Instead, greater pre-pregnancy education and “system level changes” such as increasing taxes on sugary drinks and restrictions on the marketing of unhealthy foods should be considered.
Writing in the Medical Journal of Australia, Associate Professor Kirsten Black and Dr Adrienne Gordon note that 50% of Australian women are now overweight or obese at the start of a pregnancy.
“This has several adverse consequences for the mother, including gestational diabetes, hypertension during pregnancy, pre-eclampsia, an increased likelihood of a caesarean delivery, and an elevated risk of cardiovascular disease in future years, all of which are potentially avoidable,” they write.
“Perhaps more important, however, are the increasingly recognised intergenerational effects of maternal obesity that may be manifested during pregnancy (prematurity, stillbirth, congenital anomalies, macrosomia), during childhood (obesity) or later in adult life (increased risk of metabolic disease),” they add.
But they go on to point out that intervention to try and reduce the effects of obesity when women become pregnant may not be the ideal time.
“Evidence is growing that obesity should be tackled before pregnancy if interventions are to have any effect, but capturing those women who need to lose weight before conception is complicated by the fact that one-third of pregnancies that proceed to antenatal care are unplanned,” they state.
“There is a growing realisation by researchers, clinicians, nutritionists, consumers and other health professionals in the area of obesity that intervening during pregnancy may be too little too late,” they add.
The researchers also point out that most studies have focused on the relationship between obesity and fertility, not maternal and neonatal outcomes.
However, their paper does highlights two recent publications about large population-based cohorts demonstrating the effects that a change in pre-pregnancy weight can have on critical pregnancy outcomes.
The first report, from Canada and based on a cohort of 220,000 pregnancies, found that a 10% reduction in pre-pregnancy BMI reduced the likelihood of stillbirth by 10%.
“The second report, from the Swedish birth registry and encompassing 456 711 women, documented a dose-response association between inter-pregnancy weight gain and the risk of stillbirth. Reassuringly, neonatal mortality was reduced for overweight women who lost weight before a second pregnancy,” they state.
The authors recommended that an approach might be to educate women about the effects of obesity during their pregnancy and the post-birth period, and to advise them of programmes for reducing the risk of post-birth weight retention and therefore of obesity during later pregnancies.
“Women should be aware of the increased risks that obesity poses during and after their pregnancy and be supported to make and maintain diet and lifestyle changes to improve their health,” said the authors.
“This approach will require hospitals and health services to take a more long-term perspective of pregnancy and the post-birth period, as well as government investment in these public health strategies.”
The paper also states that more should be done to promote preferences for healthy foods “including increasing taxes on beverages with a high sugar content and controlling the marketing of unhealthy foods.”
“There is some evidence that these strategies can reduce the consumption of less healthy products and lead to re-formulations that reduce their sugar, fat or salt content, but no studies have reported a population impact on obesity,” they conclude, pointing out that If current trends persist, about 80% of all Australian adults and one-third of Australian children will be overweight or obese by 2025.