With the rise of the obesity epidemic worldwide, the prevalence of obesity and overweight among pregnant mothers is also on the rise. The prevalence of type 2 diabetes or gestational diabetes as a parallel is also on the rise.

The Confidential Enquiry into Maternal and Child Health (CEMACH) found that 27% of pregnant women with pre-existing diabetes had type 2 diabetes while 87.5% of diabetes in pregnancy is due to gestational diabetes.

Women who are diagnosed with gestational diabetes further have a 30% risk of developing full blown type 2 diabetes during their lifetime compared to a 10% risk in general population.

Obesity and overweight gain during pregnancy is one of the most important risk factors for developing diabetes. The CEMACH found that women with diabetes were more likely to be older, black, Asian or other ethnic minority group, on multiple pregnancies, living in socially deprived areas and overweight. These patients are more likely to have BMI >30 kg/m2 with 62% of those with type 2 diabetes and 15% with type 1 diabetes being obese.

Overweight and obesity are increasing dramatically in pregnancy. A 2010 study by Heslehurst et al found that obesity in the first trimester has more than doubled increasing from 7.6% to 15.6% in a 19-year period. Despite these rising numbers the recommendations for weight management in pregnancy are unclear.

NICE (2010) recommends:-

• A healthy weight should be targeted before conception
• Dieting and fad diets should be completely avoided during pregnancy

USA’s Institute of Medicine (2009) recommends pregnant women with a BMI more than 29.9 kg/m2 should limit weight gain to 5–9 kg. The Centre for Maternal and Child Enquiries and the Royal College of Obstetricians and Gynaecologists (CMACE/RCOG) joint guidelines (2010) adds that all women with a body mass index over 30 must be screened for glucose tolerance. CMACE/RCOG guidelines specify diet plans for obese and overweight pregnant women.

Weight loss before conception

Weight loss is advised before conception and after delivery rather than during pregnancy. Weight loss during pregnancy may lead to poor results as well as complications like hyperemesis gravidarium.

Daily energy intakes in pregnancy of 600–1500 kcal were associated with complications like premature labour, stillbirth and neural tube defects in the first half of pregnancy. Restricted energy intake during the second half of pregnancy was associated with low birth weight of the baby.

However, some studies have shown that women who were morbidly obese with BMI of over 40 and lost weight throughout pregnancy had a reduced risk of caesarean section by 24% and large for gestational age births (large babies – a common complication of gestational diabetes) by 11.2%, compared with women in the same BMI class who gained a modest amount of weight during pregnancy.

Another study on pregnant women with BMI over 30 showed that where weight gain was restricted to ≤6 kg, all babies delivered were healthy.

Calorie requirement for pregnant women

The estimated average requirement (EAR) for energy in pregnancy is an additional 200 kcal per day in the third trimester according to the Committee on Medical Aspects of Food Policy, 1991. This is appropriate for women who are currently consuming the recommended EAR of 1900 kcal per day (for non-pregnant women). Usually women over BMI of 30 are consuming the recommended amount or more and do not need extra calories.

Dietary advice in pregnancy should focus on healthy eating with a balanced diet. Meals should be balanced and regular on time. Women are advised to avoid high sugar food and drinks, sugary snacks such as chocolate, sweets, cakes, biscuits etc. A low sugar diet is often a reduced calorie diet and may prevent excessive weight gain in pregnancy.