Merck Manual

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Some Drugs That Can Cause Problems During Pregnancy *

Some Drugs That Can Cause Problems During Pregnancy *

Examples

Possible Problems

Antianxiety drugs

Benzodiazepines (such as diazepam, alprazolam, or lorazepam)

When the drug is taken late in pregnancy, very slow breathing or a withdrawal syndrome (causing irritability, shaking, and exaggerated reflexes) in the newborn

Antibiotics

Aminoglycosides (such as amikacin, gentamicin, neomycin, streptomycin, and tobramycin)

Damage to the fetus's ear (ototoxicity), resulting in deafness

In women or fetuses with G6PD deficiency, the breakdown of red blood cells

Possibly gray baby syndrome (a serious and often fatal disorder)

Fluoroquinolones (such as ciprofloxacin, ofloxacin, levofloxacin, and norfloxacin)

Possibility of bone and joint abnormalities (seen only in animals)

In women or fetuses with G6PD deficiency, the breakdown of red blood cells

In women or fetuses with G6PD deficiency, the breakdown of red blood cells

Sulfonamides (such as sulfasalazine and trimethoprim- sulfamethoxazole)

When the drugs are given late in pregnancy, jaundice and, without treatment, brain damage (kernicterus) in the newborn

With sulfasalazine, much less risk of problems

In women or fetuses with G6PD deficiency, the breakdown of red blood cells

Slowed bone growth, permanent yellowing of the teeth, and increased risk of cavities in the child

Occasionally, liver failure in the pregnant woman

Defects of the brain and spinal cord (neural tube defects), such as spina bifida

Factor Xa inhibitors such as rivaroxaban, apixaban, or edoxaban

Possible risk of bleeding in the pregnant woman or fetus

Heparin

Thrombocytopenia (a decrease in the number of platelets, which help blood clot) in the pregnant woman, possibly resulting in excessive bleeding

Warfarin

Birth defects, intellectual disability, cataracts, and other problems with the eyes in the fetus

Bleeding problems in the fetus and the pregnant woman

Antidepressants

Bupropion

Harmful effects seen in animals, but conflicting evidence for risk of birth defects in newborns

Citalopram

When citalopram is taken during the 1st trimester, increased risk of birth defects (particularly heart defects)

When citalopram is taken during the 3rd trimester, discontinuation syndrome (which includes dizziness, anxiety, irritability, fatigue, nausea, chills, and muscle aches) and persistent pulmonary hypertension of the newborn (the arteries to the lungs remain narrowed after delivery, limiting blood flow to the lungs and thus the amount of oxygen in the bloodstream)

Escitalopram

When escitalopram is taken during the 3rd trimester, discontinuation syndrome and persistent pulmonary hypertension of the newborn

Fluoxetine

When fluoxetine is taken during the 3rd trimester, discontinuation syndrome and persistent pulmonary hypertension of the newborn

Paroxetine

When paroxetine is taken during the 1st trimester, increased risk of birth defects, particularly heart defects

When the drug is taken during the 3rd trimester, discontinuation syndrome and persistent pulmonary hypertension of the newborn

Sertraline

When sertraline is taken during the 3rd trimester, discontinuation syndrome and persistent pulmonary hypertension of the newborn

Venlafaxine

When venlafaxine is taken during the 3rd trimester, discontinuation syndrome

Antiemetic drugs (used to relieve nausea)

Doxylamine and pyridoxine (vitamin B6)

No increased risk of birth defects

Meclizine

Birth defects seen only in animals

Ondansetron

No evidence of birth defects in animals

When ondansetron is taken during the 1st trimester, possible risk of congenital heart disease

Promethazine

No evidence of birth defects in animals

Possible risk of bleeding in the newborn

Antifungal drugs

Amphotericin B

No increased risk of birth defects, but no well-designed studies done in pregnant women

Fluconazole

No increased risk of birth defects after a single low dose

When high doses are taken for most or all of the 1st trimester, increased risk of birth defects, such as abnormalities in the heart, face, skull, ribs, and limbs

