What We Do Know

What We Don't Know

During pregnancy women are generally on a higher level of alert regarding their health.

They are warned away from certain foods such as:

  • seafood high in mercury
  • raw, undercooked or contaminated seafood
  • undercooked meat, poultry and eggs
  • unpasteurized foods
  • unwashed fruits and vegetables
  • excess caffeine
  • herbal tea

They are also warned off drinking alcohol:

The Chief Medical Officers for the UK recommend that if you’re pregnant or planning to become pregnant, the safest approach is not to drink alcohol at all to keep risks to your baby to a minimum. Drinking in pregnancy can lead to long-term harm to the baby, with the more you drink, the greater the risk

They are also advised not to smoke:

Protecting your baby from tobacco smoke is one of the best things you can do to give your child a healthy start in life. It can be difficult to stop smoking, but it’s never too late to quit.

Every cigarette you smoke contains over 4,000 chemicals, so smoking when you are pregnant harms your unborn baby. Cigarettes can restrict the essential oxygen supply to your baby. As a result, their heart must beat harder every time you smoke.

When it comes to medicines, the NHS has the following to say:

Most medicines taken during pregnancy cross the placenta and reach the baby.

Before taking any medicine when you’re pregnant, including painkillers, check with your pharmacist, midwife or GP that it’s suitable.

When deciding whether to take a medicine during pregnancy, it’s important to find out about the possible effects of that medicine on your baby.

This is the case both for medicines prescribed by a doctor and for medicines you buy from a pharmacy or shop.

Which medicines are safe?

You can find out information on medicines in pregnancy on the bumps (best use of medicines in pregnancy) website.

They also have advice on what to do if you have already taken a medicine in pregnancy.

But it’s also important to never stop taking a medicine that’s been prescribed to keep you healthy without first checking with your doctor.

Stopping taking your medicine could be harmful to both you and your baby.

If you’re trying for a baby or are already pregnant, it’s important to always:

  • check with your doctor, midwife or pharmacist before taking any prescribed medicines or medicines that you have bought
  • make sure your doctor, dentist or another healthcare professional knows you’re pregnant before they prescribe anything or give you treatment
  • talk to your doctor immediately if you take regular medicine, ideally before you start trying for a baby or as soon as you find out you’re pregnant

If you cannot find information about a specific medicine on bumps, you can ask your doctor, midwife or pharmacist to contact the UK Teratology Information Service (UKTIS) for advice on your behalf.

And there is specific information regarding vaccines – and the COVID-19 vaccine in particular:

Some vaccines, such as the inactivated seasonal flu vaccine and the whooping cough vaccine, are recommended during pregnancy to protect the health of you and your baby. An inactivated vaccine does not contain a live version of the virus it is protecting against.

Some vaccines, such as the tetanus vaccine, are perfectly safe to have during pregnancy if necessary.

But it does depend on the type of vaccination. For example, the MMR and yellow fever vaccines have potential risks, and you need to discuss these with your midwife or doctor before deciding whether to have the vaccine.

Coronavirus (COVID-19) vaccine

If you’re pregnant, or think you might be, you can have the coronavirus (COVID-19) vaccine. You’ll be invited when your age group are offered it or earlier if you have a health condition or reason that means you’re eligible.

It’s preferable for you to have the Pfizer/BioNTech or Moderna vaccine. This is because they’ve been more widely used during pregnancy in other countries and have not caused any safety issues.

When you’re offered a vaccine, speak to your GP surgery to arrange an appointment. This is to make sure you go to a vaccination centre offering the Pfizer/BioNTech or Moderna vaccine.

A key factor in deciding if you are going to have a COVID-19 vaccination during your pregnancy, is getting an understanding of your risk from the disease.

Recent government and press announcements suggest that pregnant women are more at risk from COVID-19 than non-pregnant women. However they have not provided any empirical data to support this.

Meanwhile the NHS advises:

If you’re pregnant your chance of getting COVID-19 is not higher than anyone else and it’s very unlikely you’ll get seriously ill with it.

Pregnant women are in the moderate risk (clinically vulnerable) group as a precaution. This is because you can sometimes be more at risk from viruses like flu if you’re pregnant.

