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Maternal obesity ‘increases risk of infant death’

Recent studies have found conflicting evidence on whether there is an association between infant mortality and overweight and obesity in mothers. Some analyses found that there was an increased risk of infant mortality if the body mass index (BMI) of the mother was 30 or over, though others were inconclusive.

baby in womb
The researchers suggest that 11% of infant deaths in the study were associated with maternal overweight and obesity.
The researchers behind the new study analysed data from over 1.8 million births between 1992 and 2010 recorded as part of the Swedish Medical Birth Register. In the study, maternal BMI was classified as follows:

Underweight (BMI of 18.4 or less)
Normal weight (18.5-24.9)
Overweight (25-29.9)
Obesity grade 1 (30-34.9)
Obesity grade 2 (35-39.9)
Obesity grade 3 (40 or over).
During the study period, a total of 5,428 infant deaths occurred. The researchers found that two thirds of the deaths occurred during the first 28 days of life.

‘Rates of infant mortality increased with increasing maternal BMI’
Among “normal weight” women, there were 2.4 infant deaths per 1,000 births, and among women with obesity grade 3, there were 5.8 infant deaths per 1,000 births. Rates of infant mortality increased with increasing maternal BMI.

Compared with normal weight mothers, infant mortality was described as being “modestly increased” among overweight and mildly obese mothers. However, the study found that mothers with obesity grade 2 or 3 had more than doubled risks of experiencing infant death.

The majority of infant deaths in the sample group (81%) were caused by congenital anomalies, birth asphyxia, sudden infant death syndrome (SIDS) or infections.

Risk of birth asphyxia and other neonatal conditions increased in accordance with the BMI of the mothers. Infants of mothers who were classified as being in the obesity grade 2-3 groups were found to have increased risk of dying from congenital abnormalities and SIDS.

The researchers suggest that 11% of infant deaths in the study were associated with maternal overweight and obesity.

The association between maternal BMI and infant death was reported mostly in term births of at least 37 weeks gestation. Associations between maternal BMI and infant death in preterm births were only reported among obesity grade 2-3 mothers.