Maternal obesity increases the risk for unexpected sudden infant death

Key takeaways:

• The risk for sudden unexpected infant death rose as maternal obesity severity increased.
• Specific mechanisms behind the associations have not been identified.

Maternal obesity may be linked to increased risk for sudden unexpected infant death, results from a cohort study in JAMA Pediatrics suggest.

The findings reveled a dose-dependent relationship between increasing BMI among mothers of infants and the risk for sudden unexpected infant death (SUID).

Healio previously reported research that identified an association between higher BMIs before pregnancy and multiple adverse health outcomes, including maternal morbidity, preeclampsia and gestational hypertension.

“Maternal obesity is also a known risk factor for general infant mortality, but there was very little existing research on a potential relationship between maternal obesity and SUID risk,” Darren Tanner, PhD, from the AI for Good Research Lab at Microsoft, told Healio. “The few studies that had considered this had inconsistent results. But when we reviewed the literature, we noted that the studies were fairly small. This can make it hard to detect trends and associations.”

In the study, the researchers examined a cohort of 18,857,694 live births between 2015 and 2019 using CDC National Center for Health Statistics data.

BMI before pregnancy was categorized as underweight (less than 18.5 kg/m²), normal weight (18.5 to 24.9 kg/m²), overweight (25 to 29.9 kg/m²), class I obesity (30 to 34.9 kg/m²), class II obesity (35 to 35.9 kg/m²) or class III obesity (40 kg/m² or greater).

Overall, 5.4% of the 16,545 SUIDs during the study period were attributable to maternal obesity.

Tanner and colleagues found that infants born to mothers with obesity had a higher SUID risk compared with mothers with normal BMI after confounder adjustment.

This risk increased as obesity severity rose, as adjusted ORs for SUID were 1.1 (95% CI, 1.05-1.16) among infants with mothers with class I obesity, 1.2 (95% CI, 1.13-1.27) among infants with mothers with class II obesity and 1.39 (95% CI, 1.31-1.47) among infants with mothers with class III obesity.

A generalized additive model showed that increased BMI was monotonically associated with increased SUID risk, with an acceleration of risk for BMIs around 25 to 30 kg/m², the researchers wrote.

Tanner and colleagues suggested that obstructive sleep apnea (OSA) may be one possible mechanism behind the association.

OSA “can result in intermittent hypoxia, which is known to cause oxidative stress, in turn having detrimental consequences on fetal growth,” they wrote. “Fetal growth restriction can increase the postnatal risk of neurodevelopmental and cardiometabolic disorders, which could cause an arousal defect, thus increasing the infant’s risk of death.”

However, the researchers could not assess either OSA or bed-sharing — another suggested mechanism — meaning that specific mechanisms were not identified.

Tanner said that once mechanisms have been determined in future research, “more work will then be needed to identify strategies that might reduce obesity-related risks for SUID.”

“SUID is a rare event and the additional risk associated with obesity is small,” he told Healio. “It’s only at the population level where obesity-related risks become a large concern.”