Epidemiological trends of SARS-CoV-2 infections during pregnancy in Chicago
Authors: Reddy Kavya , Akel Mary J , Sunderraj Ashwin , Redondo Ramon Lorenzo , Goldstein Jeffery , Mithal Leena B 
Published: October 2024

Abstract

Background
The epidemiology of SARS-CoV-2 has varied significantly across age groups, specifically children. Immune and physiologic changes in pregnancy can lead to increased susceptibility to infection. Pregnant people were at increased risk of severe COVID-19 infections and obstetric complications, particularly before vaccine availability. We investigated epidemiologic trends of SARS-CoV-2 cases in pregnant people over time compared to trends in the general population and various age subgroups. We hypothesized that rates of SAR-CoV-2 infection in pregnant people may show a similar pattern to children rather than nonpregnant adults.

Methods
Cases of pregnant persons with SARS-CoV-2 infection who delivered at Prentice Women’s Hospital (Chicago, IL) were identified through the electronic medical record (March 2020-November 2022). Prentice has ~12,000 births annually. Clinical data collection for SARS-CoV-2 cases included the date of positive test, maternal demographics, vaccination status, severity, and latency (days between SARS-CoV-2 infection and delivery). SARS-CoV-2 cases rates in Chicago (cases/100,000; total; age 0-17 years, ≥18 years) were obtained from the Chicago Department of Public Health. Monthly average SARS-CoV-2 rates were calculated to visualize trends over the study period using Microsoft Excel.

Results
A total of 3,474 SARS-CoV-2 cases in pregnancy were included in the final dataset; 497 cases were excluded from analyses due to incomplete data to pinpoint timing of infection. The median maternal age was 33 years (IQR 30-36) with a median latency of 72 days (IQR 22-143.75). Over half (2206) of pregnant persons received COVID-19 vaccination. In terms of timing, 514 people (15%) tested positive during their 1st trimester, 1017 (29%) in 2nd trimester, and 1943 (56%) in 3rd trimester. The trends of SARS-CoV-2 cases over time among pregnant persons coincide closely with trends among children in Chicago rather than adults [Figure 1]. A steep spike and higher SARS-CoV-2 rates were observed in pregnancy during the initial Omicron variant surge (December 2021-January 2022) and in April-July 2022, during which children also led case rates. Earlier in the pandemic, pregnant people and children were less affected than non-pregnant adults.

Conclusion
We observed an interesting trend of SARS-CoV-2 cases among pregnant persons aligning with rates in children in Chicago rather than adults. Possible explanations include: 1) pregnant people exercising an abundance of caution prior to vaccine availability and knowledge about COVID-19 in pregnancy and 2) epidemiologic link of maternal exposure to children. This information may inform public health strategies and effective precautions in future epidemics/pandemics to keep patients safe during pregnancy.

Figure 1. Cases of SARS-CoV-2 in age and pregnancy subgroups in Chicago. Blue bars represent SARS-CoV-2 positive cases among pregnant people who later delivered at Prentice Women’s Hospital [left y-axis] March 2020-November 2022. Colored lines represent case rate (cases/100,000) in Chicago according to Chicago Department of Public Health data (yellow = total, purple = adults ≥18 years, red = children 0-17 years) [right y-axis].