• Dr Peter Chew

Covid-19 vaccines, fertility, pregnancy and breastfeeding

H, a healthcare worker and mother of two had the first dose of Pfizer's vaccine. Her menstrual period which had been regular was delayed for over a week while awaiting for her second dose of the vaccine. She was much relieved when the blood test of the pregnancy hormone(B-hCG) was negative.


As the Singapore government is rolling out the vaccination program against covid-19, many women, like H, are concerned about the safety profiles of the vaccines with regards to fertility, pregnancy and breastfeeding.


In December 2020, an article was circulating in the social media which claimed that Pfizer’s vaccine could elicit antibodies that could damage the human placenta and cause infertility. This has caused much concerns of vaccine safety in pregnant mothers and in those women who are trying to conceive.


The claim was found to be false and was refuted subsequently by other laboratory and animal studies. Vaccines given to the rodents did not prevent pregnancy or had any harmful effects on the pups.


During the vaccine clinical trials in the UK and America where pregnant women were excluded, there was no significant difference in the rate of “Accidental pregnancies” –pregnancies occurring during the trial period--in the vaccinated groups compared with the control groups. The miscarriage rates were also similar between both groups. This suggested that the vaccines do not have any detrimental effects on fertility and early pregnancy.


Furthermore, women who are infected with covid-19 shortly before conceiving or early in pregnancy are no more likely to miscarry than their uninfected peers.


The following are the update of some of the key messages published by Royal College of Obstetricians and Gynaecologists(UK) on 7 May 2021.

  • The latest advice from the Joint Committee on Vaccination and Immunisation (JCVI) is that COVID-19 vaccines should be offered to pregnant women at the same time as the rest of the population, based on their age and clinical risk group. Women should discuss the benefits and risks of having the vaccine with their healthcare professional and reach a joint decision based on individual circumstances.

  • Women trying to become pregnant do not need to avoid pregnancy after vaccination and there is no evidence to suggest that COVID-19 vaccines will affect fertility.

  • You should not stop breastfeeding in order to be vaccinated against COVID-19.

However, until more local data are available, it is prudent to follow the advice by the Ministry of Health, Singapore which states:

  • Women who are planning a pregnancy are advised to consider deferring conception for 1 month after completing the second dose, out of an abundance of caution. This does not apply to male vaccine recipients.

  • There is currently not enough evidence to advise on the use of COVID-19 vaccines during pregnancy. It is recommended that pregnant women defer vaccination until more data become available. They may receive the COVID-19 vaccine after delivery.

  • Women who become pregnant after the first dose and before the second dose should not receive the second dose of vaccine, but should postpone it until after delivery.

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