Most medicines are safe to use during pregnancy and breastfeeding. However, some can cause considerable harm to your baby. This article looks at some of the things you may need to consider if you’re pregnant, thinking about becoming pregnant, or are breastfeeding.

Weighing up the benefits and risks

The list of medicines that can cause harm is not confined to prescription medicines. Non-prescription medicines, herbal and natural medicines, and vitamin and mineral supplements may also cause harm. For example, common pain relievers, such as ibuprofen (eg Nurofen), naproxen (eg Naprosyn) and aspirin can cause serious problems if used in the last three months of pregnancy.

Deciding to use any medicine involves weighing up its potential benefits and risks. During pregnancy and breastfeeding, this process is even more important because you need to consider the possibility of harming your baby. This may lead you or your doctor to make a different decision than you would make at other times. Also, the decisions may change depending on the stage of pregnancy, age of your baby, and your general health.

Medicines during pregnancy

Medicines that cause harm during pregnancy do so in three main ways. Some are transported across the
placenta, and interfere with the baby’s development. Others damage the placenta, and restrict the amount of nourishment delivered to the baby. Some bring on premature labour, resulting in the baby being born before its lungs and other organs are fully developed.

Generally, medicines are most likely to cause harm during the first three months when the baby’s organs are forming. After that time, there is less risk of harm. The exception is medicines that increase the chance of premature labour, which are most likely to be harmful in the last three months.

If you take medicine for a chronic condition, you

will usually be advised to continue treatment

while pregnant and breastfeeding.

Medicines when breastfeeding

Most of the medicines you use will pass into your breastmilk. In most cases, the concentrations will be so low that they won’t be harmful to your baby. However, a few medicines pass into the milk in high concentrations or are harmful to babies. Again, it is not only prescription medicines that can cause harm.

Staying well

Your baby’s normal development and growth depends on you being well. In some circumstances, using a medicine may be necessary to ensure that you stay as healthy as possible for your baby.

If you have a chronic condition

If you have a condition, such as asthma, diabetes, epilepsy or depression, you will usually be advised to continue treatment, because not treating the condition could be more harmful to you and your baby. For example, stopping treatment for diabetes increases the chance of miscarriage, stillbirth and some birth defects.

Seek advice from your GP, obstetrician, midwife or specialist about your medicines as early as possible in the pregnancy and preferably before you become pregnant. In many cases, you will not need to change your medication. However, the dose may be adjusted to allow for the additional work being done by your heart and kidneys. In some cases, you will be advised to change to another medicine for all or part of the time.

If you become unwell

Some illnesses can lead to problems for your baby if not treated. For example, an untreated urinary infection can develop into a kidney infection, which can lead to premature labour and a low birth weight baby. Similarly, illnesses related to pregnancy, such as severe morning sickness or high blood pressure, may cause problems for you and your baby if not treated. If you develop such an illness, your doctor may prescribe a medicine to treat the illness and prevent or minimise its effects on you and your baby.

The chances are that you won’t completely avoid the minor everyday illnesses that we all experience from time to time, such as colds, sore throats and headaches. You may decide not to take any medicines to relieve the symptoms of such illnesses because of your baby. However, if you do decide to use a medicine, first check that it is safe to use by

• talking to your doctor, pharmacist or midwife
• reading the packaging
• reading the Consumer Medicine Information (CMI) leaflet for the medicine
• ringing NPS Medicines Line on 1300 633 424.

Further information

• NPS Medicines Line (1300 633 424 or 1300 MEDICINE) provides free telephone advice about medicines, including the use of medicines during pregnancy and breastfeeding.
• healthdirect Australia webpage ‘Preparing for pregnancy (medicines and other drugs)’, which is part of the ‘Pregnancy, birth and baby’ website.
• Royal Women’s Hospital factsheet 'How common medications can affect your breast milk'.