Abstract and Introduction
Pregnant women with coronavirus disease 2019 (COVID-19) are at increased risk for severe illness and might be at risk for preterm birth.[1–3] The full impact of infection with SARS-CoV-2, the virus that causes COVID-19, in pregnancy is unknown. Public health jurisdictions report information, including pregnancy status, on confirmed and probable COVID-19 cases to CDC through the National Notifiable Diseases Surveillance System.* Through the Surveillance for Emerging Threats to Mothers and Babies Network (SET-NET), 16 jurisdictions collected supplementary information on pregnancy and infant outcomes among 5,252 women with laboratory-confirmed SARS-CoV-2 infection reported during March 29–October 14, 2020. Among 3,912 live births with known gestational age, 12.9% were preterm (<37 weeks), higher than the reported 10.2% among the general U.S. population in 2019. Among 610 infants (21.3%) with reported SARS-CoV-2 test results, perinatal infection was infrequent (2.6%) and occurred primarily among infants whose mother had SARS-CoV-2 infection identified within 1 week of delivery. Because the majority of pregnant women with COVID-19 reported thus far experienced infection in the third trimester, ongoing surveillance is needed to assess effects of infections in early pregnancy, as well the longer-term outcomes of exposed infants. These findings can inform neonatal testing recommendations, clinical practice, and public health action and can be used by health care providers to counsel pregnant women on the risks of SARS-CoV-2 infection, including preterm births. Pregnant women and their household members should follow recommended infection prevention measures, including wearing a mask, social distancing, and frequent handwashing when going out or interacting with others or if there is a person within the household who has had exposure to COVID-19.†
SET-NET conducts longitudinal surveillance of pregnant women and their infants to understand the effects of emerging and reemerging threats.§ Supplementary pregnancy-related information is reported for women with SARS-CoV-2 infection (based on detection of SARS-CoV-2 in a clinical specimen by molecular amplification detection testing¶) during pregnancy through the day of delivery. As of October 14, 2020, 16 jurisdictions** have contributed data. Pregnancy status was ascertained through routine COVID-19 case surveillance or through matching of reported cases with other sources (e.g., vital records, administrative data) to identify or confirm pregnancy status. Data were abstracted using standard forms††; sources include routine public health investigations, vital records, laboratory reports, and medical records. Chi-squared tests were performed to test for statistically significant (p<0.05) differences in proportion of outcomes between women reported to have symptomatic infection and those reported to have asymptomatic infection using SAS (version 9.4; SAS Institute). This activity was reviewed by CDC and was conducted consistent with applicable federal law and CDC policy.§§
Jurisdictions reported 5,252 pregnant women with SARS-CoV-2 infection. Among these women, 309 (5.9%) were presumed to have ongoing pregnancies (no outcome reported and not past their estimated due date plus 90 days for reporting lag), and 501 (9.5%) did not have pregnancy outcomes reported and were either missing an estimated due date or presumed lost to follow-up. This report focuses on the 4,442 women with known pregnancy outcomes (84.6% of 5,252 women).
The median age of women was 28.9 years, and 46.0% were Hispanic or Latina (Hispanic) ethnicity (Table 1). At least one underlying medical condition was reported for 1,564 (45.1%) women, with prepregnancy obesity (body mass index ≥30 kg/m2) (35.1%) being the most commonly reported. Most (84.4%) women had infection identified in the third trimester (based on date of first positive test result or symptom onset). Symptom status was known for 2,691 (60.6%) women, 376 (14.0%) of whom were reported to be asymptomatic.
Among 4,527 fetuses and infants, the outcomes comprised 4,495 (99.3%) live births (including 79 sets of twins and one set of triplets), 12 (0.3%) pregnancy losses at <20 weeks' gestation, and 20 (0.4%) losses at ≥20 weeks' gestation (Table 2). Among 3,912 infants with reported gestational age, 506 (12.9%) were preterm, including 149 (3.8%) at <34 weeks and 357 (9.1%) at 34–37 weeks. Frequency of preterm birth did not differ by maternal symptom status (p = 0.62), including among women hospitalized at the time of infection (p = 0.81, Fisher's exact test). Among 3,486 (77.6%) live births with weight, gestational age, and sex reported, 198 (5.7%) were small for gestational age.¶¶ Twenty-eight (0.6%) infants were reported to have any birth defect; among 23 infants for whom timing of maternal SARS-CoV-2 infection during pregnancy was known, 17 (74%) were born to mothers with infection identified in the third trimester. Nine (0.2%) in-hospital neonatal deaths were reported. Among term infants (≥37 weeks' gestation), 9.3% were admitted to an intensive care unit (ICU); however, reason for admission was often missing.
Information on infant SARS-CoV-2 testing was reported from 13 jurisdictions; among 923 infants with information, 313 (33.9%) were not tested. Among 610 (21.3%) infants for whom molecular test results were reported, 16 (2.6%) results were positive (Table 3), including 14 for whom the timing of the mothers' infection during pregnancy was reported. The percent positivity was 4.3% (14 of 328) among infants born to women with documentation of infection identified ≤14 days before delivery and 0% (0 of 84) among those born to women with documentation of infection identified >14 days before delivery.
Eight of the infants with positive test results were born preterm (26–35 weeks); all were admitted to a neonatal ICU (NICU) without indications reported. Among the eight term infants with positive test results, one was admitted to a NICU for fever and receipt of supplemental oxygen, one had no information on NICU admission, and the remaining six were not admitted to a NICU. No neonatal immunoglobulin M or pregnancy-related specimen (e.g., placental tissue or amniotic fluid) testing was reported; thus, routes of transmission (in utero, peripartum, or postnatal) could not be assessed.
Morbidity and Mortality Weekly Report. 2020;69(44):1635-1640. © 2020 Centers for Disease Control and Prevention (CDC)