Medical Drugs to Avoid

Many over-the-counter drugs can be harmful to your growing baby.

Many prescribed drugs or medicines can adversely affect a pregnancy. Drugs can pass through to the placenta and affect the growing foetus. Sometimes pregnancy can also affect the properties of a medication. As a general rule, it is best to avoid taking drugs three months before conceiving and during the first trimester. Always consult your doctor or health professional before taking medication during your pregnancy and when breastfeeding.

There are some medical conditions that require prescribed drugs to be taken during pregnancy and post partum. Such conditions may include:

  • diabetes
  • epilepsy
  • schizophrenia
  • some cases of depression

Often these drugs cannot be completely avoided, however it may be recommended that dosages altered by a health professional. Before you take any drug, check with your doctor that it is considered safe during pregnancy.

Over The Counter Drugs

Because drugs are available over the counter, this does not deem them pregnancy-friendly.

Drugs to be especially wary of during pregnancy:

  • Aspirin
  • Ibuprofen
  • Lithium
  • Carbimazole
  • Thyroxine
  • Warfarin and other anti-coagulants
  • Metformin
  • Vaccines for measles, rubella and yellow fever
  • Phenytoin
  • Tetracyclines
  • Chloroquin
  • Roaccutane
  • Anti-cancer drugs
  • Radiation from x-rays
  • Some antibiotics
  • Oral medicines for cystitis
  • Skin preparations containing vitamin A
  • If you are unsure, always ask your health professional.
  • Common Medicines & Prescribed Drugs
  • Analgesics

Low doses of paracetamol are usually considered safe during pregnancy (women at risk of pre-eclampsia use low-dose aspirin) though high doses for pain relief are considered unsafe. Indomethacin and other non-steroidal anti-inflammatory drugs should be avoided because they can affect your baby’s kidneys and cause bleeding.

Anti-Acne Tablets

Avoid all those based on vitamin A compounds (retinoic acid) which can cause birth defects. Certain antibiotics used to treat acne such as tetracycline and minocycline should not be taken as they affect your baby’s bones and discolour teeth.


No antibiotic should be prescribed without careful consideration of the alternatives, as antibiotics interfere with normal gut metabolism. They are of no use in viral infections and can seriously weaken the immune system especially used over prolonged periods of time.

Some are unsafe in pregnancy and have been linked to birth defects. Check with your health professional.

Anti-Coagulants (blood thinning agents)

Heparin is considered safe, as it is unable to pass through to the placenta. Prolonged use for more than six months can effect your bones increasing the risk of developing osteoporosis. Wafarin should not be taken in the first and last trimesters as it may cause bleeding in your baby.


Pregnant women on anti-convulsants have an increased likelihood of having a malformed baby. These drugs also increase the need for vitamin D. As an alternative, there is evidence to show that by working nutritionally with the levels of magnesium and manganese, in most cases the convulsions will cease.


These are known to decrease sperm count and mobility. Depression can be helped by balancing the trace mineral levels, particularly that of magnesium, manganese and B complex vitamins.

Anti-Hypertensives (Blood Pressure Tablets)

Methyldopa and labetatol have been used for many years and are considered quite safe. Nifedipine is commonly used but has been recently introduced to the market, thus there is limited understanding of possible adverse ramifications. Beta-blockers should be avoided and angiotensin converting enzyme inhibitors are considered dangerous in pregnancy.

Anti-Migraine Tablets

Many of these contain ergotamine-based substances that have the potential to contract the womb or cause miscarriage.

Anti-Thyroid Tablets

Drugs for an over-active thyroid, including carbimazole and propyithiouracil can cross the placenta and affect your baby’s thyroid function.


Can cross the placenta and cause Reye’s Syndrome, a rare brain and liver disorder in children.

Diuretics (Water Removal Tablets)

Ideally should not be used and any use should be supervised by a doctor.

Epilepsy Tablets

Although taking these drugs may pose a small risk to your baby, the risk to both you and your baby’s health if you stop taking them is potentially greater. Consult your medical professional. If you take these drugs, your levels of folic acid will be lower and therefore a folic acid supplement is recommended.


Avoid in the third trimester as it can delay the onset of labour and can have adverse affects on foetal development.


This is safe for your baby as it is thought that it is unable to cross through to the placenta. If you are diabetic, you need to maintain a good blood sugar level because glucose can cross the placenta and disrupt balances within your baby.


Thought to affect your baby’s thyroid and cause drowsiness in your newborn.

Oral Medicines For Cystitis

These have proven to be unsafe for both pregnant and lactating women.

Tranquilizers And Sleeping Pills

Benzodiazepines such as diazepam or temazepam should not be used at any time during pregnancy. They have been linked with visible malformations, functional problems and behavioural problems in children exposed to them while in the womb. They can affect the central nervous system development in early pregnancy.
In many cases, tranquilizers are taken to counteract the effects of over-stimulation from other social substances such as coffee.

Studies have also found that over-stimulation can arise from deficiencies in zinc, magnesium, manganese and B complex vitamins, which can easily be corrected when recognised.

If you are unsure ask your health professional.