Vol. 14 No 2 | Winter 2012
The safety of drugs in pregnancy and breastfeeding
Dr Debra Kennedy
MBBS, FRACP, Certified Clinical Geneticist (HGSA)

This article is 12 years old and may no longer reflect current clinical practice.

A practical approach to how to deal with counselling women regarding some commonly used medications during pregnancy and breastfeeding.

There is a general perception that any medication exposures during pregnancy pose a potential risk to the fetus. Despite this fear about the safety of medications during pregnancy, several studies from around the world (including Australia) showed that over 90 per cent of women use some form of prescribed or non-prescribed medication during pregnancy.1,2

Thus, despite all their concerns, women are exposed, either intentionally or inadvertently, to a large number of substances during pregnancy and somewhat surprisingly there are relatively few drugs that are considered to be major teratogens and are absolutely contraindicated in pregnancy.

The Australian Categorisation of Drugs in Pregnancy (A-X found in MIMS and other prescribing references) should only be used as a guide to prescribing and should not be used to counsel women about the safety or otherwise of medications in pregnancy. It is also important to remember that the categorisations are not applicable to breastfeeding.3

It is important that all couples considering their reproductive options are informed and understand that for any pregnancy there is a background (population) risk of between three and five per cent of having a baby with a major birth defect or other neurodevelopmental problem that may not be apparent at birth. The risk or otherwise of any exposure needs to be related back to this background risk and the couple must be counselled whether or not a specific exposure has increased their risk of having a baby with an abnormal outcome above the background risk. Overall, the risk for any individual birth defect, such as neural tube defect (NTD), is low (around one per 1000 live births). Even if the relative risk of a defect such as NTD is increased tenfold (RR=10) by a medication such as carbamazepine, the absolute risk for this defect following this particular exposure is still only one per cent.

For practical teratology counselling purposes, pregnancy can be divided into three periods:

  1. ‘All-or none’ period (2–4 weeks amenorrhoea). This is the first two weeks after conception; the time from conception to the first missed period. It is generally believed that exposures during this time do not cause malformations as the conceptus is a mass of dividing stem cells with minimal contact with the maternal circulation and which have not yet differentiated into organs.
  2. Embryonic period (4–10 weeks amenorrhoea). The embryonic period or period of organogenesis is the most critical period of development, during which time exposures can cause structural birth defects such as NTDs, cardiac defects and orofacial clefting. Most teratogens exert their teratogenic effects during a relatively small window of time during this period. For example, thalidomide caused limb defects following exposure between 20 and 35 days post conception.
  3. Fetal period (from ten weeks amenorrhoea). During the fetal period, exposures cannot cause malformations (as the organs have already formed), but may cause disruption of normally formed organs by various mechanisms. Usually these effects are owing to the drug’s recognised pharmacological actions, for example, NSAIDs and ACE inhibitors/angiotensin receptor antagonists can impair fetal renal function and thereby decrease fetal urine production and amniotic fluid volume(oligohydramnios) that causes fetal joint contractures and pulmonary hypoplasia.

Counselling regarding exposures during pregnancy

Clinically timing of the exposure is the most important factor. An agent can only cause a problem if exposure occurs during a critical period of embryonic or fetal development. Thus it is vital to establish the timing of the exposure in relation to the pregnancy and the most accurate way is by early dating ultrasound. In many cases, a woman may be reassured about an exposure of concern simply by having an ultrasound that dates the exposure and having occurred either prior to pregnancy or during the all-or-none period. One exception to this is the major teratogen, isotretinoin, as there have been reports of anomalies in babies exposed in the all-or-none period.

Women with chronic conditions – such as asthma, inflammatory bowel disease, depression, rheumatological conditions, thyroid disease and epilepsy – may well require ongoing medication prior to and during pregnancy as well as while breastfeeding. These women often benefit from face-to-face counselling, ideally before conception, to discuss ideal management of their condition so as to optimise mother and baby’s health before during and after pregnancy. In many conditions, the risks of untreated or under-treated conditions will be higher than any potential risks of medication. This pre-conception consultation is also an important opportunity to address other general health issues including diet, smoking, alcohol use, folic acid/multivitamin supplementation, ensuring immunity to rubella and varicella and exploring potential genetic and other risk factors.

