There are several medications that cannot be given to pregnant women because they can cross the placental barrier and disturb the development of the embryo or fetus. These medications are termed teratogenic medications. Teratogens can cause the pregnancy to fail or lead to a developmental abnormality that will be present at birth (birth defect).
Animal experiments generally indicate that the neuroleptic antipsychotic haloperidol, is not teratogenic. However, it has been shown to be embryotoxic at high doses in animal models. Currently, no controlled studies to check the effects in humans have yet been performed.
Some unconfirmed studies of pregnant women have suggested that haloperidol can damage the fetus. However, the women were exposed to several drugs during their pregnancy meaning causal relationships could not be established in these studies.
Studies have also reported that newborns exposed to antipsychotic drugs are at risk of withdrawal symptoms and extrapyramidal symptoms (relating to motor nerves that control involuntary reflexes and movement). The research suggests that after delivery, these babies may exhibit signs of agitation, tremor and hypotonia, for example.
Due to the uncertainty that surrounds the safety of this drug for use in pregnancy, the generally accepted principle is that haloperidol should only be administered during pregnancy if the benefit clearly outweighs the potential risk to the fetus.
Significant amounts of haloperidol have been found in the breast milk of lactating mothers who have been prescribed the drug. Breastfed infants have also been found to display extrapyramidal symptoms. Breastfeeding is therefore not generally recommended for mothers who are taking haloperidol.