Diet

• A diet rich in whole grains, fruits and vegetables is important for maintaining healthy weight and a healthy body.
• In addition, a healthy diet can lower the risk of low birth weight in infants.
• Women considering a pregnancy should eat a healthy diet rich in folate and folic acid (green vegetables, beans, legumes) and take a folic acid supplement. See 'Folic acid supplements'.
• This can help prevent congenital malformations including neural tube defects, reduce premature birth and reduce the risk of preeclampsia/hypertension.

• Obesity reduces fertility and increases the risk of complications for both pregnant women and their babies.
• With increasing Body Mass Index (BMI), the risks also become higher and are significantly higher for women with a BMI over 40.

For mothers, the risks associated with a high BMI (more than 30kg/m²) include:

• thrombosis
• gestational diabetes
• high blood pressure
• pre-eclampsia

High BMI is also associated:

• with increased complications during labour including a long labour, shoulder dystocia, and the need for an emergency caesarean
• increased chance of complications during and after a caesarean delivery including anaesthetic complications
• postpartum haemorrhage

For babies, the risks of high BMI include:

• miscarriage
• preterm birth
• neural tube defects - the use of a higher dose of folate (5mg daily) in women with BMI more than or equal to 30kg/m² should be clarified with her GP
• high birth weight
• stillbirth
• higher risk of obesity and diabetes in later life

For further information see the RCOG patient leaflet ‘Being overweight during pregnancy and after birth’

Women who are underweight before pregnancy (BMI less than 18.5kg/m²) are at significantly greater risk of having premature, low birth weight babies.