When pregnant women seek advice about past or ongoing exposure to drugs, chemicals or other environmental agents there is often a high level of anxiety. Some women may consider terminating the pregnancy because of information received about potential fetal risks. Counselling must be non-directive and information should be given in a way that a woman (and her partner) can understand the implications of the exposure, assess the risks and make a decision based on as much evidence-based data as possible. Information must be individualised for a woman’s particular situation, in other words, the gestational timing of the exposure/dose/route of administration and the underlying medical condition for which she is taking the medication. It is also important to address what the patient already knows – information she may have received from other sources (lay people, the internet and other healthcare providers).

Table 1. Examples of some drugs of choice for common conditions during pregnancy.4

Condition Drugs of choice Other suitable agents Comment
Allergic rhinitis Topical agents: nasal irrigation, saline sprays, sodium cromo-glycate and corticosteroids

Systemic anti-
histamines, pheniramine, dimenhydrinate, loratadine, cetirizine

Topical decongestants
Topical decongestants should be used according to directions.
Cough/cold Paracetamol
Throat lozenges
Pseudoephedrine and phenylephrine as well as other sympathomimetic agents are used in many cough /cold compounds and nasal sprays. Because of concerns about their vasoconstrictve effects, they should be used with caution especially in the first trimester but women should be reassured after inadvertent exposure.
Constipation Dietary fibre, docusate, bisacodyl, psyllium, paraffin Lactulose, cascara, senna Stimulants such as cascara, senna should not be used on a regular basis but occasional use is safe.
Haemorrhoids Laxatives (see above treatment of constipation) Haemorrhoid preparations contain some of the following ingredients Hydrocortisone and prednisolone Lignocaine and cinchocaine (local anaesthetics)
Witch hazel (hamamelis), aluminium acetate
and allantoin: reduce inflammation.
Zinc oxide: protective.
Peru balsam and benzyl benzoate: mild antiseptic and anti-itching action
Many ointments and suppositories which help relieve symptoms of haemorrhoids are available over the counter. Although there have been no studies confirming the effectiveness of topical haemorrhoid preparations, they are widely used and not considered to increase risks to the baby at any stage of pregnancy. These products help relieve the itch or discomfort of haemorrhoids, but do not treat the underlying varicose veins.
Fever Paracetamol aspirin
Some data suggest aspirin and NSAIDs may be associated with increased miscarriage risk in 1st trimester. Aspirin and NSAIDs should be avoided in 3rd trimester because of premature closure of ductus arteriosus.
Nausea and vomiting of pregnancy Ginger, pyridoxine (vitamin B6) and doxylamine metoclopramide, prochlorperazine, ondansetron Doxylamine and vitamin B6 in combination should be used as first-line treatment for NVP.
Heartburn/reflux Antacids, simethicone H2 antagonists omeprazole and other PPIs Recent studies from Europe and North America have shown that omeprazole is not associated with an increased risk of birth defects or other adverse pregnancy outcomes.
Pain Paracetamol, codeine, morphine, pethidine NSAIDs, aspirin Concerns about maternal tolerance and dependence as well as potential neonatal withdrawal following use of opioids in late pregnancy.

Drugs of choice during pregnancy

Usually, there are several medications available to treat common conditions and there are some medications which are felt to be safer than others for use in pregnancy.

When choosing therapy in pregnancy the usual considerations of efficacy and side effects should be considered in addition to specific fetal safety concerns. Just as in the non-pregnant population, the lowest effective dose of any drug should be used and polytherapy should be avoided wherever possible. However, it is pointless to prescribe medication at sub-therapeutic doses in order to minimise fetal risks. In fact, this is the worst possible strategy as the mother is being inadequately treated while her baby is still being exposed to medication.

Conditions that may need medication during pregnancy can be broadly grouped into the following:

  1. common conditions that can affect pregnant women, in other words, pain, fever, cold and flu, hayfever and allergies
  2. conditions related to or exacerbated by pregnancy, such as nausea and vomiting of pregnancy (NVP), heartburn and gastro-oesophageal reflux, constipation, thrush and hypertension; and
  3. chronic conditions where women may require ongoing medication, such as depression, epilepsy, rheumatoid arthritis and inflammatory bowel disease.

With the majority of drugs, a higher dose within the normal dosing range does not increase the teratogenic risk. Some exceptions to this rule include lamotrigine, warfarin and valproic acid (increased risks of teratogenicity with daily doses >200mg, 5mg and >1000mg, respectively).

