In Europe the World Health Organisation estimate that more than 50% of men and women are overweight or obese and 23% of women are obese.
In a pregnant woman obesity raises her chances of gestational diabetes and pre-eclampsia. She is also more likely to get metabolic syndrome and type two diabetes later in life. The resulting children are more likely to come to harm in utero and at birth and also more likely to become fat children. They are then more likely to develop higher blood pressure and excess weight in early adulthood.
Despite the push to improve the outcome for the babies in utero, lifestyle changes and medical interventions have largely proved unsuccessful.
Women with a BMI over 25 find it more difficult to conceive in the first place and then are more likely to miscarry compared to their slimmer sisters. The miscarriage rate is 1.67. Congenital abnormalities become more common.
The placenta responds to maternal insulin levels. In normal weight women they become 40-50% less sensitive to insulin but this bounces back within days of delivery. Obese women show greater decreases in insulin sensitivity, this affects lipid and amino acid metabolism. African Americans and Southern Asians get these changes at lower body masses than Europeans.
Obese women are more likely to go into labour early. They also may need to be delivered early. They have a higher rate of failed trial of labour, caesarean sections and endometritis and have five times the risk of neonatal injury.
Anaesthetic complications are more common. The Royal College of Obstetrics and Gynaecology recommend that women with a BMI over 40 see an obstetric anaesthetist before going into labour. Epidural failure is more common. The woman may have lower blood pressure and respiratory problems and the baby may have more heart rate decelerations in labour.
Broad spectrum antibiotics are recommended for all caesarean sections. Despite this, overweight women get more post- operative infections. The wounds are also more likely to come apart.
Obese pregnant women are obviously at even more risk.
Babies of obese mothers are usually fatter at birth compared to other babies. Obese mums tend to put on more weight than average during the pregnancy and then find it even harder to lose weight after delivery.
Recent randomised controlled trial have shown that interventions started after pregnancy have little or no effect. These include increasing the mum’s physical activity and cutting the dietary glycaemic load. These things reduced the weight gained in pregnancy a little but did not affect adverse pregnancy outcomes and the birth of fat babies. Thus there is now a bigger push to intervene before pregnancy.
Currently between ten and twenty percent of obese women lose weight between pregnancies. This has been found to reduce weight gain in the next pregnancy and also the risk of pre-eclampsia. Supervised intensive lifestyle interventions can be done, work and are safe, even in breast feeding mothers. Pre-pregnancy classes to get women fit for pregnancy would help improve the outcome for the babies of the future. The metabolic environment, a mixture of inflammation, insulin resistance, lipotoxicity, and hyperinsulinemia, can then be optimised prior to conception. After this, it is really too late.
Adapted from Obesity and Pregnancy. Patrick M Catalano and Kartik Shankar from Cleveland Ohio and Little Rock Arkansas Universities. BMJ 18 February 2017 BMJ 2017;356;j1