Tackling childhood obesity at its maternal roots

Abstract

Among the effects of the worldwide obesity epidemic, the consequences for pregnant women and their offspring are among the most serious. Obesity in pregnancy increases the risk of several adverse maternal outcomes, including gestational diabetes, hypertensive disorders, caesarean section, preterm birth, and postpartum haemorrhage. More importantly, maternal obesity has negative implications for the offspring, both perinatally and later in life—including an increased risk of obesity, heart disease, and premature mortality.In the USA, more than half of pregnant women are overweight or obese; prevalence of maternal obesity in other high-income countries is similarly high, and increasing quickly in many low-income and middle-income countries. There is now little doubt that this trend has contributed to the prevalence of childhood obesity, a problem WHO considers to be one of the most serious public health issues of the 21st century, which has been steadily rising in the past two decades.In view of this cycle of obesity begetting obesity, there is an urgent need to assess whether interventions in high-risk pregnant women, which typically aim to reduce weight or improve glycaemia, can reduce the risk of adverse outcomes in offspring. This issue features two Articles that shed light on this question. Results of two randomised controlled trials assessing different approaches in obese pregnant women (BMI 30 kg/m2), starting roughly from the beginning of the second trimester, suggest that the interventions tested are not sufficient to improve maternal or infant outcomes, at least in the short term. Lucilla Poston and colleagues report that a behavioural intervention did not affect either of the primary outcomes tested: incidence of gestational diabetes or large-for-gestational-age infants. Similarly, Carolyn Chiswick and colleagues found that treatment of obese pregnant women with normal glucose tolerance with metformin had no effect on the birthweight of infants in the study. With some exceptions, these results are mostly in line with those of other studies that tested similar interventions in different settings.Why did these carefully planned interventions, which have been shown to be beneficial for other outcomes in non-pregnant adults, have little or no effect in these studies? Although promotion of a healthy lifestyle in pregnant women should continue to be encouraged, some would argue that interventions targeting pregnant women are too little, too late. There is increasing speculation that obesity results in indelible epigenetic changes in placental and fetal genes that programme the developing fetus towards obesity, well before lifestyle interventions are typically initiated. Intriguingly, the investigators of a third report in this issue used historical data from the Ukraine famine of 1932–33 to explore the paradoxical hypothesis that undernutrition can also predispose offspring to metabolic disease. The results suggest that the first trimester is the crucial time window during which negative effects on the developing infant take effect: people born to mothers exposed to extreme famine during the first 3 months of pregnancy had a higher risk of type 2 diabetes later in life, an effect that was less pronounced in regions with less severe famine.These and other findings support a move to focus more effort and funding on lifestyle interventions as a part of pre-pregnancy counselling in the roughly 50% of women whose pregnancies are planned. In view of the high rate of unplanned pregnancy, especially in young adults, advice on the importance of a healthy pre-pregnancy BMI could be broadly initiated as early as adolescence, ideally as part of public health initiatives to improve physical activity levels and reduce obesity in all young people. Additionally, some aspects of pre-conception or antenatal guidance might need to be specifically tailored for women of different ethnic origins because metabolic risk factors such as high BMI might require ethnic-specific cutoffs. For example, Diane Farrar and colleagues report in this issue that different criteria to diagnose gestational diabetes should be used in south Asian versus white British women, based on the results of their study of the Born in Bradford cohort. Importantly, the effectiveness of ethnic-specific approaches will require that information is provided in different languages and that care is delivered in a culturally appropriate manner.The most effective means to improve outcomes for mothers and their offspring will be the implementation of lifestyle and nutritional counselling—and possibly pharmacological treatment—before, during, and after pregnancy. Such an approach will contribute to an effective fight against childhood obesity, before children are even part of the equation. Among the effects of the worldwide obesity epidemic, the consequences for pregnant women and their offspring are among the most serious. Obesity in pregnancy increases the risk of several adverse maternal outcomes, including gestational diabetes, hypertensive disorders, caesarean section, preterm birth, and postpartum haemorrhage. More importantly, maternal obesity has negative implications for the offspring, both perinatally and later in life—including an increased risk of obesity, heart disease, and premature mortality. In the USA, more than half of pregnant women are overweight or obese; prevalence of maternal obesity in other high-income countries is similarly high, and increasing quickly in many low-income and middle-income countries. There is now little doubt that this trend has contributed to the prevalence of childhood obesity, a problem WHO considers to be one of the most serious public health issues of the 21st