Covid-19 Moms at Higher Risk for Preterm Labor, Study Suggests

Pregnant women worldwide continue to worry about catching Covid-19 and passing the virus to their unborn baby. Each day we learn more, but much remains unknown about the coronavirus’s effects on pregnant women and babies.

The U.S. Centers for Disease Control and Prevention (CDC) provided an early release document on November 6th titled Birth and Infant Outcomes Following Laboratory-Confirmed SARS-CoV-2 Infection in Pregnancy. This paper verifies growing scientific consensus that pregnant women are at a higher risk of preterm labor if they acquire Covid-19 during pregnancy.

Based on current data, there is no evidence at this time indicating pregnant women are more at risk than the general public. We know that viral infections in pregnancy and postpartum can lead to poor outcomes in mothers and newborns.

Preterm labor most likely results from the severity of the maternal illness and is not caused by the virus itself.

Data so far indicates a pregnant woman who contracts Covid-19 has a low risk of passing the virus to her baby. The PRIORITY study(Pregnancy Coronavirus Outcomes Registry) showed that only 1.1% of infants contract the virus. The PRIORITY study also showed babies born to Covid-19 positive women do well. These babies showed no increase in key metrics such as low birth weight, difficulty breathing, apnea, or respiratory infections through the first eight weeks of life.

This new CDC paper adds to our current understanding of the effects of Covid-19 during pregnancy, showing an increase in preterm labor and providing more information on infant infection rates.

During pregnancy, women have a temporarily suppressed immune system and physiologic changes in their lung function. These changes put pregnant women at a higher risk of respiratory problems when they contract similar viruses, such as influenza or pneumonia. OB-GYNs, therefore, consider pregnant women to be an at-risk group for respiratory compromise if they contract Covid-19.

Additionally, preterm labor is a known risk when pregnant women contract viral illnesses such as MERS, SARS, and influenza. Preterm labor most likely results from the severity of the maternal illness and is not caused by the virus itself. In other words, preterm labor is not merely a result of contracting these viruses but rather dependent on the degree of illness that results.

Public health departments report Covid-19 pregnancy data to the CDC through the National Notifiable Diseases Surveillance System. Sixteen jurisdictions collected pregnancy and infant outcome data on 5,252 women with laboratory-confirmed SARS-CoV-2 infection.

This data was submitted to the CDC Surveillance for Emerging Threats to Mothers and Babies Network (SET-NET). SET-NET monitors the emerging and re-emerging threats to pregnant women and infants.

The authors studied 5,252 pregnancies. Three hundred nine women were still pregnant, so no delivery outcomes were available. Five hundred one pregnancies did not have a reported pregnancy outcome, or the gestational age at delivery was not available. This report analyzed the 4,442 women who had reported delivery outcomes and gestational age data.

Preterm labor rates increased in Covid-19 + Moms

Preterm labor increased by about 2% in pregnant women with confirmed Covid-19 infection.The gestational age was known in 3,912 cases. 12.9% of babies were born preterm compared to 10.2% in a national estimate of preterm labor rates. This finding suggests that pregnant women with SARS-CoV-2 infection might be at risk for preterm delivery, similar to other viral illnesses.

The authors are clear this data is preliminary and subject to change as scientists continue to learn more. These data studied mostly women with second and third-trimester infections and included a higher percentage of Non-Hispanic Black and Hispanic women.

Low rate of transmission to newborns

This report showed a low rate of neonatal transmission in line with previous reports. Among the 610 infants with SARS-Cov-2 testing results, only 2.6% of infants contracted the virus.

The neonatal infection rate was higher (4.3%) in babies born to women who tested positive for Covid-19 within 14 days of delivery.

Limitations of the study

The findings of this report are subject to at least six limitations.

1. Data collection was not standardized as interviews and medical record abstraction varied by jurisdiction.
2. The data are not nationally representative and included a higher number of Hispanic women.
3. Fetal death reporting data was dependent on linkages to existing data sources.
4. There was a lack of available information on women with first-trimester Covid-19 infections limiting long term surveillance.
5. The data did not ascertain participants’ baseline risk factors for preterm delivery.
6. Many of the infants had no SARS-CoV-2 RT-PCR results reported.

How does this report help doctors manage pregnancy?

This CDC report adds to the growing scientific literature to assist OB-GYNs in providing counsel and care to their pregnant patients. OB-GYNs can monitor pregnant women with Covid-19 for early signs and symptoms of preterm labor. Pediatricians can monitor babies born within 14 days of a maternal Covid-19 infection with extra caution.

Pregnant women with Covid-19 can also take comfort in knowing more evidence has emerged showing the risk of transmitting the virus to their baby is low.

Hospital staff can increase awareness of preterm labor risk in Covid-19 + women. This data also supports hospital policies supporting keeping mom and baby together after delivery.

How do pregnant women protect themself from Covid-19?

We all must do our part to prevent the spread of the virus. Pregnant women should follow the same global recommendations.

1. Wash your hands with soap and water for at least 20 seconds.
2. Use hand sanitizer containing at least 60% alcohol.
3. Avoid touching your face.
4. Practice social distancing.
5. Cover your mouth if you cough or sneeze.
6. Clean your cellphone and household surfaces.
7. Avoid travel.
8. Wear a mask when out in public.

CDC Morbidity and Mortality Weekly Report, “Birth and Infant Outcomes Following Laboratory-Confirmed SARS-CoV-2 Infection in Pregnancy — SET-NET, 16 Jurisdictions, March 29–October 14, 2020.