Can we talk about 'Big Babies'?

This situation has happened countless times in my classes:

Mama says (with a very concerned facial expression) "my consultant says I'm having a big baby and I might need a section". One of the most disempowering lines a pregnant woman can hear, in my view, when they had never previously considered anything but a straight forward vaginal birth. Basically the doctor is saying, 'love, your body has grown a baby that's too big for you and you won't be capable of birthing it yourself'. I find it very frustrating, as so many times the comments are not based on facts. What doctors tend to be concerned about is that the baby gets 'too big for the woman's body' or may get 'stuck' in the birth canal, leading to a traumatic birth for both the baby and the mother. A valid concern certainly. 

But looking at the facts, the actual evidence does not support the theory. So who exactly is 'at risk' of having a 'big baby'? There are some health conditions and your own birth history which can place you at an increased risk. 

The main three are:

  1. Having diabetes is a concern as baby can get bigger than average due to potential uncontrolled sugar levels which can cross the placenta, causing baby to  respond with increased insulin, in turn stimulating growth.
  2. An overweight mother is another obvious risk factor. 
  3. Finally, if you have already had a big baby, you are more likely to have subsequent large babies. Again, this is not always the case, but the trend is there. 

There is a condition called shoulder dystocia which can be of concern, which is 'when the baby’s head has been born but one of the shoulders becomes stuck behind the mother’s pubic bone, delaying the birth of the baby’s body'*. Obviously nobody wants this. However, if you look at the statistics, the rate of recorded shoulder dystocia is tiny. 'Shoulder dystocia occurs in about one in 150 (0.7%) vaginal births'*. Shoulder dystocia is more likely to occur if you:

  • Have had it before
  • Have diabetes
  • BMI is 30 or more
  • Labour is induced
  • Have an assisted vaginal birth (forceps / ventouse)

Shoulder dystocia is also more likely with large babies but there is no difficulty delivering the shoulders in the majority of babies over 4.5 kg (10 lb)*. What I found really interesting in my research is that half of all instances of shoulder dystocia occur in babies weighing less than 4 kg (about 9 lb).* So for (at least) half of these cases, it's the baby's position that is the cause of the shoulder dystocia and not the size of the baby. I've written and spoken extensively about how you can help get your baby in a good birthing position.  

To me, all this rhetoric serves to do is to create fear and disempowerment, and starts to fill the mama-to-be's head with lots of doubt. 'Can I give birth to a big baby'...'Is my baby going to be a giant'?!

Yes some babies are large (over 10lbs is typically classed as a 'large baby'), and now you know the risk factors you can do as much as you can to not put yourself in this group. But out of all the ladies who have been in my classes over the past 8 years, I can only think of 2 who have had 10 pound babies. And don't forget, in Ireland the average size baby is approximately 7lbs 7oz, and that really hasn't fluctuated much in years. 

So let's look at more facts! Most, if not all doctors or sonographers will measure the weight of the baby using an ultrasound. Ultrasound is not a very reliable estimation of baby's weight near to the end of the pregnancy.

So how does ultrasound actually work? It uses volume to calculate the baby's weight. It takes measurements of the head, the waist circumference and a few bones, and then comes up with an estimate. But obviously it cannot measure the density or weight of the bones themselves. 

In general, an ultrasound's predicted accuracy is typically 10-15% and even up to 20% off! Let's look at examples of that. Say for example at your 36 week appointment, the doctor starts to make faces, saying 'ok so baby is very large. They are currently measuring 7 lbs, so you are probably going to have at least a 9lb baby'. You start panicking. But pause for a moment and look at what those percentages could actually mean.

In this scenario above, a 10% inaccuracy could mean a baby of an estimated final weight of 8lbs 2oz; 15% could mean 7lbs 10oz; 20% could result in a baby of 7lbs 3oz. So yeh, that's why I often say take what they say with a pinch of salt, unless you are in the very small group of high risk pregnancies. Most of the time it is horse manure!! I try to encourage my pregnant ladies to focus on their own health and wellbeing, and stop focusing on potential stumbling blocks and negativity.

I remember one of my lovely ladies came up to me at the end of class in tears one evening. Her consultant had warned her she was having a monster-sized baby. She cried so much for the remaining weeks of her pregnancy and was really quite terrified. It had a very negative impact on her and she felt she could not enjoy her pregnancy. Needless to say, her perfect little baby was born a few weeks later weighing 8lbs even! I have so many stories I could tell you of needless early inductions, needless C-section births and also a ton of terrified, fear-filled heavily pregnant women. It drives me bloody nuts. 

The recommendations from the American Congress of Obstetricians and Gynaecologists are clear. ACOG says 'ultrasound is no better than a provider’s exam in estimating fetal weight, suspected macrosomia (large baby) should not be an indication for induction of labor, and planned C-sections shouldn’t be performed unless the estimated fetal weight is 10 pounds or more in diabetic women or 11 pounds or more in other women'.

Personally, I gave birth naturally to my three boys who were all in and around 9lbs, without any form of trauma (8lb 13oz; 8lbs 10oz; 9lbs 2oz). So giving birth to a 'bigger' baby is 100% possible and entirely manageable. 

If you fit into the description of risk factors above, I'd strongly recommend you start doing some research and discussing your situation with your doctor.

I would be honoured if I could support you in your pregnancy, by joining me in The Club, our amazing Monthly Membership. You will be able to educate yourself, stay fit and healthy in body and mind.  For more information, have a read here.

In conclusion, I've given you all the facts and also my own anecdotal and personal experiences. Unless a doctor can open you up during your pregnancy, take the baby out, pop it onto a scales and place it carefully back inside you, they really have no accurate way of measuring the baby's weight, regardless of how confident they sound. Keep healthy, keep your expected weight gain in the recommended guidelines, and believe in yourself, work on your posture and positioning and educate yourself all during your pregnancy and you'll have your kick a*s birth ;-)

* Royal Collage of Obstetricians and Gynaecologists, UK.

Helen Plass is a Pre & Postnatal Fitness Specialist, and Yoga Instructor, working with women and their birthing partners to achieve a comfortable, healthy & happy journey into Pregnancy, birth and Motherhood. Check out The Club @ NurtureMamas, the fabulous Monthly Online Membership club preparing you for an incredible Pregnancy & Birth journey. She is a mother of three boys, all birthed naturally, and is known for her very practical & non-judgmental approach to pregnancy and the crazy times of motherhood. Check out all her communication at NurtureMamas.com, and if you are in Ireland, her local business MumandBaby.ie