Drug Comment
Isotretinoin (Roaccutane) Major teratogen causing craniofacial, ear, cardiovascular and limb defects as well as structural CNS anomalies and neuro-developmental problems. Unfortunately inadvertent exposures in early pregnancy continue to occur due to increasing prescribing rates for relatively minor acne.
Valproic acid Fetal valproate syndrome including neural tube defects, cleft palate, cardiac anomalies and minor facial dysmorphism as well as increased risk of neuro-developmental problems. Risks greater with polytherapy and with doses >1000mg/day.
Warfarin Oral anticoagulant. Use between six and 12 weeks gestation associated with warfarin embryopathy characterised by nasal hypoplasia and stippled epiphyses. Increased risks with doses >5mg. Use later in pregnancy may result in fetal CNS haemorrhage.


In trying to minimise fetal risks, drugs that have been widely used for many years are preferable to newer alternatives. Although the latter may have fewer maternal side effects there is generally less human pregnancy safety data available and thus they should only be used if there is no therapeutic alternative.

Older drugs are also more likely to have longer term follow-up data available. The older anti-epileptic drugs, carbamazepine and lamotrigine, have reassuring long-term neurodevelopmental data available and although newer anti-epileptic drugs, such as gabapentin, are being increasingly prescribed for other indications (such as chronic pain) and because they are often better tolerated there are no long-term neuro-developmental follow-up studies available and thus caution should be advised especially when being used for off-label indications.

Women with conditions such as hyperlipidaemia may take medication to prevent long-term sequelae of their condition. In these situations, the need for medication during pregnancy needs to be balanced with possible fetal risks, especially when the reason for treatment is prevention of long-term complications. Therefore lipid-lowering statins are not generally recommended for use during pregnancy and breastfeeding.

Drugs in breastfeeding

The benefits of breastfeeding in terms of infant nutrition, immunity and maternal bonding are well known. Many breastfeeding women will require medication to treat either a chronic medical problem, such as depression, or an acquired problem, such as mastitis. However, there is relatively limited data about the milk concentration of many medications used by breastfeeding mothers. Because of this dearth of information and the theoretical concerns about the effects of these maternal medications on the breastfed infant, many clinicians err on the side of caution and advise their breastfeeding patients either to avoid taking needed medication while breastfeeding or to stop breastfeeding temporarily (but, unfortunately, this may become permanently).

As with pregnancy, most product information regarding breastfeeding is relatively discouraging, as drug companies are reluctant to recommend the off-label use of medication in this patient group. Performing a literature search or looking at pharmacokinetic parameters such as oral absorption or protein binding data is often more helpful than looking at product information. It is also important to remember that many of the drugs with little breastfeeding data are actually given to the paediatric population (at doses far greater than those found in breast milk) and this may also help in counselling women where there is minimal breastfeeding data available. In fact, there are relatively few drugs that are absolutely contraindicated in breastfeeding. These drugs include cytotoxic agents, iodine-containing drugs, such as amiodarone, and recreational drugs, such as cocaine and ecstasy. Radiocontrast agents are also contraindicated, but most have a very short half-life so that breastfeeding need only be stopped for a very short time.

There are useful online resources for clinicians to access information about medication safety in breastfeeding including Lactmed.5

In conclusion

Information regarding exposures in pregnancy and breastfeeding needs to be up-to date and relevant and given to a woman in a non-directive way that empowers her to make rational decisions and optimise her treatment options. It is far better to delay giving information to a pregnant woman to ensure that it is correct rather than give negative or alarmist advice (even including suggesting termination of an otherwise wanted pregnancy) that is then extremely difficult to undo or unsay. Obstetric drug information services such as MotherSafe can provide information and counselling to healthcare professionals and/or consumers.6 It is therefore vital that obstetricians are aware of the resources that are available so that they can inform their patients of the risks or otherwise of their medications and thus help guide them to make rational decisions and optimise their treatment during pregnancy and breastfeeding.


  1. Henry A, Crowther C. Patterns of medication use during and prior to pregnancy: the MAP study. Aust NZ J Obstet Gynecol 2000; 40(2): 165-172.
  2. Lacroix I, Damase-Michel C, Lapeyre-Mestre M, et al. Prescription of drugs during pregnancy in France. Lancet Nov 18 2000 v356 i9243 p1735.
  3. Kennedy D. Classifying drugs in pregnancy Invited editorial Aust Prescriber 2014; 37:38-40.
  4. www.mothersafe.org.au fact sheets.
  5. Lactmed http://toxnet.nlm.nih.gov/cgi-bin/sis/htmlgen?LACT .
  6. www.tga.gov.au/hp/medicines-pregnancy-odis.htm.

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