Infants born to mothers with obesity may be at a higher risk of sudden unexpected infant death (SUID), according to a nationwide cohort study published in JAMA Pediatrics. The risk seemed to increase with the severity of maternal obesity in a dose-dependent manner, according to the report.
Researchers analyzed data from 18,857,694 live births in the U.S. from 2015 through 2019, from which 16,545 infants died of SUID, resulting in an overall SUID rate of 0.88 per 1,000 live births. Among the study population, 3.3% of mothers were underweight (body mass index [BMI] = < 18.5), 42.1% had a normal BMI (range = 18.5-24.9), 25.6% were overweight (BMI = 25.0-29.9), 14.4% had class I obesity (BMI = 30.0-34.9), 7.0% had class II obesity (BMI = 35.0-39.9), and 5.0% had class III obesity (BMI = ≥ 40.0).
After adjusting for confounders, infants born to mothers with class I obesity had a 10% higher risk of SUID (adjusted odds ratio [aOR], 1.10; 95% CI, 1.05-1.16) compared to those born to mothers with a normal BMI. The SUID risk was 20% higher for infants of mothers with class II obesity (aOR, 1.20; 95% CI, 1.13-1.27) and 39% higher for those with mothers with class III obesity (aOR, 1.39; 95% CI, 1.31-1.47). The univariate analysis also showed increased odds of SUID among infants whose mothers were underweight (OR, 1.40; 95% CI, 1.29-1.52) and for those whose mothers who were overweight or obese, with increasing obesity classes associated with higher odds of SUID (overweight: OR, 1.06, 95% CI, 1.02-1.10; class I obesity: OR, 1.33, 95% CI, 1.27-1.39; class II obesity: OR, 1.57, 95% CI, 1.48-1.66; class III obesity: OR, 1.97, 95% CI, 1.86-2.09).
A generalized additive model showed that increased maternal BMI was monotonically associated with increased SUID risk, with an acceleration of risk for BMIs greater than approximately 25 to 30. The findings were consistent across the three SUID cause of death classifications (ICD-10 codes R95, R99, and W75) and remained significant after adjusting for gestational age at birth. Infants born at a gestational age between 28 and 31 weeks (aOR, 2.84; 95% CI, 2.60-3.11) and between 32 and 36 weeks (aOR, 1.93; 95% CI, 1.85-2.01) had higher SUID odds than infants born at 37 weeks' gestation or later.
The population attributable fraction (PAF) analysis revealed that approximately 5.4% of SUID cases were attributable to maternal obesity, corresponding to about 179 SUID cases per year in the U.S.. The adjusted PAFs for each obesity class were as follows: class I obesity: 0.015 (95% CI, 0.008-0.023), class II obesity: 0.016 (95% CI, 0.011-0.020), and class III obesity: 0.023 (95% CI, 0.020-0.027).
"Based on our results, maternal obesity should be added to the list of known risk factors for SUID," stated lead study author Darren Tanner, PhD, of the AI for Good Research Lab at Microsoft Corporation. "As the obesity epidemic continues to accelerate, maternal obesity is likely to play an increasingly larger role in SUID prevalence over time."
The study's strengths include its large sample size—with more than 16,000 SUID cases and 18 million births—and the ability to adjust for a large number of confounders. E-values suggest that residual confounding would need to be substantial to account for the observed associations. For example, an unmeasured confounder associated with at least a twofold increased risk of both obesity class III and SUID would be needed to erase the observed aOR of 1.39. However, the researchers noted that the study did not include direct measures of bed sharing or sleep apnea, which could potentially contribute to the obesity-SUID association.
"Future work is needed to elucidate the specific causal mechanisms for the obesity-SUID association," said Dr. Tanner. "Such research could lead to interventions that reduce or eliminate a nontrivial proportion of unexpected infant deaths."
Conflict of interest disclosures can be found in the study.
