Medication Effects on Fetal Development
Some medications can affect fetal development; they are called teratogens. The study of abnormal fetal development caused by teratogens is called teratology.
When a birth defect occurs, we want to know why it happened. This can
be frustrating because in many instances we are unable to determine a
The first 13 weeks of development (the
first trimester) are the most critical time for a fetus exposed to
teratogens. If an embryo is exposed during the first 2 weeks of
development, the pregnancy might end in miscarriage. The most critical
period of fetal development during the first trimester is between weeks
2 and 8.
The FDA is updating labels on prescription medication to include a fetal-risk summary.
This will provide an indication of the possible drug effects on a
developing baby. It is also updating labels to include information on
the amount of a medication that may be present in breast milk. Included
will be information on milk production and ways to reduce exposure for
Although the first trimester is very
important, your baby’s systems continue to grow and to develop
throughout your pregnancy. Exposure to some substances can harm a baby
even after the first trimester.
Talk to Your Healthcare Provider about Medications You Use
The best time to discuss current health
concerns is before you become pregnant, but this isn’t always possible.
If you discover you’re pregnant and are concerned about the medications
you use, talk to your healthcare provider about it as soon as possible.
At your first prenatal visit, discuss all
prescription and over-the-counter medicines, herbs, vitamins and
minerals you take on a regular basis. You may have to stop taking a
particular substance or adjust the dosage.
Never stop taking any medication you use for a chronic health problem without first consulting your healthcare provider! Some medication cannot and should not be stopped during pregnancy.
Medication Safety Guidelines
You’re an important part of your
healthcare team, especially during pregnancy. You have to make many
decisions about how you will take care of your body during this
important time. The suggestions below can help you decide what
substances you can use before and during pregnancy.
•Don’t use any unnecessary drugs while trying to conceive.
•Avoid all medications during the first trimester, if possible. If you must take a medication, consult your healthcare provider.
to your healthcare provider openly and honestly about medications you
use. If you have a problem you normally treat with over-the-counter
drugs, ask how to treat it during pregnancy.
•If you must use a prescription medication, ask your healthcare provider to prescribe it in its least potent strength.
You may be wondering about taking some
medications you may have normally taken before pregnancy. See the chart
on the opposite page that addresses different categories of
Medication Classification for Pregnancy
Medications a pregnant woman might use
have been categorized by the Food and Drug Administration (FDA) to
indicate the risk to the fetus if a mother-to-be takes them. If you
have questions about any medications you take, ask your healthcare
provider which category it fits into.
well-controlled studies in pregnant women have not shown any risk to
the fetus. Few medications have been tested to this level. A prenatal
vitamin is considered a Category-A medication.
Category B—Animal studies
indicate risk to a fetus is probably low, but human studies have not
been done. Examples include some antibiotics, such as cefaclor.
Category C—There have been no
adequate, well-controlled studies in animals or humans, but it is
believed the medication is safe to use during pregnancy. An example is
Category D—Studies using
animals have shown a harmful effect on the fetus, or studies have not
been done in humans or animals. There is evidence of risk to the fetus,
but it is believed benefits outweigh the risks. One example is
Category X—There is
evidence the medication causes birth defects. Risks outweigh any
potential benefits for women. Accutane is a Category X-medication.