Studies on the use of metoclopramide in pregnancy suggest that the medication appears to be safe for use throughout a pregnancy, although more controlled data may be necessary to confirm this. The U.S. Food and Drug Administration (FDA) classifies it as a category B medication, indicating that no adverse effects have been observed in animals. Medical researchers believe it does not increase the risk of birth defects on the basis of retroactive review of patient medical records, looking at pregnancies and outcomes for women who have taken metoclopramide in pregnancy.
Determining the safety of medications in pregnancy is extremely challenging, as there are serious ethical issues to consider. Consenting adults can freely participate in clinical trials and trials can be stopped as soon as it becomes apparent that severe adverse effects are appearing. Fetuses cannot sign up for participation in clinical trials, and damage to a fetus may not become apparent until after labor and delivery. Thus, much data is based on a combination of animal trials and use in limited populations of women who choose to accept the risk of a medication because the benefits appear to outweigh the chances of a problem.
Metoclopramide works by attaching to dopamine receptors in the central nervous system. It inhibits vomiting and increases the rate of gastric emptying. A doctor may prescribe metoclopramide in pregnancy to treat severe vomiting, which is most commonly a problem in the first trimester. The first trimester is also a period of critical concern with fetal development, as much of the framework for the nervous system is laid during this stage of pregnancy. Medications that act on the central nervous system are a potential cause for concern, especially when they readily pass over the placenta as metoclopramide does.
Review of patient outcomes shows that there is not an increased risk of birth defects and other complications associated with the use of metoclopramide during pregnancy, during any trimester. These studies also show that neurological development for children born to mothers who take this medication appears to proceed normally. This suggests that using metoclopramide in pregnancy does not damage the developing nervous system.
There are, however, concerns about the use of this medication while breastfeeding. The drug is secreted in breast milk and could potentially cause complications for a developing baby. It can also cause symptoms like uncontrolled tremors in patients who take the drug, which may be a concern for pregnant women considering metoclopramide in pregnancy to control nausea.
