Editorials

Maternal obesity and heart disease in the offspring

BMJ 2013; 347 doi: http://dx.doi.org/10.1136/bmj.f4960 (Published 13 August 2013) Cite this as: BMJ 2013;347:f4960
  1. Pam Factor-Litvak, associate professor of epidemiology
  1. 1Department of Epidemiology, Mailman School of Public Health, Columbia University, New York, NY 10032, USA
  1. prf1{at}cumc.columbia.edu

Interventions may need to begin before pregnancy

The prevalence of overweight and obesity in women of childbearing age and in pregnant women has steadily increased over the past 20 years.1 2 Maternal obesity is associated with a variety of adverse outcomes for the mother, such as increased mortality, pre-eclampsia, and gestational diabetes. It is also associated with adverse outcomes for the child at birth (such as large for gestational age babies and fetal distress) and in later life (such as increased risk of later obesity, metabolic disorders including insulin resistance and dyslipidemia, hypertension, asthma, and behavioral problems).3 The linked paper by Reynolds and colleagues (doi:10.1136/bmj.f4539) is the first to describe associations between maternal obesity and risk of cardiovascular morbidity and mortality in mid-life.4

What are the possible explanations for such associations? In 1992, Barker first proposed the fetal origins hypothesis, which, briefly stated, posits that an adverse intrauterine environment is associated with lifelong consequences.5 In its first application, low birth weight as a result of maternal undernutrition was associated with cardiovascular risk factors such as raised blood pressure in the adult offspring.6 This was probably due to a mismatch between programming for a “thrifty phenotype” and overnutrition in the postpartum period.

As with maternal undernutrition, maternal overnutrition and obesity are associated with definite changes in the intrauterine milieu, such as increased circulating cytokines, glucose concentrations, and lipids, as well as increased insulin resistance—all of which may lead to an increased supply of nutrients to the developing fetus.3 Among the mechanisms of fetal adaptation to overnutrition are epigenetic changes in response to increased fetal exposure to glucose, lipids, and inflammatory cytokines.3 Thus, offspring may experience permanent or transient changes in metabolic programming, leading to inappropriate appetite regulation and behavioral problems associated with obesity in adult life.

Data supporting such associations are observational. The Nurses’ Health Study, for example, found a J shaped association between birth weight and later obesity7; this finding was replicated in the Health Professionals’ Follow-up study.8 Two systematic reviews also support this finding.9 10

While intriguing, Reynolds and colleagues’ study leaves at least two questions unanswered. Firstly, what is the role of the early postnatal environment? A recent study from the 1958 British birth cohort found associations between parental body mass index and risk factors for cardiovascular disease among the offspring during mid-life. In that study, parental height and weight were measured when the offspring were 11 years of age.11 Associations remained after adjustment for offspring lifestyle and socioeconomic factors but were reduced after adjustment for adult adiposity. These finding suggest intergenerational transmission of obesity, perhaps owing to postnatal circumstances reflecting parental and childhood obesity.

Secondly, what is the role of parental obesity? In the 1958 British birth cohort, results were not stronger for maternal obesity than for paternal obesity. Results were also similar when maternal prepregnancy weight was substituted for maternal body mass index at offspring age 11, suggesting a role for the postnatal environment.

If Reynolds and colleagues’ findings are true, what are the implications? The US Institute of Medicine guidelines, adopted in 2009, recommend weight gains of 15 lb (6.8 kg) to 25 lb and 11-20 lb for overweight and obese pregnant women, respectively, with no more than 0.6-0.5 lb weight gain per week in the second and third trimesters. These guidelines were adopted by the American College of Obstetricians and Gynecologists in 2013,12 with the caveat that appropriate diet and exercise be discussed throughout pregnancy. The goals of such management are to balance the risks of fetal growth, obstetric complications, and maternal complications. However, the results of studies of maternal obesity and offspring outcomes suggest that interventions should begin before pregnancy.

Notes

Cite this as: BMJ 2013;347:f4960

Footnotes

  • Research, doi:10.1136/bmj.f4539
  • Competing interests: I have read and understood the BMJ group policy on declaration of interests and declare the following interests: None.

  • Provenance and peer review: Commissioned; not externally peer reviewed.

References