It’s not clear if this happens with COVID-19. But because it’s a new virus, it’s safer to include pregnant women in the moderate risk group.

Although it’s very rare for pregnant women to become seriously ill if they get COVID-19, it may be more likely later in pregnancy. If this happens, there’s a small chance your baby may be born early or you may be advised to give birth earlier than your due date.

While the chances of having a stillbirth are low, there is some emerging evidence that the risk may be higher if you have COVID-19 at the time of birth.

Given that pregnant women and their healthcare providers tend to apply the precautionary principle when dealing with any health concerns, it may be that what appears to be “pregnant woman at greater risk” is perhaps just that some pregnant women may have been admitted to hospital with COVID-19 as a precaution.


Past Problems With New Drugs & Pregnancy


Probably the most well known pharmaceutical tragedy was Thalidomide.  First marketed in 1956 it was available over the counter and recommended for morning sickness amongst other uses – despite having not been tested on pregnant women.  Its marketing in 46 countries led to the “biggest man‐made medical disaster ever,” resulting in more than 10,000 children born with a range of severe deformities, including missing and malformed limbs, as well as thousands of miscarriages. It is still on the market today though with special measures to prevent pregnancy risks

Accutane (Isotretinoin)
This Acne treatment was on the market for 27 years before it was finally recognised that it needed special measures to avoid any chance of pregnancy in recipients or their partners. This is due to the extremely high risk of severe birth defects including ear, eye and other face-related abnormalities to abnormal skull development. It is also known to cause Crohn’s Disease and Ulcerative Colitis as well as other intestinal problems but remains on the market.

Primodos was a hormone-based pregnancy test used in the 1960s and 70s. It was a super high dose of synthetic progesterone. The theory was that a pregnant woman would simply absorb the hormones whereas in a non-pregnant woman, it would trigger menstruation.  A concerned paediatrician first raised the alarm in 1967, citing high incidences of spina bifida but it would be another 11 years before the product was removed from the market.  Affected families are still fighting their legal battle for compensation.

DES (Diethylstibestrol)

DES was a synthetic oestrogen invented in 1938. First used as a treatment for menopause symptoms, it went on to be prescribed for miscarriage prevention. Despite being proven ineffective in 1953 it was still widely prescribed – due to manufacturers’ attempts to debunk the study – until 1971 when it was finally shown to cause miscarriages and birth defects. Continued investigations have since shown that daughters of DES recipients have a high incidence of womb deformity and that the effects of DES are being passed to the grandchildren of those to whom it was prescribed, with numerous birth defects and increased susceptibility to chronic disease. Only time will tell whether further generations will be affected.

Depakine/Depakote (valproate)

Pharma giant Sanofi, were last year indicted by French prosecutors on charges of manslaughter after it was shown that Depakine was responsible for up to 30,000 birth defects. On the market since 1967, the drug is used to treat epilepsy, migraines and bipolar disorder. But research found that when pregnant women took the drug, their children had an elevated risk — between 10 to 40 percent — of congenital malformations, autism and learning difficulties. Lawyers acting for families also discovered that health regulators were aware of the link between the drug and birth defects as early as 1983 and the link with autism by 2004, but failed to act to protect the public. Sanofi is currently working with GSK on a COVID-19 vaccine product.

Pregnant women were specifically excluded from the test groups during trials and the risk management document for the Pfizer/BioNTech vaccine which was issued on 29th April 2021 states that:

Module SIV. Populations Not Studied in Clinical Trials (page 72)

Women who are pregnant or breastfeeding

Reason for exclusion: To avoid use in a vulnerable population.

Is it considered to be included as missing information? Yes.

Rationale: It is not known if maternal vaccination with COVID-19 mRNA vaccine would have unexpected negative consequences to the embryo or foetus.

Exposure of Special Populations included or not in Clinical Trial
Development Programmes (page 73)

Pregnant Women

Available data on COVID-19 mRNA vaccine administered to pregnant women are insufficient to inform on vaccine-associated risks in pregnancy. Therefore, administration of Comirnaty in pregnancy should only be considered when the potential benefits outweigh any potential risks for the mother and foetus.