Miconazole

No increased risk of birth defects when applied to the skin

Terconazole

No increased risk of birth defects

Antihypertensive drugs

Aldosterone antagonists (drugs that block the action of the hormone aldosterone), such as spironolactone and eplerenone

With spironolactone, possible development of feminine characteristics in male fetuses

With eplerenone, no increased risk of birth defects in animals, but no well-designed studies done in pregnant women

When the drugs are taken late in pregnancy, kidney damage in the fetus, a reduction in the amount of fluid around the developing fetus (amniotic fluid), and defects of the face, limbs, and lungs

When some beta-blockers are taken during pregnancy, a slowed heart rate, a low blood sugar level, and possibly inadequate growth of the fetus (growth restriction) and preterm birth

Low blood pressure in the mother

When calcium channel blockers are taken during the 1st trimester, birth defects of the fingers and/or toes

When the drugs are taken later in pregnancy, inadequate growth of the fetus

A decrease in the levels of oxygen, sodium, and potassium and in the number of platelets in the fetus's blood

Inadequate growth of the fetus

Antipsychotic drugs

Haloperidol

Harmful effects in animals

When haloperidol is taken during the 1st trimester, possibly birth defects in the limbs

When haloperidol is taken during the 3rd trimester, increased risk of the following:

  • Repetitive, involuntary movements (extrapyramidal symptoms)

  • Restlessness, irritability, shaking, difficulty breathing, and feeding problems (symptoms of drug withdrawal) in the newborn because at birth, passage of the drug from the mother through the placenta stops

Lurasidone

No evidence of harmful effects in animals

When lurasidone is taken during the 3rd trimester, increased risk of the following:

  • Repetitive, involuntary movements

  • Restlessness, irritability, shaking, difficulty breathing, and feeding problems (symptoms of drug withdrawal) in the newborn because at birth, passage of the drug from the mother through the placenta stops

Olanzapine

When olanzapine is taken during the 3rd trimester, increased risk of the following:

  • Restlessness, irritability, shaking, difficulty breathing, and feeding problems (symptoms of drug withdrawal) in the newborn because at birth, passage of the drug from the mother through the placenta stops

Risperidone

No evidence of increased risk of birth defects, but no well-designed studies done in pregnant women

When risperidone is taken during the 3rd trimester, increased risk of the following:

  • Repetitive, involuntary movements

  • Restlessness, irritability, shaking, difficulty breathing, and feeding problems (symptoms of drug withdrawal) in the newborn because at birth, passage of the drug from the mother through the placenta stops

Carbamazepine

Some risk of birth defects, including neural tube defects (such as spina bifida)

Bleeding problems in the newborn (hemorrhagic disease of the newborn), which can be prevented if pregnant women take vitamin K by mouth every day for a month before delivery or if the newborn is given an injection of vitamin K soon after birth

Lamotrigine

No increased risk of birth defects

Levetiracetam

Minor bone abnormalities seen in animals

No studies done in pregnant women

Phenobarbital

Same as those for carbamazepine

Phenytoin

Increased risk of birth defects (such as cleft lip and heart defects)

Bleeding problems in the newborn

Trimethadione

High risk of birth defects (such as cleft palate and defects of the heart, skull, face, hands, and abdomen)

Risk of a miscarriage

Valproate

Some risk of birth defects, including cleft palate, neural tube defects (such as a meningomyelocele), and defects of the heart, face, skull, spine, and limbs

Chemotherapy drugs

Actinomycin

Possibility of birth defects (seen only in animals)

Busulfan

Birth defects such as underdevelopment of the lower jaw, cleft palate, abnormal development of the skull bones, spinal defects, ear defects, and clubfoot

Inadequate growth of the fetus (growth restriction)

Chlorambucil

Same as those for busulfan

Colchicine

Possibility of birth defects (seen in animals)

Abnormalities in sperm in sons

Cyclophosphamide

Same as those for busulfan

Doxorubicin

Heart problems, depending on the dose taken

Birth defects

Mercaptopurine

Same as those for busulfan

Methotrexate

Same as those for busulfan

Vinblastine

Possibility of birth defects (seen only in animals)

