“Ask Dr. HKSH” - Labour Induction

Dr. CHEUK Kwan Yiu, Queenie

Specialist in Obstetrics & Gynaecology

Q1. What is labour induction? Why is it necessary?

Labour induction is the process of artificially stimulating childbirth when a pregnant woman shows no signs of natural labour. One of the most common reasons is post-term pregnancy, which means the pregnancy extends beyond the due date. Another common reason for induction is the absence of regular uterine contractions for some time after the rupture of amniotic membrane.

Induction may also be required due to maternal health conditions, such as gestational diabetes, high blood pressure (preeclampsia), or fetal conditions, such as being too small in size for gestational age, too little or excessive amniotic fluid, abnormal blood flow in the umbilical cord, etc. Induction is also required if one has a history of adverse pregnancy outcomes, such as a sudden stoppage of fetal heartbeat during a previous pregnancy.

Q2. Is labour induction common?

Labour induction is quite common. According to data from the Hong Kong College of Obstetricians and Gynaecologists, approximately 23.4% of pregnant women undergo labour induction. This figure is comparable to those of other countries, such as over 20% in the United Kingdom, and about 31% in the United States.

Q3. Does labour induction always require a caesarean section?

Many pregnant women are deterred by induction due to a common misconception: nine out of ten inductions lead to a caesarean section. However, the data suggest otherwise.  According to the Hong Kong College of Obstetricians and Gynaecologists, the success rate of labour induction is as high as about 70-80%.

Q4. How is labour induction performed?

Once the expectant mother is admitted to the hospital, we need to confirm if the baby is in the correct position, or being “head-down”, sometimes with ultrasound if necessary.  A vaginal examination is then performed to assess the ripeness of the cervix and determine the induction method. Both mother and baby are also monitored for abnormality or sudden decrease in their heart rates. Induction is not recommended if the baby’s heart rate becomes abnormal or slows down.

Doctor will also check if the mother is experiencing regular uterine contractions, which rule out the use of medications for induction.  A proper induction method is chosen based on one’s cervical ripeness. If the cervix is not yet ripe for childbirth, it may need to be dilated by medications or mechanical methods. Once the cervix is dilated, doctor may artificially rupture the amniotic membrane to release the amniotic fluid, and then assess the level of uterine contractions. If contractions are not strong enough, oxytocin is administered intravenously to stimulate stronger contractions. There is no need for medications or mechanical induction if the cervix is already ripe for childbirth, and doctor can proceed with artificial rupturing of the amniotic membrane and intravenous injection of oxytocin to ensure adequate contractions.

While mother can have a normal diet during induction, she may have to fast when complications occur, such as abnormal heart rates or issues with the labour process. Proper pain relief is provided as needed, such as laughing gas, pain relief injections, or an epidural administered by an anaesthesiologist for pain-free delivery.

Q5. Are there risks associated with labour induction?

Labour induction does carry certain risks. The most common risk is induction failure, which may require an emergency caesarean section. Another risk is excessive uterine contractions caused by induction medications, which can lead to fetal abnormal heart rate or oxygen deprivation and also needs an emergency caesarean section. If the amniotic membrane has ruptured for too long without delivery, there is also a risk of intrauterine infection, or umbilical cord prolapse while breaking the water. Prolonged labour may also lead to excessive bleeding, vascular embolism, or even amniotic fluid embolism in rare cases.

Q6. Does labour induction cause more pain? Does it prolong labour?

First of all, we need to know about the stages of labour. Labour consists of two phases: the “Latent Phase”, which lasts from the start of labour until the cervix dilates to about 3 centimetres or "three fingers", and the “Active Phase”, in which the cervix further dilates from 3 centimetres to 10 centimetres.

Almost all inductions are performed in the Latent Phase, in which the cervix has not yet dilated. The cervix is dilated by medications or mechanical methods, which can cause pain and prolong the Latent Phase. Once the Active Phase begins, or the cervix has reached 3 centimetres, the process and pain level of induced labour are generally the same as spontaneous labour. In short, one can say labour induction takes longer time and is more painful that natural labour.