“Ask Dr. HKSH” - Foley Bulb Induction (Balloon Catheter Induction)

Dr. CHEUK Kwan Yiu, Queenie

Specialist in Obstetrics & Gynaecology

Q1. What are the current methods for labour induction?

The method mostly depends on cervical ripeness. How is it assessed? A scoring system called “The Modified Bishop Score” is used to evaluate cervical softness, dilation, length, position, and the position of the fetal head. If the Bishop Score is below 6, the cervix is considered immature; if the Bishop Score is above 6, the cervix is considered mature.

How can we do to dilate the cervix if it is immature? The most common method is medications. Two types of medication are often used, and among them prostaglandin is most frequently prescribed by obstetricians in Hong Kong. It comes in different types and potencies, and is mostly inserted vaginally to soften and dilate the cervix while stimulating uterine contractions. The other one is misoprostol, which is less commonly used by obstetricians in Hong Kong. It can be inserted vaginally or taken orally, with the latter being safer. While misoprostol can soften and dilate the cervix, intense uterine contractions are more likely to occur, making it a less preferred option among local obstetricians.

Physical methods have become more common in recent years, as the cervix can be mechanically opened and dilated with a balloon. It also stimulates the production of natural oxytocin during the process, promoting cervical softening, dilation, and also uterine contractions.

Q2. How is balloon catheter induction performed? Is anaesthesia required?

The insertion of balloon catheter does not require anaesthesia. To properly insert a balloon catheter, one is positioned with legs spread, just like having a gynecological examination. Where should the catheter be inserted? It needs to be placed between the internal cervix and the amniotic membrane. After insertion, doctor will fill the balloon with saline solution. One can resume normal diets afterwards, and is free to move some time after the balloon is left in place. After a certain period of time, doctor will remove the balloon to check if the cervix has dilated. If it has dilated, doctor will rupture the amniotic membrane and proceed with induction.

Q3. How effective is balloon catheter induction compared to traditional induction methods? What are its advantages?

According to the past data, pharmacological and physical methods are equally effective (with roughly similar success rates) and have almost the same incidences of emergency caesarean section due to fetal heart rate issues. Yet balloon catheter induction does have one advantage over medications: it is less likely to cause excessive uterine contractions that could affect fetal heart rates.   

Q4. Who are suitable for balloon catheter induction?

According to current medical recommendations, balloon catheter induction is more suitable for pregnant women who have high-risk factors, may experience excessive uterine contractions, or want to attempt natural delivery despite previous caesarean section and undilated cervix.  The latter group should consult a specialist in obstetrics and gynaecology, as the recommendations differ for each individual case.Gynaecology