Infants born in 2020 through mid-2021 to women with COVID-19 weighed less at birth, but grew at a faster rate than a comparable group born to women who did not have COVID-19, according to a study funded by the National Institutes of Health. Previous studies have found that preterm infants and other infants who are small or underweight at birth and who undergo catch-up growth in the first year are at higher risk for later life obesity, heart disease, high blood pressure and diabetes, compared to infants born at normal weight. The authors called for additional studies of infants whose mothers had COVID-19 during pregnancy to learn if they have increased health risks later in life.

The study was conducted by Andrea Edlow, M.D., and Lindsay Fourman, M.D., of Massachusetts General Hospital, and colleagues. It appears in The Journal of Clinical Endocrinology and Metabolism. NIH funding was provided by the Eunice Kennedy Shriver National Institute of Child Health and Human Development with additional support from the National Heart, Lung, and Blood Institute, the National Institute of Diabetes and Digestive and Kidney Diseases, and the National Institute of Allergy and Infectious Diseases.

According to the U.S. Centers for Disease Control and Prevention, in 2020, pregnant women comprised 9% of reproductive aged women with COVID-19. Compared to nonpregnant females of similar age, pregnant people with COVID-19 are more likely to experience severe disease, more likely to be admitted to an intensive care unit, and more likely to need mechanical ventilation to help them breathe. Mothers with COVID-19 are more likely than those without the infection to give birth preterm and to have hypertensive disorders of pregnancy. Moreover, placentas from pregnancies complicated by COVID-19 are often inflamed at the junction between the maternal and fetal parts of the placenta and contain higher amounts of immune cells from mother and fetus.

Despite these ill effects, pregnant people with COVID-19 are unlikely to pass the virus on to their babies. However, few studies have been conducted on the potential long-term effects that may be experienced by children born to mothers with COVID-19 during pregnancy.

For the current study, researchers compared weight, length, and body mass index (BMI) at birth, 2 months, 6 months, and 12 months of 149 babies born to mothers with COVID-19 during pregnancy to those of 127 babies born to mothers without any symptoms of COVID-19. For each infant, researchers calculated a z-score for each of the three measures. Z-scores are a comparison measure of an individual to a formal standardin this case, average weight, length, and body measurements compiled as growth charts by the World Health Organization.

At birth, infants born to mothers with COVID-19 and those born to mothers without COVID-19 did not differ in average z-scores for length. However, those exposed to COVID-19 during pregnancy had an average birth weight z-score that was 30% lower than those not exposed and a BMI z-score that was 35% lower than that of the unexposed infants. By 12 months, infants exposed to COVID-19 in the uterus had a 53% greater gain in BMI z-score than the infants not exposed to COVID-19.

Although preterm infants often have a similar pattern of accelerated growth in comparison to term infants, the authors did not find preterm birth to be the cause of the rapid growth they saw in their study, as the z-scores considered gestational age at birth, and the study did not include enough preterm infants to account for the difference.

In fact, the difference between the two groups persisted, even after researchers statistically compensated for factors known to influence infant size, such as the mothers age and BMI.

The pattern of catch-up growth seen in infants exposed to COVID-19 during pregnancy may place them at risk for heart disease and other obesity-related illnesses later in life. The findings underscore the need to prevent COVID-19 in pregnant people using such protective measures as vaccination and wearing masks indoors, before and during pregnancy.

Ockene, MW, et al. Accelerated longitudinal weight gain among infants with in utero COVID-19 exposure. The Journal of Clinical Endocrinology & Metabolism. 2023.

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