Body Mass Index or BMI is a straight-forward calculation taking into account purely the height and weight of a person; BMI does not take into account the overall health status or stature of the person, and in terms of a pregnant mother, it does not take into account previous pregnancies/labours, if any. Before the implementation of the BMI calculation, maternity staff were more interested in a woman’s weight gain in pregnancy rather than the woman’s size in general.

Women are being denied the option to have a homebirth based on this calculation. The NICE guidelines recommend that a woman with a BMI>35 should be in an obstetric-led unit for labour and delivery, while women with a BMI between 30 and 34 should be assessed on an individual basis for determination of where they should be ‘allowed’ to labour. However, the choice is ultimately up to the mother-to-be where she wants to give birth to her baby.

Mothers-to-be with a high BMI (BMI> 30 for the purposes of this information) may be at a higher risk of developing gestational diabetes and hypertension during pregnancy, but there has been no solid evidence that the size of a woman has a bearing on the outcome of the birth. In fact, a study published in 2011 summarises that women with high BMI are having their labours managed differently and choices restricted, so that there are higher intervention and caesarean section rates without a real need for these medicalised procedures – a self fulfilling prophesy.

A study published in September 2013 suggested that otherwise low-risk obese women, who have previously given birth, may have fewer complications than previously thought. The study concluded “Otherwise healthy multiparous obese women may have lower intrapartum risks than previously appreciated. BMI should be considered in conjunction with parity when assessing the potential risks associated with birth in non-obstetric unit settings.”

Women with raised BMI giving birth to a second or subsequent baby were found to be at LOWER risk of obstetric complications than first time mums with normal BMI. See here for the Royal College of Obstetricians & Gynaecologists response to the study.

Midwives or consultants may express concerns about shoulder dystocia due to the woman growing a large baby but as with any other ‘big baby’, the best positions to adopt for birthing are those which allow the woman to move freely and instinctively to allow the baby to move into the best position for birth.
Indeed, a birthing pool may be one of the best options for a woman with a high BMI but as with any labour, active birthing positions can be useful, including lunges or the use of a birthing ball, but the fact remains that frequent position changes are beneficial regardless of the mother-to-be’s size. If you have a very high BMI, your midwives may express concern regarding helping you to move position, particularly in a pool and especially in the event of an emergency. You may want to consider having someone who is able to assist with this or perhaps think about additional birth partners who could help out too.

Recommended reading:

Effect of Body Mass Index on pregnancy outcomes in nulliparous women delivering singleton babies.

Science & Sensibility – Maternal Obesity from All Sides

AIMS – Researching Obesity

The Well-Rounded Mama

Big Birthas Blog

Plus Size Birth