Preliminary findings from a study on the initial safety of mRNA vaccines in pregnant persons published in April 2021 did not show obvious safety signals with respect to pregnancy or neonatal outcomes associated with Covid-19 vaccination in the third trimester of pregnancy. The study authors noted that more longitudinal follow-up, including follow-up of large numbers of vaccinated pregnant persons early on in the pregnancy and in the preconception period was needed to inform maternal, pregnancy and infant outcomes. This study involved pregnant participants who received mRNA COVID-19 vaccines between December 14, 2020 and February 28, 2021 and participated in the v-safe health checker or the v-safe pregnancy registry. In addition to v-safe data, the study authors also analyzed data from VAERS.
Specific study findings were:
A prospective cohort study published in late March 2021 looked at antibody levels in 131 mRNA vaccine recipients (84 pregnant, 31 lactating, and 16 nonpregnant). The study found that pregnant and lactating women elicited comparable vaccine antibody immune responses to non-pregnant controls, and generated higher antibody titers than those observed following COVID-19 infection in pregnancy. Vaccine-generated antibodies were present in umbilical cord blood and breastmilk after maternal vaccination.
Both ACIP and the American College of Obstetrics and Gynecology (ACOG) recommends pregnant women be offered counseling to make an informed decision regarding the vaccine. These conversations may include discussion on likelihood of exposure to COVID-19, potential risks of COVID-19 to them and the baby, and lack of data about the vaccine in pregnancy.
Observational data demonstrate that, while the chances for these severe health effects are low, pregnant people with COVID-19 have an increased risk of severe illness, including illness that results in ICU admission, mechanical ventilation, and death compared with non-pregnant women of reproductive age. Pregnant people with COVID-19 might be at increased risk of adverse pregnancy outcomes, such as preterm birth, compared with pregnant women without COVID-19.
Limited data are currently available from animal developmental and reproductive toxicity studies. No safety concerns were demonstrated in rats that received Moderna COVID-19 vaccine before or during pregnancy; studies of the Pfizer-BioNTech vaccine are ongoing.
Conception Between Doses
In addition, the American Society of Reproductive Medicine recommends that patients who conceive in the window between the first and second dose of the vaccine should be offered the second dose of the vaccine at the appropriate interval.
According to the American Society of Reproductive Medicine, while COVID-19 vaccination can cause fever in some patients, this risk should not be a concern when deciding whether to vaccinate a pregnant individual or a patient desiring pregnancy. While fever in pregnancy (particularly the 1st trimester) has been associated with an increased risk of neural tube defects, a recent study demonstrated the association no longer remained significant if the patient is taking >400 mcg of folic acid daily. Another large Danish cohort study did not demonstrate any increased risk of congenital anomalies of those who reported fever in the first trimester. Additionally, the most common symptom of COVID-19 infection itself is fever (83-99% of affected patients). Patients who experience fever following vaccination should take an antipyretic medication, like acetaminophen.
Johnson and Johnson
Available data on Janssen COVID-19 Vaccine administered to pregnant women are insufficient to inform vaccine-associated risks in pregnancy. We are awaiting recommendations from professional societies.
There are no data on the safety of COVID-19 vaccines in lactating women or on the effects of mRNA vaccines on the breastfed infant or on milk production/excretion. mRNA vaccines are not thought to be a risk to the breastfeeding infant. According to ACOG, COVID-19 vaccines should be offered to lactating individuals similar to non-lactating individuals when they meet the criteria for receipt of the vaccine based on prioritization groups outlined by the ACIP.
Johnson and Johnson
Data are not available to assess the effects of Janssen COVID-19 vaccine on the breastfed infant or on milk production/excretion. We are awaiting recommendations from professional societies.
Of note, the adenovirus vector platform used in the Janssen COVID-19 vaccine has also been used for other Janssen vaccine development programs that have included pregnant people vaccinated during any trimester, including in a large-scale Ebola vaccination trial. No adverse pregnancy-related outcomes—including infant outcomes—were determined to be related to the vaccine in these trials.
Updated: May 5, 2021