COVID-19 can make pregnant women and their fetuses very sick. Recent studies have revealed that pregnant and recently pregnant women with COVID are at increased risk for severe illness when compared with non-pregnant people. Pregnant women with COVID are also at increased risk for preterm birth and might be at increased risk for other serious complications.
More and more evidence about the safety and effectiveness of COVID vaccination indicates that the benefits of vaccination outweigh any known or possible risks during or after pregnancy.
https://www.acog.org/clinical/clinical-guidance/practice-advisory/articles/2020/12/covid-19-vaccination-considerations-for-obstetric-gynecologic-care (The American College of Obstetricians and Gynecologists)
https://www.uchicagomedicine.org/forefront/coronavirus-disease-covid-19/mrna-covid-19-vaccine-pregnancy-breastfeeding (University of Chicago Medicine)