The objective of the study is to investigate if prepregnancy obesity plays a function as a mediator in the link between race and severe maternal morbidity.

Researchers examined a population-based retrospective cohort research in New York City that used birth records linked to hospital discharge data from 2010 to 2014. On a subset of the sample consisting of normal-weight and obese women, a multivariable logistic regression mediation model calculated the mediation effect of obesity in the association between maternal race–ethnicity and severe maternal morbidity, as well as the residual effect not mediated by obesity. A sensitivity analysis was out, eliminating instances of severe maternal morbidity caused by blood transfusion. 

Researchers found 15,158 incidences of severe maternal morbidity among 591,455 live births. Obese women had a greater risk of severe maternal morbidity than normal-weight women. Black women had nearly three times the rate of severe maternal morbidity as White women, and Latinas had nearly double the incidence of severe maternal morbidity as White women. Only among women with a normal or obese BMI was Black race-related with severe maternal morbidity (adjusted odds ratio [aOR] 3.02, 95% CI 2.88–3.17), although the obesity-mediated impact accounted for only 3.2% of the total association (aOR 1.03, 95% CI 1.02–1.05). Latina ethnicity was also linked to severe maternal morbidity (aOR 2.01, 95% CI 1.90–2.12), however, the obesity-mediated impact was minor, accounting for just 3.4% of the overall association (aOR 1.02, 95% CI 1.01–1.03). In a sensitivity analysis that excluded blood transfusions, severe maternal morbidity cases were shown to have a stronger mediation effect of obesity in the connection with Black race and Latina ethnicity (15.3% and 15.2% of the total association, respectively).

Pregnancy obesity, a controllable risk, appears to be a minor contributor to racial-ethnic inequalities in overall severe maternal morbidity, according to the data.