Medicines in pregnancy: how UK advice works

Outside pregnancy a prescriber asks whether a medicine will help you. In pregnancy there are two people to think about, and the second cannot be asked or monitored directly. The NHS notes that most medicines reach the baby through the placenta, which is the reason pregnant women are told to check before taking anything, including products bought without a prescription.

The NHS Specialist Pharmacy Service describes the task as balancing maternal and fetal risks. Keeping the mother well is itself part of protecting the baby, so a serious untreated illness can carry more risk than a carefully chosen medicine. That is why the advice is rarely a flat list of banned drugs and more often a conversation about one person and one condition.

Prescribing guidance for pregnancy sets out a handful of principles. They are worth knowing because they explain why a prescriber may offer an older, well-established option rather than a newer one.

• Prescribe only when there is a clear benefit, after an individual risk-benefit assessment using current evidence.

• Use the lowest effective dose for the shortest time that works.

• Avoid medicines known to disrupt development of the baby.

• Prefer medicines with a long safety record over newly licensed ones, because the pregnancy data for new products is usually thin.

• Avoid taking several medicines together where possible.

• Avoid first-trimester exposure where a reasonable alternative exists, since the first 12 weeks carry the highest risk of structural effects.

The same guidance gives background figures that help keep medicine worries in proportion. Every pregnancy carries a 2 to 3 per cent chance of a birth defect and a 10 to 20 per cent chance of miscarriage whatever the woman takes, and medicines are thought to account for about 2.5 per cent of birth defects overall. Maternal age, long-term conditions such as diabetes or high blood pressure, alcohol, smoking and recreational drug use all add to risk in their own right.

Timing matters as well. Exposure in the first trimester is mainly a concern for structural problems, while later exposure is more likely to affect growth, organ function or the newborn after delivery. Some medicines that are acceptable early need review as pregnancy advances, and the reverse can also be true.

The MHRA has reiterated that paracetamol remains the first-choice treatment for pain and fever in pregnancy, to be used at the smallest effective amount for the shortest necessary period, and that leaving pain or fever untreated can itself be harmful to the baby. It also advises against switching to ibuprofen or other anti-inflammatory painkillers, which carry risks to the developing baby.

NHS pages on ibuprofen say it should be avoided in pregnancy unless a doctor or pharmacist advises otherwise, and the NHS page on anti-inflammatory painkillers more generally says they are not usually recommended in pregnancy. For coughs, colds, indigestion, hay fever and similar problems, a community pharmacist is the practical first stop because they can check the ingredients against your stage of pregnancy. Combination cold and flu products deserve particular care since they often contain several active ingredients.

People who take medicines for epilepsy, diabetes, asthma, mental health conditions, thyroid disease or high blood pressure are advised by the NHS to discuss their treatment before trying to conceive where possible. A planned review lets the prescriber change to the safest suitable option before pregnancy begins rather than during the vulnerable early weeks, when many people do not yet know they are pregnant.

If a pregnancy is discovered while you are taking a regular medicine, the NHS advice is to seek prompt advice and keep taking the medicine until that conversation has happened, unless a professional has told you otherwise. Abrupt withdrawal of some treatments can destabilise the condition and cause harm that outweighs the medicine risk.

The NHS warns that natural does not mean safe in pregnancy and that some remedies may contain harmful substances such as lead. Anyone seeing a complementary practitioner should say that they are pregnant and check that the practitioner is qualified. Herbal and supplement products are not tested for pregnancy in the way licensed medicines are, so the absence of a warning on the label is not reassurance.

BUMPS, short for Best Use of Medicines in Pregnancy, is run by the UK Teratology Information Service in partnership with the NHS. It provides leaflets written from the scientific material used by healthcare professionals, a searchable medicine list, short multilingual animations and a research portal. The NHS points to UKTIS for medicines that BUMPS does not yet cover.

The Specialist Pharmacy Service holds the professional guidance that midwives, pharmacists and prescribers draw on, including articles on risk assessment in pregnancy and treatment of common problems such as hay fever, haemorrhoids and pain. You can also report a suspected side effect through the MHRA Yellow Card scheme, which feeds into the safety picture over time.