ABSTRACT Objective Mortality in pregnancy due to coronavirus disease 2019 (COVID‐19) is a current health priority in developing countries. Identification of clinical and sociodemographic risk factors related to mortality in pregnant women with COVID‐19 could guide public policy and encourage such women to accept vaccination. We aimed to evaluate the association of comorbidities and socioeconomic determinants with COVID‐19‐related mortality and severe disease in pregnant women in Mexico. Methods This is an ongoing nationwide prospective cohort study that includes all pregnant women with a positive reverse‐transcription quantitative polymerase chain reaction result for severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) from the Mexican National Registry of Coronavirus. The primary outcome was maternal death due to COVID‐19. The association of comorbidities and socioeconomic characteristics with maternal death was explored using a log‐binomial regression model adjusted for possible confounders. Results There were 176 (1.35%) maternal deaths due to COVID‐19 among 13 062 consecutive SARS‐CoV‐2‐positive pregnant women. Maternal age, as a continuous (adjusted relative risk (aRR), 1.08 (95% CI, 1.05–1.10)) or categorical variable, was associated with maternal death due to COVID‐19; women aged 35–39 years (aRR, 3.16 (95% CI, 2.34–4.26)) or 40 years or older (aRR, 4.07 (95% CI, 2.65–6.25)) had a higher risk for mortality, as compared with those aged < 35 years. Other clinical risk factors associated with maternal mortality were pre‐existing diabetes (aRR, 2.66 (95% CI, 1.65–4.27)), chronic hypertension (aRR, 1.75 (95% CI, 1.02–3.00)) and obesity (aRR, 2.15 (95% CI, 1.46–3.17)). Very high social vulnerability (aRR, 1.88 (95% CI, 1.26–2.80)) and high social vulnerability (aRR, 1.49 (95% CI, 1.04–2.13)) were associated with an increased risk of maternal mortality, while very low social vulnerability was associated with a reduced risk (aRR, 0.47 (95% CI, 0.30–0.73)). Being poor or extremely poor were also risk factors for maternal mortality (aRR, 1.53 (95% CI, 1.09–2.15) and aRR, 1.83 (95% CI, 1.32–2.53), respectively). Conclusion This study, which comprises the largest prospective consecutive cohort of pregnant women with COVID‐19 to date, has confirmed that advanced maternal age, pre‐existing diabetes, chronic hypertension, obesity, high social vulnerability and low socioeconomic status are risk factors for COVID‐19‐related maternal mortality. © 2021 International Society of Ultrasound in Obstetrics and Gynecology.