More than 5% of cases of sudden infant death may be linked to maternal obesity, new research showed.
“When a parent has a child that dies of sudden unexplained infant death [SUID], it’s extremely devastating,” said Jan-Marino Ramirez, PhD, the Zain Nadella Endowed Chair in Pediatric Neurosciences at the University of Washington, Seattle, and director of the Center for Integrative Brain Research at Seattle Children’s Hospital. “And the most devastating problem is that there’s no clear answer. Understanding the mechanisms will help parents understand.”
The study was published online in JAMA Pediatrics.
In the United States, approximately 3500 cases of SUID are reported yearly. After educational campaigns in the 1990s demonstrating safe infant sleep positions, rates of these fatalities dropped but have since plateaued.
Maternal Obesity During Pregnancy
Rates of maternal obesity are increasing globally, and more than half of women of reproductive age are overweight or obese.
“Maternal obesity before pregnancy affects placental development, gene expression, and has long-term implications,” said Patrick Catalano, MD, a professor in residence at the Departments of Reproductive Endocrinology and Obstetrics and Gynecology at Massachusetts General Hospital and Harvard Medical School in Boston.
Maternal obesity is a well-documented risk factor for adverse outcomes of pregnancy including stillbirth, preterm birth, and admission to the neonatal intensive care unit. Swedish researchers in 2014 reported maternal obesity was linked to an increase in infant mortality that increased with body mass index (BMI), but that study did not look specifically at SUID.
For their new study, Dr. Ramirez and colleagues looked at data from all live births in the United States from 2015 to 2019 recorded by the Centers for Disease Control and Prevention and the National Center for Health Statistics. Of the 18,857,694 live births occurring at 28 weeks of gestation or later, 16,545 infants died of a sudden, unexplained cause.
Rates of SUID in babies born to mothers with obesity increased in a statistically significant, dose-dependent manner relative to normal weight mothers. The unadjusted absolute risks for SUID were 0.74 cases per 1000 births for normal weight mothers, 0.99 cases at BMIs between 30 and 35, 1.17 cases at BMIs between 35 and 40, and 1.47 instances at BMI ≥ 40.
After adjustment for maternal age, race, ethnicity, and level of education, the adjusted odds ratio for a case of SUID was 1.39 among women with the highest levels of obesity (95% CI, 1.31-1.47), according to the researchers.
While the study revealed an association between maternal obesity and SUID, the basis for this connection remains unknown, the investigators noted. One possibility for the link is that obesity increases the risk for obstructive sleep apnea, which can result in intermittent hypoxia. That, in turn, causes oxidative stress, which may possibly have effects on the fetus causing effects that eventually lead to SUID in the infant.
An accompanying editorial by Jacqueline Maya, MD; Marie-France Hivert, MD, MMSc; and Lydia Shook, MD, from the Massachusetts General Hospital and Harvard Medical School, suggested that the SUID is unlikely directly influenced by high maternal BMI but rather by the metabolic concerns related to obesity such as inflammation, insulin resistance, and abnormal lipid metabolism. Epigenetics may also play a role.
“We believe the evidence for this study of an association between prepregnancy obesity and SUID is a call to action for the scientific and medical community to better understand the complex interplay of biological, social, and behavioral factors that may lead to SUID, a devastating complication that no family should experience,” the authors of the editorial wrote.
Dr. Ramirez stressed the importance of not initiating guilt because there are many factors in SUID such as genetics that cannot be controlled.
“We are far from saying a baby died because you were obese; that’s an important message to parents,” he said. What he sees as important, rather, is using this new research to elucidate further mechanisms that may allow for more targeted interventions: “If we discover that it’s due to, for example, sleep apnea, that’s something we can prevent.”
The researchers reported no conflicts of interest.
A version of this article first appeared on Medscape.com.