# Maternal obesity phenotype, metabolic dysfunction, and preterm birth: a prospective birth cohort study

## TL;DR

This study shows that metabolic issues and being overweight or obese during pregnancy increase the risk of preterm birth, especially when both factors are present.

## Contribution

The study identifies a significant additive interaction between metabolic unhealthiness and overweight/obesity in increasing preterm birth risk.

## Key findings

- Women with metabolically unhealthy normal weight had a 1.33 times higher risk of preterm birth compared to metabolically healthy normal weight women.
- Overweight or obese women with metabolic issues had a 1.62 times higher risk of preterm birth.
- The combined effect of overweight/obesity and metabolic unhealthiness increased preterm birth risk 2.22 times compared to either risk alone.

## Abstract

The purpose of this research was to examine the relationship between metabolic obesity phenotypes and preterm birth (PTB) as well as the impact of obesity and metabolic abnormalities on PTB.

A total of 20,259 pregnant singleton women participated in prospective birth cohort research conducted in China. Obesity metabolic phenotypes were categorized using pre-pregnancy body mass index (BMI) and metabolic state. Any delivery before 37 full weeks of gestation, as determined by the best obstetric estimate available, was considered PTB.

As the number of metabolically unfavorable components grows, so does the risk of developing PTB. Compared to women with a metabolically healthy normal weight, those who are normal weight and overweight (including obese) with metabolically unwell had an increased chance of having PTB (adjusted OR: 1.33 and 1.62, respectively). Additionally, additive interaction analysis revealed a significant interaction between overweight and metabolic unhealthiness for PTB risk (RERI = 0.41, AP = 0.24, SI = 2.22). People who are overweight and metabolically unwell have a 0.41 relative excess risk (which accounts for 24%) of PTB, and their combined risk is 2.22 times higher than that of those who are exposed to either risk alone.

PTB risks are increased by metabolic abnormalities and overweight (including obese), and there are notable interaction effects between metabolic abnormalities and overweight (including obese) and PTB.