Participants 16 years of age and older

Through the cut-off date of 14 November 2020, there were 11 cases (11 events) originating from Study C4591001, and all were unique pregnancies.

Participants 12 to 15 years of age

Through the cut-off date of 13 March 2021, there were no cases of pregnancies.

Breastfeeding Women

Breastfeeding women were not included in the COVID-19 mRNA vaccine clinical development program.

Data are not available to assess the effects of COVID-19 mRNA vaccine on the breastfed infant or on milk production/excretion.

The developmental and health benefits of breastfeeding should be considered along with the mother’s clinical need for COVID-19 mRNA vaccine and any potential adverse effects on the breastfed newborn/infant/toddler from COVID19 mRNA vaccine or from the underlying maternal condition.

For preventive vaccines, the underlying maternal condition is susceptible to disease prevented by the vaccine.

Participants 16 years of age and older

Through the cut-off date of 14 November 2020, there were no CT cases
indicative of exposure during breastfeeding.

Participants 12 to 15 years of age

Through the cut-off date of 13 March 2021, there were no CT cases indicative
of exposure during breastfeeding.

Presentation of the Missing Information (page 85)

Use in pregnancy and while breast feeding

Evidence source:
The safety profile of the vaccine is not known in pregnant or breastfeeding women due to their exclusion from the pivotal clinical study. There may be pregnant women who choose to be vaccinated despite the lack of safety data. It will be important to follow these women for pregnancy and birth outcomes. The timing of vaccination in a pregnant woman and the subsequent immune response may have varying favourable or unfavourable impacts on the embryo/foetus. The clinical consequences of SARS-CoV-2 infection to the woman and foetus during pregnancy is not yet fully understood and the pregnant woman’s baseline health status may affect both the clinical course of her pregnancy and the severity of COVID-19. These factors and the extent to which the pregnant woman may be at risk of exposure to SARS-CoV-2 will influence the benefit risk considerations for use of the vaccine.

Population in need of further characterisation:
The lack of data will be communicated in product labelling; a clinical study of the safety and immunogenicity of COVID-19 mRNA vaccine in pregnant women, is planned.

Since the release of this risk management document, there has still not been a clinical study conducted of the risks and/or benefits of COVID-19 vaccination for pregnant women and their unborn babies.  On 3rd August 2021, the UK Government announced a new clinical study of COVID-19 vaccination during pregnancy, but this is merely focused on determining the optimum gap between the first and second doses and not on the safety of the vaccine itself.

The UK Government recommendation that pregnant women be vaccinated is justified as follows:  

Following 130,000 pregnant women being vaccinated in the US and no safety concerns being raised, the Pfizer/BioNTech and Moderna vaccines were recommended by the independent experts at the Joint Committee on Vaccination and Immunisation (JCVI) for pregnant women in the UK. Almost 52,000 pregnant women in England have now been vaccinated – similarly, with no safety concerns reported.

Data published last week by NHS England and the University of Oxford also shows no pregnant women who have had both doses of a vaccine have been admitted to hospital with COVID-19. Only 3 have been admitted after having their first dose, meaning 98% of those admitted to hospital have not received a jab.

Yet if we consult the VAERS database, the USA system for recording adverse reactions to vaccines (as at 9th August 2021), we find:

And this is just a quick search using the word “Premature”.  It is not an exhaustive list of the myriad of clinical terms associated with pregnancy and breastfeeding complications or reactions. 

While some may argue that this number is tiny compared to the 130,000 women vaccinated, it is still not zero and “no safety concerns raised” is not the same as “no possible adverse reactions reported”.

Equally, the UK’s MHRA Yellow Card system shows (as at 28th July 2021):

Reaction AstraZeneca Pfizer Moderna Unspecified
Congenital Disorders 85 51 3 0
Spontaneous Abortions (miscarriage), Foetal Death, Still birth 177 220 22 1
Other Pregnancy Related Reactions 127 110 15 1
Breast related reactions 740 669 53 3
Lactation disorders 32 30 3 0
Ovarian disorders 115 81 11 2
Uterine disorders 175 117 17 0
Other Reproductive disorders 14794 13656 1745 94

What We Do Know

What We Don't Know


The laws and principles of informed consent require that a patient be fully informed of all risks prior to treatment being given. 

