Poor Outcomes Tied to Missing Mark for Gestational Weight Gain

Troy Brown, RN

June 08, 2017

Gestational weight gain above or below recommended amounts is associated with increased risk for adverse maternal and infant outcomes compared with weight gain within recommended levels, a new systematic review and meta-analysis of more than 1.3 million pregnancies has found. The researchers caution that no causal relationships can be concluded, however.

"Compared with recommended gestational weight gain, gain below guidelines was associated with 5% higher risk of both [small for gestational age (SGA)] and preterm birth and 2% lower risk of both [large for gestational age (LGA)] and macrosomia," the researchers write. "Weight gain above guidelines was associated with 3% lower risk of SGA and 2% lower risk of preterm birth and 4%, 6%, and 4% higher risk of LGA, macrosomia, and cesarean delivery, respectively."

The researchers also found that 47% of women studied had gestational weight gain greater than 2009 Institute of Medicine recommendations, and 23% had lower-than-recommended gestational weight gain.

Rebecca F. Goldstein, MBBS, FRACP, from the Monash Centre for Health Research and Implementation, Monash University, and Monash Diabetes and Endocrine Units, Monash Health, both in Victoria, Australia, and colleagues report their findings in an article published online June 6 in JAMA.

The researchers included 23 studies, of which 18 were retrospective and five were prospective. Ten studies were conducted in the United States, eight in Asia (four from China, two from Korea, and one each in Taiwan and Japan), and five in Europe (one each in Norway, Belgium, Italy, Denmark, and Sweden). The number of women included in each study ranged from 1034 to 570,672.

Eleven studies assessed SGA, 13 studies assessed LGA, 11 studies assessed macrosomia, and eight studies assessed cesarean delivery.

Lower-Than-Recommended Weight Gain

Compared with recommended weight gain, gestational weight gain below the recommended amount was associated with higher risk for SGA (odds ratio [OR], 1.53 [95% confidence interval (CI), 1.44 - 1.64]; absolute risk difference [ARD], 5% [95% CI, 4% - 6%]) and preterm birth (OR, 1.70 [95% CI, 1.32 - 2.20]; ARD, 5% [95% CI, 3% - 8%]). The association with SGA was most pronounced in women with lower prepregnancy body mass index.

Women with lower-than-recommended weight gain had lower risk for LGA (OR, 0.59 [95% CI, 0.55 - 0.64]; ARD, −2% [95% CI, −10% to −6%]) and macrosomia (OR, 0.60 [95% CI, 0.52 - 0.68]; ARD, −2% [95% CI, −3% to −1%]). The association with LGA was significant for underweight and normal weight women. The association with macrosomia was highest in underweight women.

There was no significant difference in the risk for cesarean delivery (OR, 0.98 [95% CI, 0.96 - 1.02]; ARD, 0% [95% CI, −2% to 1%]).

Higher-Than-Recommended Weight Gain

Gestational weight gain that exceeded recommendations was associated with lower risk for SGA (OR, 0.66 [95% CI, 0.63 - 0.69]; ARD, −3% [95% CI, −4% to −2%]) across prepregnancy body mass index categories. Women with weight gain above recommendations also had lower risk for preterm birth (OR, 0.77 [95% CI, 0.69 - 0.86]; ARD, −2% [95% CI, −2% to −1%]) and higher risk for LGA (OR, 1.85 [95% CI, 1.76 - 1.95]; ARD, 4% [95% CI, 2% - 5%]). The association with LGA increased as body mass index decreased.

Risk was also increased for macrosomia (OR, 1.95 [95% CI, 1.79 - 2.11]; ARD, 6% [95% CI, 4% - 9%]) and cesarean delivery (OR, 1.30 [95% CI, 1.25 - 1.35]; ARD, 4% [95% CI, 3% - 6%]). The association with macrosomia "was strongest in underweight women according to the ORs, and all associations were significant according to the ARDs," the researchers write. The ARD for cesarean delivery was significant for only underweight women.

Six studies assessed gestational diabetes mellitus, but definitions were inconsistent, and the studies reported different findings for gestational weight gain that exceeded guidelines and gestational diabetes mellitus risk.

The researchers determined three studies to have moderate bias risk and 20 to have low bias risk. "Reasons for moderate bias risk included self-reported final weight (detection bias), self-reported outcome measures (detection bias), failure to report all outcomes (report bias), and insufficient adjustment for confounding variables (confounding bias)." All but four studies reported no conflict of interest.

Limitations of this study include that it contained no studies in developing countries or non-English-language articles. Some outcomes were assessed by only a single study, which prevented the researchers from conducting a meta-analysis. "Findings from this review are based on observational data and no causal links may be concluded. They may be applicable on a population level, but recommendations need to be individualized when applied clinically," the authors write.

Emphasizing Negative Effect on Developing Baby May Be Best Bet

"These estimates were based on large cohort studies, so even though the associations were consistent and strong, the causal relationship between weight gain in pregnancy and outcomes cannot be established," Aaron B. Caughey, MD, PhD, from the Department of Obstetrics and Gynecology, Oregon Health & Science University, Portland, writes in an accompanying editorial.

"Although interventions to limit weight gain during pregnancy are effective, the magnitude of benefit is modest," Dr Caughey says.

And although limiting gestational weight gain may improve short-term outcomes in pregnancy, "the effect on outcomes beyond the immediate postpartum period is less clear," he adds.

When encouraging women to modify their behavior, loss avoidance may be a stronger motivator than offering a reward for adherent behavior, Dr Caughey proposes. "[R]ather than positive incentives for adherent behavior, emphasizing how a pregnant woman's nonadherent behavior will lead to greater harm to her developing baby may be more effective in changing behavior," he explains. "Sending a message that gaining too much weight could potentially lead to an increased risk of obesity in her child and that gaining too little weight could lead to growth restriction in the child may be better than a simple positive message that eating well leads to greater health for both the mother and infant."

One author reports serving on the Women's Health Global Advisory Board for Pfizer. The remaining authors and Dr Caughey have disclosed no relevant financial relationships.

JAMA. Published online June 6, 2017. Article abstract, Editorial extract

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