Tina Gibbs

If you have listened to @themidwivescauldron back in November 2021 or follow Dr Sara Wickham, you probably know already. The Cochrane review on macrosomia (big baby) in 2016 showed that the difference in birth weight between the two groups: 1. Induced early 2.
The spontaneous onset of labour/birth was 178g. The difference is equivalent to the size of a hamster or a medium-sized pear (see Sara Wickham’s book ‘In your own time’ for more!). This should make your ‘big’ baby seem less big and scary.

However, it is your body, your baby your choice! If you fell that an induction or caesarean birth is right choice for you then that is what you should choose. Your doula or perinatal educator will support you all the way to make the right decision for you and your baby and as well supporting your choices! However, chances are you are reading this because you feel and that an induction of labour (or Caesarean birth) for a big baby is not what you want.

How can you decide whether to have an induction for a big baby or not?

The aim of the induction for big baby is to reduce the chance of ‘baby getting stuck’ (shoulder dystocia). In the majority of cases, shoulder dystocia does not result in any long term issues. Here is a printable version of the Cochrane – Pregnancy and Childbirth where you can have a look at their findings to help you make the right choice for you and your baby!

induction-for-macrosomia-printableDOWNLOAD

What are the reasons for declining and induction for a big baby?

If the size of your baby was the only reason, then you may wish to decline the induction of labour.

Reason #1 for the recommendation of induction is the assumption that big babies are at higher risk for getting stuck (shoulder dystocia). In reality, 7-15% of big babies have difficulty with the birth of their shoulders, most of these cases are handled by your midwife or obstetrician without any harmful consequences for your baby. Statistically In 1 out of every 555 babies who weigh between 8 lbs., 13 oz. and 9 lbs., 15 oz., and 1 out of every 175 babies who weigh 9 lbs., 15 oz. or greater, permanent nerve injuries due to stuck shoulders happen.

Interestingly, people with high blood sugar levels during pregnancy are at increased risk of shoulder dystocia during childbirth even when their baby is not considered big. This is because their baby’s weight can be distributed differently when their mother/parent has high blood sugars. Problems are more likely to occur if the baby’s head size is relatively small compared to the size of its shoulders and abdomen. (Kamana et al. 2015).

BUT can we really tell how big your baby is?

How accurate are the baby sizing scans or palpation? In short, both, scans and palaption are equally inaccurate/bad at predicting your baby’s size.

For the scan accuracy % check out table 3 in this article (see a copy below). It shows that the accuracy of ultrasound scan at preterm vs. term gestational age, with scan performed within three days before birth preterm (before 37 weeks) or term (37+ weeks).

Proportion of error within	±10%	±15%	±20%
Gestational age at scan:
<37 weeks	69.6	85.6	91.9
≥37 weeks	72.8	89.6	95.9

To find out more and read in more depth about induction for big babies, I recommend:

• Evidence Based Birth
• Sarah Ockwell-Smith
• Dr Rachel Reed
• Dr Sara Wickham