delay COVID-19 vaccination until late pregnancy.
More than 98% of the women who had received the vaccines did so during the second or third trimester of pregnancy. About 1.7% received their vaccines in the first trimester. A majority were vaccinated with the shots developed by Pfizer or Moderna.
Preterm birth, in which babies are delivered earlier than 37 weeks, and being small for gestational age have been associated with a higher risk for infant death and disability.
The trimester when the vaccination was received and the number of COVID-19 vaccine doses received were also not associated with increased risk of preterm birth or with the infant being small for gestational age, the study found.
What the study shows
The researchers analyzed antibodies in 1,359 pregnant women who had been vaccinated for COVID-19 during or up to six weeks before pregnancy and who gave birth after at least 34 weeks’ gestation.
Antibodies were generally detectable at delivery in both maternal and cord blood among all the fully vaccinated women.
If you have no history of SARS-CoV-2: Among women with no history of SARS-CoV-2 infection who received the two-dose Pfizer or Moderna mRNA vaccine, antibody levels at delivery were lowest among those who were vaccinated before pregnancy or in their first trimester. Levels were highest after third-trimester vaccination, but the difference wasn’t large.
If you received the J&J booster: There was no significant difference in antibody levels by the timing of vaccination in women who received the Johnson & Johnson single-dose vaccine, though few in the study had received that shot.
If you had a prior history of COVID: Among vaccinated women who had a prior history of COVID-19 infection, antibody levels at delivery in maternal and cord blood were moderately higher on average. They also showed even less of a decline with earlier vaccination timing.
On average, the 20 women who reported having a booster dose in their third trimester had