There are key factors to be considered in making a risk assessment and a risk versus benefit decision about use of medicines in pregnancy.

The importance of the risk assessment

A different approach for medicines in pregnancy

The ideal scenario is to complete a risk assessment in advance of any pregnancy so that mitigating actions may be considered.

Assessing risk is particularly challenging during pregnancy because of the lack of information available.

Risk is assessed on an individual basis and so it is not possible to produce lists of ‘safe’ medicines or of medicines that must always be avoided in pregnancy.

Pregnancy is unique in that two individuals, the mother and fetus are exposed; with risks and benefits for each.

The maternal benefits and risks of a medicine in pregnancy are not necessarily the same as for non-pregnant women, because altered physiology and pharmacology may affect the efficacy of the treatment, or the risk of adverse effects.

Informing the risk v benefit decision

The decision to prescribe a medicine should always involve consideration of the risks and benefits for recipients.

Completing a risk assessment and using available evidence-based information relevant to that individual pregnancy, provides confidence in the advice provided, and enables an informed discussion with the woman about her treatment.

It is worth checking if a risk assessment has already been completed by the specialist team.

In certain cases it may be necessary to prescribe a suspected teratogen (a medicines known or suspected of increasing the risk of birth defects and development disorders), as the benefit may outweigh the risk due to, for example, the severity of the mother’s illness or stage of pregnancy.

Expert advice

Expert advice should be sought whenever there is any doubt about the safety of a medicine in pregnancy. If the information is not available on the SPS website, or your clinical scenario is complex, we would suggest you seek further advice from the Medicines Advice service.

Sources of risks in pregnancy

The sources of risk to the fetus include:

  • Background risk
  • Risks from the treatment i.e. the medicine may have teratogenic potential
  • Risks from failing to treat the mother, to both mother and fetus.

Background risk

There is a 2-3% background risk of congenital malformations (birth defects) for a normal healthy young mother. This background risk is irrespective of any medicines used during pregnancy.

NICE CKS explains the risk of miscarriage or having a baby with a birth defect may be increased by other factors including:

Increasing age

Pregnant women over age 35 have a higher chance of risk factors such as gestational diabetes and preeclampsia.

Poor maternal health

Pre-existing conditions such as high blood pressure and diabetes have a higher risk of miscarriage or other complications.

Conditions that occur during pregnancy like preeclampsia or gestational diabetes can be a risk for the pregnant woman or fetus if not treated.

Poor obstetric history

Poor outcomes or congenital malformations in previous pregnancies can sometimes mean there is a higher risk of these occurring in subsequent pregnancies.

Medicines and therapy

Some medicines are known or suspected to have the potential to increase the risk of birth defects and development disorders (teratogenic potential) when taken during pregnancy.

Medicines and chemicals are thought to account for approximately 4-6% of birth defects.

The benefit of treating the mother and maintaining good maternal health must be considered not only as a benefit to the mother but also as an important factor in supporting good fetal health and development.

Critical factors in assessing the risk

The questions you ask about the patient, indication, medicine(s) and the pregnancy, and the information you find, should provide information on the factors critical to assessing the risks associated with each individual pregnancy.

Critical factor considerations in making a risk assessment

Scientific Considerations

  • Does the available evidence for use of the medicine in pregnancy suggest an increased risk of congenital anomaly?
  • At what stage of pregnancy is exposure to the medicine associated with an increased risk?

Clinical Considerations

  • What is the medicine being used for (indication) and is it really needed?
  • Is the medicine being used to treat a minor or serious condition?
  • Are there treatment alternatives about which more is known or which pose a lower risk?
  • What is the risk to the mother if treatment was to be paused or stopped?
  • Will the medicine also be appropriate should the mother want to breastfeed?
  • Is there an alternative route / formulation which lowers risk? For example would topical eye drops and nasal spray be effective for hayfever symptoms in preference to an oral antihistamine.

Patient circumstances

  • At what stage of pregnancy is the patient?
  • Is the patient’s condition well controlled on the medicine?
  • Does the patient have concomitant illness?
  • Has the patient got an increased risk of adverse pregnancy outcome based on other risk factors such as her age or obstetric history?

Timing of the risk assessment

Before taking a medicine

If a woman is pregnant but is not yet using the medicine(s), the pharmacist or health care professional should provide advice on:

  • Choice or change of therapy
  • Potential risk of adverse effects or toxicity to the fetus (fetotoxicity)
  • Risk reduction e.g. stopping treatment if clinically possible or appropriate

After taking a medicine

Assessment after either inadvertent or deliberate medicine or chemical exposure during pregnancy, can require more careful, sensitive and nuanced advice. This may include the following actions:

  • Continue, or stop treatment or exposure.
  • Give reassurance
  • Prenatal diagnostic tests
  • Genetic counselling
  • In the case of acute poisoning – advice on treatment of the mother and potential risks to the mother and fetus
  • Consider therapeutic abortion – specialist advice must be sought before this is discussed or considered.

Update history

  1. Link to NICE CKS Miscarriage updated.
  1. Published

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