Perspectives
Metabolic diseases
Volume 205 - Issue 4

Obesity before pregnancy: new evidence and future strategies

Authors:  Kirsten I Black and Adrienne Gordon

Med J Aust 2016; 205 (4): 152-154. || doi: 10.5694/mja16.00469
Published online: 15 August 2016
Pre-conception weight control is important for both mother and child — and for Australia
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Pre-conception weight control is important for both mother and child — and for Australia

The world is getting fatter. Between 1975 and 2014 we transitioned from a planet with a higher prevalence of malnourished individuals to one in which there are more obese than underweight people.1 The mean body mass index (BMI) of Australian women rose during this period from 23.4 kg/m2 to 26.8 kg/m2, so that 50% 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,2,3 all of which are potentially avoidable. 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).3,4

While pregnancy may be an opportune time to intervene, as women are often more motivated to change their behaviour during this period,5 it may not be the ideal point for trying to reduce the effects of obesity. Trials of antenatal interventions undertaken with the aim of limiting gestational weight gain by obese women have had only limited success in improving important perinatal outcomes, such as rates of caesarean delivery, large for gestational age (LGA) babies, neonatal birthweight, and macrosomia.6,7 The largest randomised control trial of limiting gestational weight gain has been the Australian LIMIT trial, which assessed a lifestyle intervention (diet and physical activity) in 2212 overweight and obese pregnant women.6 The intervention, despite appropriate statistical power, did not achieve a reduction in the primary outcome (LGA infants: birthweight above the 90th percentile), although it did find a statistically significant reduction in the secondary outcome of macrosomia (birth weight more than 4 kg) in the intervention arm (15% v 19% in the control arm; P = 0.04). There was no significant difference in maternal gestational weight gain (intervention arm, 9.39 kg [SD, 5.74]; control arm, 9.44 kg [SD, 5.77]; P = 0.89). The findings of the UPBEAT trial,7 a complex intervention involving face-to-face sessions during which information on healthy food, exercise programs and strategies for encouraging behavioural change were provided, similarly found no impact on the primary outcomes of gestational diabetes and LGA babies.

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.8 Targeting obesity before pregnancy potentially offers a greater benefit. Two recent publications about large population-based cohorts highlight the particular 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 225 000 pregnancies, found that a 10% reduction in pre-pregnancy BMI reduced the likelihood of stillbirth by 10%.9 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 (relative risk [RR] associated with a BMI increase ≥ 4 kg/m2 [v a change of –1 to < 1 kg/m2], 1.55; 95% CI, 1.23–1.96).10 Reassuringly, neonatal mortality was reduced for overweight women who lost weight before a second pregnancy (RR associated with a BMI reduction > 2 kg/m2, 0.49; 95% CI, 0.27–0.88). A recent Cochrane review of targeted pre-conception interventions in overweight or obese women, however, found no controlled trials relevant to this aim, and called urgently for research in this area.11

Laboratory research has indicated that the risk of intergenerational obesity is not limited to maternal obesity, with recent work finding that, in rats, a high fat diet for either parent renders it more likely that their offspring will develop obesity and diabetes.12 If these results can be transferred to humans, they suggest that epigenetic factors account for some of the risk of offspring becoming obese, with the consequence that attempts to reduce rates of childhood obesity are unlikely to be wholly successful unless significant attention is shifted to parental obesity.

Pre-conception care involves providing health care to women of reproductive age and their partners that optimises their physical, social and emotional wellbeing prior to conception, with the aim of improving health-related outcomes for women and their children. A United States epidemiologic study that used nationally representative data to assess the potential beneficial effects on birth outcomes of universal pre-conception care for women with pre-gestational diabetes estimated that it might avert 8397 (90% prediction interval [PI], 5252–11 449) pre-term deliveries, 3725 (90% PI, 3259–4126) birth defects, and 1872 (90% PI, 1239–2415) perinatal deaths annually.13 The discounted lifetime health costs averted for the affected cohort of children was estimated to be as high as US$4.3 billion (90% PI, US$3.4–5.1 billion).

This type of extensive modelling has not been performed specifically for pre-pregnancy obesity in Australia, but a Queensland-based study found that maternal pre-pregnancy obesity was associated with an increase in the mothers’ hospital costs above those of normal weight women of $5 002 283.14

In 2006, the US Centers for Disease Control launched the world’s first national policy on pre-conception care.15 It focuses on individual responsibility for pre-conception health, as well as on the roles of clinicians, government and health care systems. National policies have also been published in the Netherlands, the United Kingdom and Italy. In Australia, only South Australia has released a specific policy, although pre-conception care is addressed in guidance documents produced by the Royal Australian and New Zealand College of Obstetricians and Gynaecologists16 and the Royal Australian College of General Practitioners.17 Implementing these policies is challenging, as capturing those who will become pregnant is not straightforward: one-third of pregnancies that continue to antenatal care are unplanned.18 Further, changes that require complex behavioural modification prior to pregnancy, such as weight loss, are less likely to be implemented than simple measures, such as folic acid supplementation.19 Another significant problem is the lack of evidence on which to base recommendations about weight loss and lifestyle interventions before pregnancy for improving maternal and neonatal outcomes; randomised trials concerned with pre-pregnancy weight have thus far focused on obesity and reduced fertility.20

Despite a lack of robust evidence about optimal pre-conception programs and interventions, a number of international bodies, including the US Academy of Nutrition and Dietetics,21 have published position papers advocating that women be better informed about the risks associated with pre-pregnancy obesity, and that behavioural counselling be provided to improve the diet and physical activity of obese women of reproductive age. We recognise that understanding of the maternal and neonatal consequences of obesity in Australia is deficient.22 A pragmatic approach may be to start with programs that enhance a woman’s knowledge of the consequences of obesity during pregnancy and the post partum period, and to inform women about postnatal programs that can reduce the risk of post partum weight retention, and therefore obesity during subsequent pregnancies. The most effective interventions include both dietary and exercise components.23 This approach will require hospitals and health services to take a more long term perspective of pregnancy and the post partum period, as well as government investment in these public health strategies.

Obesity, however, involves a complex interplay of biological and social vulnerabilities in different environments and population groups and at different life stages. Interventions at the level of the individual will need to be combined with system-level changes that promote preference 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.24

If current trends persist, about 80% of all Australian adults and one-third of Australian children will be overweight or obese by 2025.25 Supporting research into the most effective pre-conception interventions and strategies to arrest this trend is a key recommendation of the World Health Organization in the Report of the Commission on Ending Childhood Obesity, and this deserves thoughtful consideration.8

Authors

  • Kirsten I Black1,2
  • Adrienne Gordon2,3
  • 1. University of Sydney, Sydney, NSW
  • 2. Royal Prince Alfred Hospital, Sydney, NSW
  • 3. Charles Perkins Centre, University of Sydney, Sydney, NSW

Correspondence: kirsten.black@sydney.edu.au

Competing interests

No relevant disclosures.

References

Provenance: Not commissioned; externally peer reviewed.

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