Prevent Excessive Weight Gain in Pregnancy for Kids' Bone Health

Nancy A. Melville

November 09, 2018

There was no clear association between putting on the pounds during pregnancy and bone health of offspring at 7 years of age, according to a new study of more than 2000 mother-child pairs in Portugal. The findings contradict some theories that efforts to keep gestational weight gain in check could have an adverse effect on child bone health.

"Until recently, it was a widely held scientific belief that any weight gain from the mother during pregnancy would have a beneficial effect on children's bone mass," lead author Teresa Monjardino, MD, of the Universidade do Porto, Portugal, said in a press statement. The study was published online November 6 in the Journal of Bone and Mineral Research.

"Our study results corroborate that there is no benefit in gaining weight above the US Institute of Medicine (IOM) recommendations for pregnancy weight gain for children's bone mass, in both normal and overweight women prior to pregnancy," she said.

Given the known adverse effects of excessive gestational weight gain on various aspects of maternal and offspring health, particularly with respect to the child's cardiometabolic risk, the IOM recommendations on weight gain are a standard component of prenatal care.

In light of some evidence linking gestational weight gain with positive effects on the bone mass of offspring, Monjardino and her colleagues analyzed prospective data on 2167 mother and child pairs from the longitudinal Generation XXI birth cohort in Portugal. The data included results from whole-body dual-energy X-ray absorptiometry for the children at age 7.

If Overweight, No Benefit of Excessive Weight Gain to Childhood Bone

Monjardino and colleagues found that pregnant mothers who were underweight or of normal early weight, as indicated by body mass index (BMI), gestational weight gain was associated with a slight increase in the mean bone measures of offspring at age 7 (Z-scores per 5 kg of gestational weight gain: bone mineral content [BMC], 0.07; bone area density [aBMD], 0.10; size-corrected BMC [scBMC], 0.11; height, 0.05).

Among mothers who were overweight or obese in early pregnancy (38.5% of total), however, no effect of gestational weight gain was observed on offspring bone health (Z-scores per 5 kg of gestational weight gain: BMC, 0.02; aBMD, 0.02; scBMC, 0.01; height, 0.02).

"Results remained practically unchanged after adjustment for maternal age, height and educational level, and gestational age of the offspring," the authors say.

The mean maternal gestational weight gain among the mothers overall was 29.3 lb (13.3 kg ± 5.3 kg). The weight gain was greater among those who were underweight or of normal weight in early pregnancy compared to those who were overweight or obese (14.1 kg vs 11.7 kg; P < .001).

In more than a third of the births (36.6%), the mothers experienced weight gain during pregnancy that exceeded IOM recommendations; in 23.7% of births, the mothers' gestational weight gain was insufficient.

"We found a modest direct linear association between maternal gestational weight gain and bone mineralization in the offspring of women who were under/normal weight in early pregnancy, possibly reflecting a weak biological effect," the authors conclude.

"However, among overweight/obese women, increased GWG [gestational weight gain] had no apparent relation with offspring bone mineralization. The corresponding causal interpretation would be that there is little or no apparent advantage of gaining excess weight during pregnancy for offspring bone health, particularly in women with excessive weight in early pregnancy," they write.

Maternal Weight/Offspring Bone Measures From Other Studies

Monjardino and her colleagues note that some theories could indeed explain a beneficial effect of weight gain on the bone health of offspring.

"By altering the intrauterine environment, including nutrient availability or endocrine factors such as leptin and estrogen, GWG may influence not only fetal bone formation, but also the programming of bone strength during childhood and even later in life," they say.

Previous studies have shown a positive association between maternal weight during pregnancy and bone health of offspring. The Southampton Women's Survey showed particularly notable associations between maternal fat stores in late pregnancy and offspring bone mineral density and geometry at birth.

Other research, such as the Generation R Study, which included 6-month-old infants, and a study of nearly 12,000 Chinese children aged 0 to 3 years, has linked gestational weight gain with bone mineral density.

The new study is believed to be the first to specifically investigate early pregnancy BMI in relation to offspring bone associations, the authors state.

"To the best of our knowledge, no studies have looked at the potential effect modification by maternal early pregnancy BMI on gestational weight gain/bone associations," they write.

The results suggest that, at least in terms of offspring bone mass, efforts to prevent excessive weight gain in pregnancy are not detrimental.

"At the policy level, our findings reinforce IOM guidelines for weight gain," they stress. "At the clinical practice level, this study supports the inclusion of bone health in the context of weight counselling during pregnancy."

Study coauthor Cyrus Cooper, DM, has received personal fees from the Alliance for Better Bone Health, Amgen, Eli Lilly, GSK, Medtronic, Merck, Novartis, Pfizer, Roche, Servier, Takeda, and UCB outside of the current study. The other authors have disclosed no relevant financial relationships.

J Bone Miner Res. Published November 6, 2018. Abstract

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