Early Weight Gain in Pregnancy May Be Bad Start for Infant

Laird Harrison

July 15, 2013

Mothers who put on too much weight early in their pregnancies have bigger, fatter babies, a new study shows.

The neonates born to women who gained too much early in their pregnancies had a mean body mass index (BMI) of 14.5 ± 1.3 kg/m2 compared with 12.6 ± 1.2 kg/m2 for the neonates of women whose weight gain was appropriate, and 13.2 ± 1 kg/m2 for the neonates of women who gained too much late in their pregnancies.

"Implementing preventive measures in the period before conception or in early pregnancy may be necessary to prevent early excessive gestational weight gain and its potential detrimental effects on the neonate," write Margie H. Davenport, PhD, from the Physical Activity and Diabetes Laboratory, Li Ka Shing Centre for Health Research Innovation, University of Alberta, Edmonton, Canada, and colleagues.

The study was published online July 8 and in the August issue of Obstetrics and Gynecology.

Previous research has shown that a mother's weight can affect the health of her baby and that events in pregnancy can have a lifetime effect on the child's health. However, few studies have looked at the timing of weight gain.

To examine this question, the investigators recruited 172 healthy women who were between 16 and 20 weeks pregnant. The women followed healthy living guidelines, but many of them still gained excessive weight.

Researchers categorized them, using 2009 Institute of Medicine guidelines, into 4 groups: 33 patients whose weight gain was appropriate throughout their pregnancy, 49 whose weight gain was excessive late in their pregnancy, 29 whose weight gain was excessive in the first half of their pregnancy, and 61 whose weight gain was excessive overall.

The researchers found that total maternal prepregnancy BMI correlated with total maternal weight gain, neonatal birth weight, and neonatal BMI. However, even after controlling for maternal prepregnancy BMI, they found that the correlation between total maternal weight gain and neonatal body fat remained statistically significant (P = .047).

Moreover, when the investigators compared infants whose mothers gained excessive weight early in pregnancy with those whose mothers gained excessive weight late in pregnancy, they found statistically significant (P < .05) differences in the infants’ weight, the percentage of those with a weight of at least 4000 g, the infants’ crown-to-heel length, and the infants’ BMI.

The investigators saw the same statistically significant differences (P < .05) when they compared newborns from mothers whose weight gain came early and those who gained an appropriate weight.

Likewise, the newborns of those mothers whose overall weight gain was excessive differed significantly from those whose weight gain was appropriate or came late by the same measures. In addition, it differed significantly in suprailiac skinfold.

Why does early weight gain affect the size and fat of the newborn? The babies might simply be inheriting their mothers' characteristics, the researchers note. However, they also point out that an earlier study found that even small differences in weight between pregnancies increased the probability of newborns who were large for their gestational age.

"This suggests that environmental factors play an important role in neonatal growth," they conclude.

The authors have disclosed no relevant financial relationships.

Obstet Gynecol. Published online July 8, 2013. Abstract

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