St George Private Hospital
Part of Ramsay Health Care

Education Updates

Weight in Pregnancy

Dr Emmanuel Karantanis, Obstetrician & Uro-gynaecologist

Until recently, weight was not considered an important determinant of pregnancy outcomes. However, the tide is turning as maternal obesity becomes linked to multiple problems for both mothers and babies. Increased BMI is associated with childhood deformities rising to 4.7% in women with a BMI >40 (Persson et al BMJ 2017;357:j2563). Other neonatal complications are also increased (preterm birth, fetal growth both too large and growth restriction, stillbirths and neonatal ICU admissions). For morbidly obese mothers, admissions to Intensive Care Increase to 4% (Lisonkova et al JAMA 2017;318:1777-86).

In 2017 my research fellow travelled to Hong Kong to observe births in Asian women, and compare them to births of Asian women at St George Hospital. We found that Asian women moving to Australia increased their babies’ birthweights, and thus significantly increased their chance of anal sphincter injuries (3rd degree tears) and caesareans at full dilatation (Bates et al IUGA Abstract 2017).

Avoiding obesity prior to pregnancy is ideal, but once pregnant, women who stay within the weight-gain recommendations and participate in exercise have lower chances of a caesarean section. Their babies have lower chances of obesity and cardiovascular disease in adult life.

The ideal gestational weight-gain depends on a woman’s pre-pregnancy Body Mass Index (BMI). The latest recommendations from the Institute of Medicine in the United States are as follows:

BMI Weight gain in kg
Less than 19 13-18
20-25 12-16
26-30 7-11
Greater than 30 5-9

Women gaining in excess of these guidelines are more likely to have babies with macrosomia and be delivered by caesarean section ( Goldstein et al JAMA; 317:2207-25). Pregnancy is a time to stay within the guidelines of weight-gain but it is also an opportunity to exercise consistently for the sake of the pregnant woman and her child. Each of us doctors who manage women planning pregnancy or who are newly pregnant, have an opportunity to influence this newly receptive audience. Assessing BMI and showing women these guidelines and counselling about weight is an early intervention which can have far reaching benefits.