have your contractions augmented by the use of synthetic oxytocin (see below). A disadvantage of this method is that by breaking the water, the chance of an ascending infection increases. This might cause fetal distress and lead to an emergency cesarean section. Very rarely, the umbilical cord can be compressed or prolapse and cause fetal bradycardia (slowing of the heartbeat rate).

4. Synthetic oxytocin

During labour, a natural hormone called oxytocine is secreted by the mother and causes contractions of the womb to happen. We can augment the action of this hormone by administering synthetic oxytocin via a drip. Synthetic oxytocin drip can be administered before the onset of labour (to induce labour and contractions) or during labour to accelerate the process (labour augmentaion).

The dosage of synthetic oxytocin should increase stepwisely until we establish regular contractions. Synthetic oxytocin can cause much stronger contractions than the naturally produced oxytocin, therefore pain can also increase substantially. If pain becomes intolerable, some kind of analgesia (easing of pain) is recommended, ie epidural anesthesia, to effectively alleviate pain. When synthetic oxytocin is administered, womb contractions and the baby's heartbeat rate  should be continuously monitored. This is done by cardiotocography, an external device that provides information about contractions and fetal well- being.

What are the risks of labour induction?

Administering synthetic hormones can cause complications and side effects since the dosage is substantially higher than the naturally circulating levels. The incidence of side effects depends on the administered dosage and the type of medication used. The commones side effects include:

1. Uterine tachysystole (womb hyperstimulation): Prostaglandin and oxytocin administration cause the womb to contract. If this contractions become too frequent, without any time of relaxation between contractions, that means that the womb is stimulated excessively. This usually happens when there are more than 5 contractions every then minutes or if a contraction lasts for more than two minutes. Hyperstimulation decreases the oxygen supply to the baby resulting in heartrate dropping. Thesecomplications happen in approximately 5% of the cases.

2. Womb rupture: This is a very rare complication. It happens more often in women with a history of a previous cesarean section or womb procedure. This is why, in such circumstances, it is advisable to avoid induction of labour with administered hormones. The incidence of womb rupture is approximately 2 every 10,000 deliveries.

3. Amniotic fluid embolism: This is also a very rare complication and happen in 1 woman every 10,000 deliveries. However, we know that women that had their labour induced had a two- fold increase of the risk compared to women that were not induced.

4. Electolyte imbalance: Administration of excessive quantity of synthetic oxytocin (more than 3 lt of hypotonic solutions or administration longer than 7 hours) may lead to hyponatremia, hypotension and neonatal jaundice.

5. Prostaglandins side effects: The commonest are fever, tremor, diarrhea, vomiting.

 

How effective is labour induction?

Induction of labour usually leads to a succesful vaginal delivery, however the success rate is lower than in women that have a spontaneous labour (ie a labour that starts by itself). If there are no favorable conditions (a 'ripened' cervix, if the baby's head is not deep inside the pelvis), then the failure rate, increases substantially. Women that will have an unsuccessful induction will have to deliver by cesarean since delivery has to be completed.

Some statistics:

  • In all women that deliver for the first time (primiparas) IOL succeeds in 75% of the cases.
  • In primiparas with unfavorable cervix and a head that is not engaged (not very deep inside the pelvis), success rate drops to 60%.
  • The length of the first phase of labour (cervical dilation from 4 to 10 cm) is significantly longer in case of IOL compared to spontaneous labour (5.5 hours vs 3.8 hours).
  • In IOL, when the latent phase of labour (the stage with cervical dilation less than 4 cm) lasted up till 18 hours, the probability of a successful vaginal delivery increased significantly and without any complications for the mother or the baby.
  • In women that were induced before 41 weeks of pregnancy WITHOUT any medical reasons, the incidence of cesarean section was double (27%) that of women that were not induced (13%).
  • In women that were induced at or after 41 weeks of pregnancy, there was no difference in the rate of cesarean section. According to some research data, there was even a 22% decrease in the rate of cesarean section and also a decrease of the probabilty of stained meconium (stool in the amniotic fluid).

 

In conclusion, before choosing IOL you should be aware that, in most of the cases, you cannot cancel the whole proccess. There should be well established reasons to have an IOL. Adequate time should be allowed, so that the body manages to achieve vaginal delivery. The administration of medications should be cautious and without excessive dosages. Finally, the whole process should be done in an organised setting (antenatal or labour ward) to ensure safety for both the mother and the baby.