By Neus Ferrando Gilabert BSc, MSc (embryologist).
Last Update: 05/19/2014

The ideal thing would be that women do not take any medication during pregnancy. However, statistics show that most women take some medicine during the gestation period.

Toxic effects on pregnant women of some medicines are still unclear, since, evidently, no clinical trials are performed on pregnant women. However, effects on babies whose mother was taking any medicine during pregnancy have been evaluated.

In some cases, especially women with a chronic health problem or an acute pathology, it may be difficult, not to say inevitable, to avoid taking any medication. Hence the importance of always asking your health care provider in order to assess the risk/benefit balance of the medicine.

The different sections of this article have been assembled into the following table of contents.

Which medicine is harmful?

Medications taken during pregnancy get straight into the fetus through the placenta, having therefore an effect on it.

Early pregnancy is considered as the most critical stage in the whole process, since medicines have a greater impact on the fetus at this stage. In fact, this is the stage in which a medicine is more likely to harm (birth defects, abnormalities, or deformities) or even kill the fetus.

Which medications are safe?

It could also be the case that it is absolutely harmless. Approximately between day 17 and 57, the fetus is especially vulnerable, since that is the moment when its internal organs are developing. This period is known as organogenesis and it is an essential phase during fetal development. For this reason, taking medications at this stage can even lead to miscarriage.

Thus, taking medicines between weeks 5 and 8 is not advisable. After this period, you should talk to your health care provider before taking any medicine. Alternative ways (e.g. natural remedies, rest, drinking plenty of fluids, etc.) to cope with the symptoms may be an alternative to medicines.

Once you have asked your health care provider, please use any medication when strictly necessary and pay attention to medication directions such as how it should be taken (with food or on an empty stomach, for instance) or if it has possible side effects.

Medications that affect the fetus

Some studies on this subject have classified from safe to totally unsafe the following medications:

  • Those classified as safe according to several studies which have shown that they are harmless for the fetus: folic acid and vitamin B6.
  • Those considered to cause birth defects on the fetus: for example, medications used to treat psoriasis or cystic acne.
  • Those classified as totally unsafe: treatments such as chemotherapy, hormones, thyroid medicines, sedatives and painkillers, antibiotics, oral anticoagulants, etc.

Neither is aspirin recommended.

The most important thing to bear in mind during pregnancy is that you should not take any medicines without medical prescription. You should ask your doctor in order to prevent any potential risk both for you and the baby-to-be.

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Authors and contributors

 Neus Ferrando Gilabert
BSc, MSc
Embryologist
Bachelor's Degree in Biology from the University of Valencia (UV). Postgraduate Course in Biotechnology of Human Assisted Reproduction from the Miguel Hernández University of Elche (UMH). Experience managing Embryology and Andrology Labs at Centro Médico Manzanera (Logroño, Spain). More information
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