Pregnancy - medication, drugs and alcohol

Many women take some kind of drug, substance or medication during pregnancy without realizing it could harm their baby. Stopping can be difficult, sometimes because of past life experiences, ongoing health problems or social stress such as family violence or homelessness.

Drugs and medicines taken during pregnancy can cross the placenta and affect the developing baby. Possible effects include the baby withdrawing from substances after birth, low birth weight, premature birth, miscarriage and stillbirth.

Tell your doctor or midwife everything you take#

It helps doctors and midwives to have a complete list of everything you take, or have recently taken, so they can best support you and your baby. This includes:

• Prescription medicines.
• Over-the-counter medicines.
• Complementary medicines, such as herbal remedies, vitamins or other nutrition supplements.
• Opioid-based pain medicines, such as those containing codeine.
• Alcohol, tobacco and caffeine.
• Illegal or non-prescribed drugs.
• Any medication prescribed for someone else.

Tell your doctor or midwife if you smoke, drink alcohol or use other drugs, even occasionally or socially. This helps them care for you and your baby.

How harm can happen#

How much risk a substance poses depends on several things:

• The type of drug or medicine and how it is taken.
• The size of the dose and how often it is used.
• Whether it is used alone or combined with other substances.
• The individual baby’s response.
• The gestational age of the baby.
• Other factors, such as the mother’s physical and mental health, diet and social stress.

Substances can harm a baby by interfering with normal growth and development, affecting the growth of the baby’s organs, affecting the placenta (the baby’s source of food and nutrients), increasing the risk of pre-term birth, or causing the baby to withdraw from substances and need treatment after birth.

It is worth knowing that the risk of a birth abnormality for any baby is about 4 per cent, regardless of what happens during pregnancy. This means even a woman who strictly avoids drugs and medicines may still have a baby with a birth abnormality.

Medicines and birth abnormalities#

Most medicines are not harmful to a developing baby. However, some can interfere with normal development of the fetus — these are described as “teratogenic.” Drugs and drug groups that may cause birth abnormalities include:

• ACE (angiotensin converting enzyme) inhibitors and angiotensin II antagonists, used for high blood pressure or heart failure.
• Isotretinoin (an acne drug) and high doses of vitamin A.
• The hormone diethylstilbestrol (DES) and male hormones.
• Alcohol, cocaine and lithium.
• Thalidomide and the blood-thinning drug warfarin.
• Some antibiotics, anticonvulsants, cancer-fighting medicines, thyroid medicines and drugs for certain rheumatic conditions.

This list is not complete. The effects of some illegal drugs, such as cannabis or methamphetamines, are not well understood because there have been few medical studies.

Pregnancy risk classification for medicines#

In many countries, medicines used in pregnancy are given a risk category based on their safety information. These categories apply only to recommended doses. A common system uses the following classes:

• A — taken by a large number of pregnant women with no proven increase in birth defects.
• B — taken by only a limited number of pregnant women. Human data is lacking, so these are sub-categorized using animal data:
  • B1 — animal studies show no increased risk.
  • B2 — animal studies are limited but show no apparent increased risk.
  • B3 — animal studies show an increased risk, but it is unclear whether this applies to humans.
• C — may harm the fetus through their effects, without causing birth defects; these effects may be reversible.
• D — have caused, or may cause, birth defects, though the health benefit may sometimes outweigh the risk.
• X — have a high risk of birth defects and should not be used during pregnancy.

See your doctor or pharmacist for further explanation.

Medicines that may be necessary during pregnancy#

Good health in the mother is vital for the healthy development of her baby. Women with pre-existing conditions — such as asthma, epilepsy, high blood pressure, thyroid conditions, diabetes or mental health conditions — often need to continue treatment during pregnancy. Sometimes a medicine can carry some risk to the baby, but stopping it could be more dangerous for both mother and baby. For example:

• If a woman with asthma stops her medication, her baby’s growth may slow.
• If a woman with epilepsy stops anti-epileptic medication, she risks seizures and complications for herself and her baby.
• Poorly managed diabetes increases the health risk to the baby.

In some cases your doctor can prescribe a similar medicine considered safer in pregnancy. Do not stop or change the dose of a prescribed medicine without your doctor’s knowledge and consent, and discuss any concerns with your doctor or midwife.

Smoking, caffeine and alcohol#

Some women may not realize that smoking, alcohol and caffeine during pregnancy can harm their baby.

• Smoking increases the risk of miscarriage and stillbirth. Babies have a greater risk of low birth weight, prematurity and sudden unexpected death in infancy (SUDI).
• Caffeine — heavy use may be associated with miscarriage and low birth weight.
• Alcohol has been linked to miscarriage, babies who are small for their gestational age, and intellectual impairment (fetal alcohol syndrome).

No completely safe level of alcohol in pregnancy is known, so not drinking is the safest option. The risk of harm is highest with frequent, heavy drinking, and is likely to be low if a woman drank only small amounts before she knew she was pregnant. The level of risk to an individual baby is hard to predict. The amount of alcohol in a “standard drink” is defined differently in different countries.

Illegal drugs and pregnancy#

Knowledge of the effects of illegal drugs in pregnancy is limited, but substances with some known effects include:

• Methamphetamines and amphetamines — increased risk of low birth weight, birth defects and premature birth.
• Cannabis — increased risk of growth restriction, sleep problems and behavioural problems later in life.
• Cocaine — increased risk of miscarriage, pre-term birth, growth restriction, stillbirth and birth defects (of the brain, heart, genitals and urinary system).
• Heroin — increased risk of low birth weight, prematurity, fetal distress, stillbirth, blood-borne viral disease such as hepatitis, and withdrawal in the baby after birth.
• Inhalants (such as glues or aerosols) — increased risk of miscarriage, low birth weight, birth defects and SUDI.

Street drugs such as heroin or methamphetamine are often mixed with unknown substances, which can also harm the pregnancy or baby. Prescription drugs bought on the street and not prescribed for you, such as benzodiazepines, can be very problematic if not taken as directed.

Treatment for opioid dependence#

Methadone and buprenorphine (including buprenorphine-naloxone) are prescription medicines sometimes called pharmacotherapies, used to treat heroin and other opioid dependence. They greatly reduce the risks to the pregnancy and baby compared with continued heroin or other opioid use. Their benefits are reduced if you keep using heroin or other drugs.

General recommendations#

Be guided by your doctor. General advice includes:

• Limit caffeine to less than 200 mg a day — roughly one espresso-style coffee, two cups of instant coffee, four cups of medium-strength tea or hot chocolate, or six cups of cola.
• Avoid energy drinks.
• Avoid or cut down smoking.
• Avoid or reduce illegal drugs.

See your doctor, speak to your midwife or seek drug counselling if you need help to quit smoking, alcohol or other drugs.

Do not assume non-prescription medicines are safe just because you can buy them without a prescription — be advised by your doctor or pharmacist. Whenever possible, use non-drug alternatives for minor concerns during pregnancy. For example:

• Eat small, frequent snacks rather than three large meals to avoid heartburn.
• Use salt-water nasal sprays for nasal congestion.
• Avoid foods or smells that trigger nausea.

Key points#

• Stopping substances during pregnancy can be hard because of past life experiences, ongoing health problems and social stress.
• The risk of a birth abnormality for any baby is about 4 per cent, regardless of what happens during pregnancy.
• Under a common risk system, B1 means animal studies show no increased risk.
• B2 means animal studies are limited but show no apparent increased risk.
• B3 means animal studies show an increased risk, but it is unclear whether this applies to humans.

Where to get help#