Breastfeeding Intensity Linked to Growth in GDM-Exposed Infants

Key Takeaways

• Among infants exposed to gestational diabetes in utero in the SWIFT Offspring cohort, higher cumulative breastfeeding intensity was associated with lower odds of accelerated weight-for-length growth across infancy.
• Higher cumulative breastfeeding intensity was also associated with a lower likelihood of later accelerated weight-for-age growth by 12 months.
• Primary latent class analyses did not show an association between breastfeeding intensity and raw summed, triceps, suprailiac, or subscapular skinfold trajectory class membership.
• Secondary analyses suggested small inverse associations between greater cumulative breastfeeding intensity and subscapular and triceps skinfold z-score change from 6 to 12 months.

Whether the amount of breastmilk across mixed and exclusive feeding patterns relates to early growth remains a practical question for infants exposed to gestational diabetes (GDM) in utero, a group with concern about later excess weight gain and adiposity. Instead of treating feeding as a simple yes-or-no exposure, investigators tracked breastfeeding intensity across the first year alongside repeated measures of infant size and body composition. They then examined how month-by-month feeding patterns aligned with changing growth trajectories over infancy.

Investigators analyzed the prospective SWIFT Offspring cohort study of breastfeeding intensity and first-year growth trajectories in GDM-exposed infants, which included singleton infants exposed to gestational diabetes in utero and enrolled from 2009 to 2011 at Kaiser Permanente Northern California hospitals. The analytic sample included 435 infants after 29 of 464 enrolled infants were excluded for insufficient repeated anthropometric data. Breastfeeding exposure was collected prospectively with diaries, mailed monthly surveys, and in-person surveys and summarized as the lactation intensity ratio (LIR), defined as breastfeeding divided by breastfeeding plus formula feedings over the prior 7 days on a 0-to-1 scale, and as cumulative summed lactation intensity ratio (sumLIR) across months 1 through 12. Anthropometry at birth and at 6 to 9 weeks, 6 months, and 12 months supported latent class mixed modeling of weight-for-age z-score, length-for-age z-score, weight-for-length z-score, and skinfold trajectories, with adjusted multinomial logistic regression and a secondary linear regression of skinfold z-score change used to relate feeding intensity to growth patterns.

In breastfeeding intensity and first-year growth trajectories in GDM-exposed infants, five weight-for-length trajectory classes were identified, including a highly accelerated class that rose by more than 2 standard deviations from birth to 6 months. Higher cumulative breastfeeding intensity was associated with lower odds of membership in less favorable weight-for-length classes across infancy, with a sumLIR odds ratio of 0.11 (95% confidence interval 0.02-0.54) for class 3 versus class 2 at 1 month and 0.84 (95% confidence interval 0.75-0.95) at 12 months. Higher cumulative breastfeeding intensity was also associated with lower odds of membership in the later accelerated weight-for-age class at 12 months, with an odds ratio of 0.91 (95% confidence interval 0.84-0.99), while the class 4 weight-for-length association was directionally similar.

Adiposity findings were more limited. Primary latent class analyses of raw summed, triceps, suprailiac, and subscapular skinfold trajectories showed no association between monthly or cumulative breastfeeding intensity and trajectory class membership. In a secondary linear regression subset analysis among 318 infants, higher 12-month cumulative breastfeeding intensity was associated with subscapular skinfold z-score change beta -0.03 (95% confidence interval -0.07 to -0.003) and triceps skinfold z-score change beta -0.05 (95% confidence interval -0.08 to -0.01) from 6 to 12 months. These secondary adiposity signals were smaller and remained subordinate to the weight-trajectory findings.

Breastfeeding exposure was self-reported despite prospective collection, skinfold z-scores were unavailable before 3 months so raw skinfold values were used in the trajectory models, maternal prenatal diet was not included, and the cohort was limited to dyads exposed to gestational diabetes. The observational design supports association reporting rather than causation. Because the cohort came from Kaiser Permanente Northern California and was described as representative of diverse U.S. births to women with gestational diabetes, the findings are most directly relevant to that U.S. population.

The authors concluded that greater lactation intensity, including within mixed-feeding patterns, was associated with more favorable first-year weight-for-length trajectories in infants exposed to gestational diabetes in utero. They also reported inverse associations with later weight-for-age acceleration and with secondary skinfold change analyses. The main signal was a more favorable early growth pattern with greater breastfeeding intensity in this gestational-diabetes-exposed cohort.

Clinician Questions

How was breastfeeding intensity measured in the SWIFT Offspring infants exposed to gestational diabetes?

Breastfeeding intensity was measured monthly as the lactation intensity ratio, calculated as breastfeeding occurrences divided by breastfeeding plus formula feedings over the prior 7 days on a 0-to-1 scale. Cumulative exposure was then summarized as the summed lactation intensity ratio across months 1 through 12.

Which infants do the SWIFT Offspring breastfeeding findings apply to?

These findings apply to singleton infants exposed to gestational diabetes in utero who were born at 35 weeks gestation or later to mothers with gestational diabetes diagnosed by Carpenter and Coustan criteria and enrolled through Kaiser Permanente Northern California. They describe this gestational-diabetes-exposed population rather than all infants.

Why were the primary skinfold trajectory results and the secondary skinfold z-score analyses different outcomes?

The primary models classified raw triceps, suprailiac, subscapular, and summed skinfold patterns across infancy, and breastfeeding intensity was not associated with triceps or subscapular trajectory class membership in those primary analyses. By contrast, the secondary analysis examined change in subscapular and triceps skinfold z-scores from 6 to 12 months. That difference arose because World Health Organization skinfold z-scores were unavailable before 3 months, which limited use of standardized skinfold outcomes earlier in infancy.