Vincristine

Possibility of birth defects (seen only in animals)

Mood-stabilizing drug

When lithium is taken during the 1st trimester, increased risk of birth defects (mainly of the heart)

When lithium is taken later in pregnancy, lethargy, reduced muscle tone, poor feeding, underactivity of the thyroid gland, and nephrogenic diabetes insipidus in the newborn

Aspirin and other salicylates

Ibuprofen

Naproxen

When the drugs are taken in large doses, possibly miscarriages during the 1st trimester, a delay in the start of labor, premature closing of the connection between the aorta and artery to the lungs (ductus arteriosus), jaundice, necrotizing enterocolitis (damage to the lining of the intestine), and (occasionally) brain damage in the fetus (kernicterus) and bleeding problems in the woman during and after delivery and/or in the newborn

When the drugs are taken late in pregnancy, a reduction in the amount of fluid around the developing fetus

When low doses of aspirin are taken, no significant risk of birth defects

Opioids

Buprenorphine

No evidence of increased risk of birth defects but may have other harmful effects on the fetus or newborn

Restlessness, irritability, shaking, difficulty breathing, and feeding problems (symptoms of drug withdrawal) in the newborn because at birth, passage of the drug from the mother through the placenta stops

Codeine

Hydrocodone

Hydromorphone

Meperidine

Morphine

Restlessness, irritability, shaking, difficulty breathing, and feeding problems (symptoms of drug withdrawal) in the newborn

If high doses are given in the hour before delivery, possibly drowsiness and a slowed heart rate in the newborn

Methadone

Restlessness, irritability, shaking, difficulty breathing, and feeding problems (symptoms of drug withdrawal) in the newborn

Chlorpropamide

Glyburide

Metformin

Tolbutamide

A very low blood sugar level in the newborn

Insulin usually preferred

Sex hormones

Danazol

When this drug is taken very early in pregnancy, masculinization of a female fetus’s genitals, sometimes requiring surgery for correction

Synthetic progestins (but not the low doses used in oral contraceptives)

Same as those for danazol

Skin treatment

Isotretinoin

Birth defects, such as heart defects, small ears, and hydrocephalus (sometimes called water on the brain)

Intellectual disability

Risk of miscarriage

Thyroid drugs

Methimazole

An enlarged or underactive thyroid gland in the fetus

Scalp defects in the newborn

Propylthiouracil

An enlarged or underactive thyroid gland in the fetus

Liver damage in the mother

Radioactive iodine

Destruction of the thyroid gland in the fetus

When the drug is given near the end of the 1st trimester, a very overactive and enlarged thyroid gland in the fetus

Increased risk of childhood cancer

Triiodothyronine

An overactive and enlarged thyroid gland in the fetus

Vaccines

Potential infection of the placenta and developing fetus

Potential but unknown risks

Other drugs

Corticosteroids

Possibly a cleft lip when these drugs are taken during the 1st trimester

Hydroxychloroquine

No increased risks at the doses usually used

Isoniazid

Possible harmful effects on the liver or damage to the peripheral nerves (causing abnormal sensations and/or weakness)

Loratadine

Possibly in sons, a birth defect of the urethra in which the opening of the urethra is in the wrong place (hypospadias)

Pseudoephedrine (a decongestant)

Narrowing of the blood vessels in the placenta, possibly reducing the amount of oxygen and nutrients the fetus receives and thus resulting in inadequate growth before birth

Possible risk of a defect in the wall of the abdomen that allows the intestines to protrude outside the body (called gastroschisis)

Vitamin K

In women or fetuses with G6PD deficiency, destruction of red blood cells (hemolysis)

*Unless medically necessary, drugs should not be used during pregnancy. However, drugs can be essential to maintain the health of the pregnant woman and the fetus. In such cases, a woman should talk with her health care practitioner about the risks and benefits of the prescription drugs she is taking before she stops taking them. She should not stop taking them on her own.

Opioids are used to relieve pain. However, they also cause an exaggerated sense of well-being, and if used too much, they can cause dependence and addiction.

G6PD = glucose-6-phosphate dehydrogenase.