Last reviewed: January 21, 2022
On this page:
- Epidemiology & Outcomes of COVID-19 During Pregnancy
- Fetal Outcomes & Vaccine Safety
- Vaccination During Pregnancy & Breastfeeding
The following is a curated review of key information and literature about this topic. It is not comprehensive of all data related to this subject.
Pregnant people are vulnerable to severe viral infections, and this association has been strongly demonstrated during COVID-19 pandemic. On average, pregnant people suffer more serious disease due to SARS-CoV-2 than comparable nonpregnant people, and this results in elevated risk to their unborn children. Although COVID-19 vaccinations are safe, effective and recommended by CDC and major pregnancy experts, vaccine uptake among pregnant people in the U.S. remains low.
This low vaccination rate is of concern given the spread of highly transmissible variants because unvaccinated pregnant people and their babies remain at higher risk for serious COVID-19 outcomes. National data and guidance suggest a critical need for health care personnel to recommend COVID-19 vaccination to all pregnant people to significantly reduce their personal risk of severe COVID-19 and risk to their unborn children.
As of January 2021, there have been >150,000 documented COVID-19 cases in U.S. pregnant people, with >25,000 hospitalizations, and >250 parental deaths (CDC, January 2021). CDC data indicated that 97% of hospitalized pregnant people through fall 2021 were unvaccinated (CDC, September 2021). Deaths in pregnant people escalated during the U.S. Delta variant wave, with 22 deaths in August 2021, alone. The impact of the highly transmissible Omicron variant is not yet known.
The risk of developing severe COVID-19 is significantly higher in pregnant people than in similar nonpregnant adults, including two-fold higher risks of mechanical ventilation, critical illness and death (Allotey, September 2020). This is particularly true for people of older age (≥35) and with any medical condition such as obesity, hypertension or diabetes. An early multinational study indicated nearly two-fold higher risk of preeclampsia, five-fold higher risk of ICU admission and 22-fold higher risk of death among pregnant people with COVID-19 as compared to those who were not infected (Villar, April 2021). Large-scale U.S. studies confirmed that in unvaccinated people, pregnancy status confers more than a two-fold increased risk for ICU admission and 70% higher risk of death due to COVID-19 (Zambrano, November 2020).
Vaccination, as in the general population, appears to significantly reduce severe illness and death during pregnancy. One U.S. series reported zero deaths in fully vaccinated pregnant people versus 15 COVID-19-associated deaths (14 unvaccinated, 1 partially vaccinated) among 1,637 total infections (Kasehagen, November 2021). Real-world data also indicate that two-dose mRNA vaccines are >90% effective in preventing infection and severe COVID-19 illness among pregnant people (Dagan, September 2021; Goldshtein, July 2021). A separate Scottish study of nearly 5,000 pregnant people found that 77% of all infections during pregnancy were in unvaccinated women, including 91% of infections associated with hospitalization and 98% of critical care admissions (102 of 104) (Stock, January 2022).
Although the Omicron variant leads to significant antibody evasion (Carreño, December 2021) and reduced vaccine effectiveness, non-peer-reviewed data indicate that pregnant people may maintain a degree of antibody recognition after two-dose mRNA vaccination (Bartsch, January 2022 - preprint, not peer-reviewed). Immune response likely improves with booster dosing, which the CDC recommends irrespective of pregnancy status (CDC, December 2021).
As with other severe viral illnesses, fetal outcomes appear worse if a pregnant person develops COVID-19. Among >1 million U.S. delivery hospitalizations, the risk of stillbirth (fetal death at ≥20 weeks gestation) was nearly two-fold higher in pregnant people with COVID-19 and increased to four-fold higher during the Delta variant wave (DeSisto, November 2021). A recent study of >2,000 babies born to people with COVID-19 confirmed a doubling of premature deliveries in unvaccinated versus vaccinated pregnant people, with vaccination reducing risk to the level of mothers who did not have COVID-19 (Stock, January 2022). All 14 perinatal deaths following parental SARS-CoV-2 infection were among unvaccinated pregnant people (nearly three-fold higher than expected rates). This supported earlier series in which the risk of preterm birth was also 1.5- to 2-fold higher if the parent had COVID-19 (especially if symptomatic), and overall severe neonatal outcome was increased by 2.7-fold (Villar, April 2021). Notably, 13% of neonates in this latter series also tested positive for SARS-CoV-2 if their parent tested positive, particularly those delivered by caesarian section.
COVID-19 vaccines, in contrast, have not been shown to cause worse fetal outcomes. The CDC Vaccine Safety Datalink examined >100,000 U.S. pregnancies, of which >13,000 (12.5%) ended in spontaneous abortion (miscarriage). There was no association between receipt of any COVID-19 vaccine and higher risk of spontaneous abortion (adjusted OR, 1.02 [95% CI, 0.96-1.08]) (Kharbanda, September 2021). Additional VSD analysis of over 10,000 pregnancies found that vaccination, predominately in the second and third trimester with mRNA vaccines, was not associated with preterm labor (adjusted HR, 0.91 [0.82-1.01], p=0.06) or small-for-gestational age at birth (adjusted HR, 0.95 [0.81-1.03], p=0.24) (Lipkind, January 2021). The national anonymized vaccine registry V-safe has recorded vaccination for more than 180,000 pregnant people and is actively following more than 8,000 vaccinated people for adverse event monitoring (CDC).
Given serious illness in pregnant people and demonstrated safety of the COVID-19 vaccines, major societal and governmental agencies all recommend vaccination for pregnant people. In summer 2021, the Society for Maternal-Fetal Medicine and partner organizations explicitly recommended vaccination during pregnancy and lactation (SMFM, July 2021). In fall 2021, CDC reiterated strong recommendation for vaccination before or during pregnancy to protect both parent and child, though vaccination rates are lagging. Only 31% of pregnant people were fully vaccinated as of September 2021, including only 16% of non-Hispanic Black pregnant people (CDC Health Alert Network).
Importantly, multiple studies indicate COVID-19 vaccines are highly immunogenic in pregnant people and may lead to passive antibody transfer to the fetus (Gray, March 2021; Collier, May 2021). High anti-spike antibody levels and virus neutralization are seen in pregnant people after mRNA vaccination, similar to levels in nonpregnant people and much higher than those of previously infected women. Additionally, protective antibodies are present in cord blood and breast milk, indicating they may be passively transmitted to the fetus and neonate. There has been no signal for worsened vaccine reactogenicity in pregnant people versus other similar populations.
Current recommendations that strongly support vaccination in this population include:
- CDC, which recommends COVID-19 vaccination for all people 5 years and older, including people who are pregnant, breastfeeding, trying to get pregnant now, or might become pregnant in the future.
- The American College of Obstetrics and Gynecologists, which recommends that all eligible people, including pregnant and lactating individuals, receive a COVID-19 vaccine or vaccine series.
- The Society for Maternal-Fetal Medicine, which recommends that COVID-19 vaccines be offered to pregnant and lactating individuals.