Our aim with this article is not to be “anti-vax” but rather to provide access to some of the missing information to help women and their partners be better informed and consider all aspects of COVID-19 vaccination. Because ultimately it is for individual mothers (and fathers) to weigh the risks they are willing to take, and not for politicians to omit information on reactions because they do not consider them significant. 

To further help your decision making, you may wish to download our PDF “Questions to Get Answered By a Healthcare Professional
BEFORE Giving Consent for a COVID-19 Vaccine”

Update - March 2023

We strongly recommend that anyone considering a COVID-19 vaccine while pregnant – or indeed hoping to get pregnant – read this excellent article which has analysis of the US VAERS statistics relating to pregnancy, stillbirth and birth defects.  We see a similar picture in the UK’s Yellow Card data.

Essential Context for Understanding this report

These reports contain a complete listing of all suspected adverse reactions that have been reported to the MHRA via the Yellow Card scheme for COVID-19 vaccines. This includes all reports received from healthcare professionals, members of the public, and pharmaceutical companies.

This information does not represent an overview of the potential side effects associated with the vaccines. A list of the recognised adverse effects of the COVID-19 vaccines is provided in the information for healthcare professionals and the recipient information here. Conclusions on the safety and risks of the vaccines cannot be made on the data shown in the report alone. When viewing the report, you should remember that:

  • Reporters are asked to submit Yellow Card reports even if they only have a suspicion that the vaccine may have caused the adverse reaction. The existence of an adverse reaction report does not necessarily mean that the vaccine has caused the reaction.

  • It may be difficult to tell the difference between something that has occurred naturally and an adverse reaction. Sometimes reactions can be part of the condition being treated rather than being caused by the vaccine.

  • Many factors have to be considered when assessing whether a vaccine has caused a reported adverse reaction. When monitoring the safety of medicines and vaccines, MHRA staff carry out careful analysis of these factors.

  • It is not possible to compare the safety of different vaccines by comparing the numbers presented in the vaccine reports. Reporting rates can be influenced by many factors including the seriousness of the adverse reactions, their ease of recognition and the extent of use of a particular vaccine. Reporting can also be stimulated by promotion and publicity about a product.

For a vaccine to be considered safe, the expected benefits will be greater than the risk of having harmful reactions. It is important to note that most people receive vaccinations without having any serious side effects.

Risks and benefits of medicines

For a medicine to be considered safe, the expected benefits of the medicine will be greater than the risk of suffering harmful reactions. It is important to note that most people take medicines without suffering any serious side effects.

All medicines can cause reactions. The patient information leaflet accompanying the medicine, or available from your pharmacist, lists the known side effects associated with the medicine. Healthcare professionals such as doctors and pharmacists can also provide this information. Information on side effects of medicines can be found on the NHS website.

Monitoring the safety of medicines and vaccines

Information collected through the Yellow Card scheme is an important tool in helping the MHRA and CHM monitor the safety of medicines. Yellow Card reports of suspected adverse reactions are evaluated, together with additional sources of evidence such as worldwide literature, in order to identify previously unidentified hazards or side effects.

If a new side effect is identified, information is carefully considered in context of the overall side effect profile for the medicine or vaccine, and how it compares with other medicines used to treat the same condition.

The MHRA will take action, if necessary, to ensure that the product is used in a way that minimises risk, while maximising patient benefit. Such changes may include, for example, restricting the indication, or special warnings and precautions. Rarely, a drug may need to be withdrawn from the market if the risk of side effects is considered to outweigh the benefits of treatment. Please see our How we monitor the safety of medicines section for further information.

Use of Yellow Card data for publication

If you wish to copy or circulate the information contained within a report to anyone else, please ensure that a copy of these guidelines is also provided.

The MHRA and CHM encourage the use of data from the Yellow Card scheme in research and for publication, but wish to ensure that the limitations of interpretation of the data are made clear.

If you propose to publish information based on Yellow Card data, the MHRA is most willing to provide advice on how the Yellow Card information might be best used and presented. The MHRA is also willing to provide feedback on manuscripts prior to publication. Please write to the Deputy Director, Safety and Surveillance Group by email.