Weight gain recommendations in pregnancy

The prevalence of obesity in the USA and in most European countries is 30–40% [1]. The growing prevalence of obesity and related comorbidities has brought into question the current recommendations for weight gain in pregnancy and its effect on postpartum weight retention. The recommendations that are prescribed worldwide by obstetricians and healthcare providers were included in a report published by the Institute of Medicine (IOM) in 1990 [2]. The recommendations and report were based largely on observational studies of weight gain in pregnancy and expert opinion; the quality of evidence was level III and IV. The recommendations and report have focused primarily on prevention of low-birth-weight deliveries, which were at the time attributed primarily to deficient nutrition and/or insufficient weight gain during pregnancy. The recommendations and report have not addressed the other causes for growth restriction in uterus and did not distinguish between the different forms of growth restriction that could be diagnosed by ultrasound examination. Conversely, the recommendations have not considered the consequence of excessive weight gain on the fetus such as macrosomia and other factors, particularly in overweight and obese women. The IOM guidelines for obese women (prepregnancy BMI greater than or equal to 30.0 kg/m²) did not include an upper limit and did not distinguish between the different obesity classes and recommended to obese pregnant women as a whole to gain at least 15 lbs. We can certainly speculate that for overweight and obese pregnant women who gained at least 15 lbs during their pregnancies (and evidence suggests that they gain more) pregnancy has become a major contributing factor in the progression of their obesity, since the general tendency is to retain the weight postpartum. Studies have determined that gaining more than the recommended weight results in a two- to threefold further increase in weight retention postpartum [3]. The recommendations did not account for interactions between energy intake and energy expenditure. There is still a prevailing reluctance among healthcare providers to prescribe lifestyle modification in pregnancy that includes judicious diet and exercise.

The perception is that pregnancy is not an opportune time for such interventions because of potential (uncertain) risk to the fetus. Pregnancy has become, over the years, a state of indulgence and confinement. While the original intent was to prevent low-birth-weight deliveries in all pregnant patients, it appears important to point out that inadequate gestational weight gain will primarily affect birth weight in the underweight and normal weight pregnant women [4], but, by and large, not in overweight and obese women.

Weight gain in pregnancy varies widely among pregnant subjects and is influenced by pregravid weight and daily energy expenditure. Very little attention is being directed towards encouraging pregnant women to engage in physical activities in pregnancy. The IOM recommendations did not distinguish between energy intake and energy requirement of active and sedentary women. Critics argue that the 1990 IOM recommendations, which are higher than the previous guidelines, did not improve outcomes and actually resulted in increased adverse maternal and fetal outcomes. For obese pregnant women the comorbidities are as significant for the mother (hypertension, diabetes and operative deliveries) as for the fetus and neonate (stillbirths, congenital malformations, macrosomia, premature deliveries and traumatic deliveries). Studies have consistently demonstrated that increased prepregnancy BMI followed by excessive weight gain in pregnancy are significant risk for developing pre-eclampsia and gestational diabetes. The odd ratios of a stillbirth for overweight pregnant women are 1.47 (95% confidence interval [CI]: 1.08–1.94) and for obese pregnant women 2.07 (95% CI: 1.59–2.74) [5]. In a population-based cohort study, recently published data obtained from 120,251 Missouri birth-certificates (1990–2001) indicates that for class II and III obese pregnant women gestational weight gain of less than the currently recommended 15 lbs is associated with a significantly lower risk of pre-eclampsia, cesarian delivery and large for gestational age births, and the risks for small for gestational age fetus is minimal. The risk for low birth weight increases significantly for this group of patients only when the weight loss in pregnancy exceeds 10 lbs. The study, however, was not controlled for other causes of inadequate gestational weight gain (e.g., cigarette smoking, socioeconomic status or use of illegal substances) [6].

Gestational diabetes mellitus (GDM) is another comorbidity with a strong link to obesity. GDM affects on average 7% of all pregnancies, furthermore, those women who are morbidly obese have almost an 8.5-fold increased risk of developing GDM [7]. GDM not only increases the risk of adverse pregnancies and infant outcomes, but also is associated with a higher risk of developing Type 2 diabetes later in life in both the mother and offspring. Obese pregnant women who engage in physical activities during their pregnancies reduce their risk of developing GDM by 50% [8].

Long-term comorbidities persist in obese mothers and strong evidence is emerging for a causal chain of maternal–offspring obesity [9]. Recent studies suggests that increasing maternal hyperglycemia is associated with metabolic imprinting of the infant along with an increased future risk of childhood obesity by age 7 years and that treatment of GDM may be a modifiable risk factor in preventing childhood obesity [10]. A 2007 National Research Council (NRC) workshop on the influence of pregnancy weight on Maternal and Child Health report recognized that ‘gaps in knowledge have emerged even as additional data are collected and reported’ [11].

Future guidelines will have to focus not only on biological and metabolic factors but also on interactions between energy intake and energy expenditure. The 2007 NRC report makes only brief mention of the effect of physical/exercise activities on gestational weight gain [11]. The emerging strategy should also include behavioral modification interventions for obese pregnant women that include a prescription for an eucaloric or hypocaloric diet coupled with exercise prescription. Previous studies have demonstrated that engaging in exercise activities in pregnancy is safe [12]. Obese pregnant women should not be precluded from engaging in physical activities and diet should be modified to reduce emerging maternal comorbidities particularly hypertension and diabetes. Recently, interventions have been safely and successfully employed in overweight and obese pregnant women [13].

In the absence of complications all pregnant women should continue and maintain an active lifestyle, follow a judicious diet, to continue and derive health benefits while avoiding obesity-related comorbidities. The goal of nutritional intervention during pregnancy should be to decrease the risk for developing comorbidities and to cause a behavior change in eating habits and promote healthy eating patterns among the entire family. The optimal nutritional plan for pregnancy would provide adequate calories and nutrients to support fetal growth while limiting maternal weight-gain comorbidities. Pregnancy is an ideal time for behavior modification that includes physical activity and with proper medical supervision it can be safely prescribed. Interventions for identified benefits and risks should be pursued across the lifespan, preconception, pregnancy and postpartum [14]. Pregnancy is the time when women are motivated to make changes to improve their lifestyle, and is an optimal time for healthcare providers to offer their support through community resources to decrease maternal obesity, thus impacting the lives of future generations.

Financial & competing interests disclosure

The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

No writing assistance was utilized in the production of this manuscript.