Told You're Having a Big Baby? Here's What You Actually Need to Know
When measuring a ‘big baby’ ultrasounds are right half of the time and wrong half of the time. 1 in 3 US women are told they have a big baby to birth. But when born only 1 in 10 are actually born big.
Ultrasound results are usually between 15% above or below your baby’s actual weight. This means that if your baby’s weight was 8lbs/3.6kg the estimation via ultrasound could have been anywhere between 6lbs 13oz/2.8kg and 9lbs 3oz/4.2kg. Or, if we take the current cut off point for a suspected big baby which is 8lbs 8oz/4kg the estimated ultrasound could range from 7lbs 5oz/3.4kg to 10lbs 4oz/4.6kg
It is fair to say that the only guaranteed way of knowing how much your baby will weigh is to weigh them after they’ve been born!
The fear with a large baby (macrosomia) is that once their head has been born their shoulders may get stuck which is referred to as shoulder dystocia, but this is a very rare occurrence and can be heavily influenced by the position a woman is in when birthing (see Ina May Gaskin’s Ted Talk on the subject) and while 7-15% of big babies do have difficulty with the birth of their shoulders (shoulder dystocia), most of these cases are handled by the care provider without any harmful consequences for the baby or mother. It is also really helpful to keep in mind that many cases of shoulder dystocia occur in babies that are of an average or smaller than average size.
It is important to remember that historically women have been forced to birth lying down on their backs, potentially with their feet up in stirrups (lithotomy position). When a woman births standing up, in an upright supported position or on all fours her pelvis has the ability to expand up to 30%! Therefore if we do have signs of a bigger baby then induction of labour, which generally involves a women staying on her bed to give birth and usually with the accompaniment of an epidural, is not always the most sensible of options.
The NICE guidelines on the subject of Induction of Labour for a big baby are clear, they state: ‘In the absence of any other indications, induction of labour should not be carried out simply because a healthcare professional suspects a baby is large for gestational age (macrosomic).’ It would be helpful for hospital trusts to remember this.
The bottom line is that it is your decision as the birthing mother. That decision needs to be made with both evidence and your gut feeling. Evidence on the subject can come from Dr Sara Wickham, Rachel Reed, AIMS or Evidence Based Birth among many places. Then when you have a good overview of the subject you can choose the path which is right for you. Do not let yourself get swept up with the fear of early induction or the idea that you may as well just choose an elective caesarean to start with. Your body, if healthy and well and not affected by gestational diabetes, will not create a baby too big for you to birth. And, you know, even if it did? Well, then your gorgeously chunky baby will not descend and after labouring for some time you could always elect for a caesarean at that point. Do remember that labour is actually really good for your baby as it helps to prepare them for life outside of you.
Most importantly, please remember, there will be big babies…there will be small babies. Just as there are big adults and there are small adults. And there always will be.
And lastly, women can birth big babies just fine 💪 , just ask around or search social media. Women are powerful and built to birth their babies! We just need more trust, more support, decent evidence and perhaps less fear-mongering from society.