For every incidence of maternal mortality, maternal morbidity is thought to occur in another 50-100 individuals in the US. Multiple risk factors for severe maternal morbidity have been identified but counseling about specific risk in pregnancy remains difficult, particularly nulliparous individuals as prior obstetric history is one of the factors influencing risk for severe maternal morbidity.
To examine the association between sociodemographic and laboratory assessments in the first trimester and maternal morbidity in nulliparas.
This was a secondary analysis of a large, multicenter prospective observational cohort of nulliparas. The primary maternal outcome was a composite of hypertensive disorders of pregnancy (HDP), hemorrhage (transfusion, hemorrhage, hysterectomy, other surgery, readmission for bleeding), infection (endometritis, wound infection or dehiscence, pneumonia, sepsis, infection during L&D, readmission for infection through day 14), venous thromboembolic events (VTE) (deep venous thrombosis, or pulmonary embolus) or maternal death within 14 days of delivery. Sociodemographic and clinical factors were compared between people with and without maternal morbidity. Relative risk and 95% confidence interval for maternal morbidity was calculated using log-binomial regression, adjusted for baseline characteristics that had a significant independent relationship with maternal morbidity with a p-value <0.05.
Of 9,445 pregnant people in the analysis, 18.2% (n=1,716) experienced the composite maternal morbidity; the most common component was HDP (13.1%, n=1,244) followed by infection (4.43%, n=420), hemorrhage (2.27%, n= 215), VTE (0.12%, n=11) and death (0.01%, n=1). In a multivariable model, self-identified Black race, first trimester obesity, pregestational diabetes, chronic hypertension, and chronic kidney disease were significantly associated with the primary maternal outcome.
More than 1 in 6 nulliparas experienced the composite maternal morbidities. Maternal morbidity was associated with self-identified Black race, obesity and multiple pre-existing medical comorbidities.

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