Updated: Sep 26, 2019
There is no evidence that women produce babies too big for their pelvises or that big babies are more difficult to birth, particularly when women are not confined to their backs on beds. . There are no accurate methods for estimating the size of the baby, including predictions made using ultrasound and abdominal palpation (using hands to feel the baby through the abdomen). A recent study showed that women themselves were almost as accurate as ultrasound at estimating the weight (especially if this wasn’t their first baby) but neither were particularly accurate – ultrasound proved to be between 8 and 15% ‘out’. If a baby actually weighs 9 pounds, a 15% error can show an ultrasound weight of 7.6 pounds (15% too low) or 10.3 pounds (15% too high)! When a baby is larger than normal it can be more important for the woman to be able to listen to her body, to be able to move freely in labour, and to adopt positions that feel right for her. Lying on your back or sitting during labour and birth can greatly reduce a woman’s pelvic size. Upright positions and freedom of movement make the birth easier even when the baby is smaller. There are encouraging ‘big baby’ birth stories on the homebirthuk website.