century, which has been steadily rising in the past two decades. In view of this cycle of obesity begetting obesity, there is an urgent need to assess whether interventions in high-risk pregnant women, which typically aim to reduce weight or improve glycaemia, can reduce the risk of adverse outcomes in offspring. This issue features two Articles that shed light on this question. Results of two randomised controlled trials assessing different approaches in obese pregnant women (BMI 30 kg/m2), starting roughly from the beginning of the second trimester, suggest that the interventions tested are not sufficient to improve maternal or infant outcomes, at least in the short term. Lucilla Poston and colleagues report that a behavioural intervention did not affect either of the primary outcomes tested: incidence of gestational diabetes or large-for-gestational-age infants. Similarly, Carolyn Chiswick and colleagues found that treatment of obese pregnant women with normal glucose tolerance with metformin had no effect on the birthweight of infants in the study. With some exceptions, these results are mostly in line with those of other studies that tested similar interventions in different settings. Why did these carefully planned interventions, which have been shown to be beneficial for other outcomes in non-pregnant adults, have little or no effect in these studies? Although promotion of a healthy lifestyle in pregnant women should continue to be encouraged, some would argue that interventions targeting pregnant women are too little, too late. There is increasing speculation that obesity results in indelible epigenetic changes in placental and fetal genes that programme the developing fetus towards obesity, well before lifestyle interventions are typically initiated. Intriguingly, the investigators of a third report in this issue used historical data from the Ukraine famine of 1932–33 to explore the paradoxical hypothesis that undernutrition can also predispose offspring to metabolic disease. The results suggest that the first trimester is the crucial time window during which negative effects on the developing infant take effect: people born to mothers exposed to extreme famine during the first 3 months of pregnancy had a higher risk of type 2 diabetes later in life, an effect that was less pronounced in regions with less severe famine. These and other findings support a move to focus more effort and funding on lifestyle interventions as a part of pre-pregnancy counselling in the roughly 50% of women whose pregnancies are planned. In view of the high rate of unplanned pregnancy, especially in young adults, advice on the importance of a healthy pre-pregnancy BMI could be broadly initiated as early as adolescence, ideally as part of public health initiatives to improve physical activity levels and reduce obesity in all young people. Additionally, some aspects of pre-conception or antenatal guidance might need to be specifically tailored for women of different ethnic origins because metabolic risk factors such as high BMI might require ethnic-specific cutoffs. For example, Diane Farrar and colleagues report in this issue that different criteria to diagnose gestational diabetes should be used in south Asian versus white British women, based on the results of their study of the Born in Bradford cohort. Importantly, the effectiveness of ethnic-specific approaches will require that information is provided in different languages and that care is delivered in a culturally appropriate manner. The most effective means to improve outcomes for mothers and their offspring will be the implementation of lifestyle and nutritional counselling—and possibly pharmacological treatment—before, during, and after pregnancy. Such an approach will contribute to an effective fight against childhood obesity, before children are even part of the equation. Effect of a behavioural intervention in obese pregnant women (the UPBEAT study): a multicentre, randomised controlled trialA behavioural intervention addressing diet and physical activity in women with obesity during pregnancy is not adequate to prevent gestational diabetes, or to reduce the incidence of large-for-gestational-age infants. Full-Text PDF Open AccessEffect of metformin on maternal and fetal outcomes in obese pregnant women (EMPOWaR): a randomised, double-blind, placebo-controlled trialMetformin has no significant effect on birthweight percentile in obese pregnant women. Further follow-up of babies born to mothers in the EMPOWaR study will identify longer-term outcomes of metformin in this population; in the meantime, metformin should not be used to improve pregnancy outcomes in obese women without diabetes. Full-Text PDF Open AccessAssociation between type 2 diabetes and prenatal exposure to the Ukraine famine of 1932–33: a retrospective cohort studyThese results show a dose–response relation between famine severity during prenatal development and odds of type 2 diabetes in later life. Our findings suggest that early gestation is a critical time window of development; therefore, further studies of biological mechanisms should include this period. Full-Text PDF Association between hyperglycaemia and adverse perinatal outcomes in south Asian and white British women: analysis of data from the Born in Bradford cohortOur data support the use of lower fasting and post-load glucose thresholds to diagnose gestational diabetes in south Asian than white British women. They also suggest that diagnostic criteria for gestational diabetes recommended by UK NICE might underestimate the prevalence of gestational diabetes compared with our criteria or those recommended by the International Association of Diabetes and Pregnancy Study Groups and WHO, especially in south Asian women. Full-Text PDF Open Access