A 33-year-old Hispanic woman who recently immigrated to the United States with her newborn daughter is presenting to a free clinic for a wellness checkup for her baby. As part of screening for those immigrating or seeking refuge in the United States, she and her child are both evaluated for tuberculosis. The child’s purified protein derivative (PPD) test and chest radiograph are negative, and although the mother’s chest radiograph is also negative, her PPD is positive. She states that she is currently asymptomatic and has no known history of tuberculosis (TB). The mother’s vital signs include: blood pressure 124/76 mm Hg, heart rate 74/min, and respiratory rate 14/min. She is advised to begin treatment with isoniazid, supplemented with pyridoxine for the next 9 months. She asks about the potential for harm to the child if she begins this course of treatment since she is breastfeeding. Which of the following is the most appropriate response to this patient’s concerns?

“You may breastfeed your baby because you are asymptomatic and because neither isoniazid nor pyridoxine will harm your child.”

“You should not breastfeed your baby for the next 9 months because isoniazid in breast milk can damage your child’s liver.”

“You should not breastfeed your baby for the next 9 months because pyridoxine in breast milk can damage your child’s liver.”

“You should not breastfeed your baby because she is at greater risk for infection with TB than for adverse side effects of your treatment regimen.”

“You may breastfeed your baby because pyridoxine will prevent isoniazid from causing peripheral neuropathy.”

A 3670-g (8 lb 1 oz) male newborn is delivered to a 26-year-old primigravid woman. She received adequate prenatal care and labor was uncomplicated. She has chronic hepatitis B infection and gastroesophageal reflux disease. Her only medication is ranitidine. She admits to smoking cannabis and one half-pack of cigarettes daily. She drinks two beers on the weekend. The mother is apprehensive about taking care of her baby and requests for some information regarding breastfeeding. Which of the following is a contraindication to breastfeeding?

Seropositive for cytomegalovirus

A 32-year-old G2P0A1 woman presents at 36 weeks of gestation for the first time during her pregnancy. The patient has no complaints, currently. However, her past medical history reveals seizure disorder, which is under control with valproic acid and lithium. She has not seen her neurologist during the past 2 years, in the absence of any complaints. She also reports a previous history of elective abortion. The physical examination is insignificant. Her blood pressure is 130/75 mm Hg and pulse is 80/min. The patient is scheduled to undergo regular laboratory tests and abdominal ultrasound. Given her past medical history, which of the following conditions is her fetus most likely going to develop?

Intrauterine growth restriction

A 44-year-old woman with high blood pressure and diabetes presents to the outpatient clinic and informs you that she is trying to get pregnant. Her current medications include lisinopril, metformin, and sitagliptin. Her blood pressure is 136/92 mm Hg and heart rate is 79/min. Her physical examination is unremarkable. What should you do regarding her medication for high blood pressure?

Discontinue lisinopril and initiate labetalol

Discontinue lisinopril and initiate aliskiren

Continue her current regimen and add a beta-blocker for increased control

Discontinue lisinopril and initiate candesartan

A 29-year-old woman presents to a medical office complaining of fatigue, nausea, and vomiting for 1 week. Recently, the smell of certain foods makes her nauseous. Her symptoms are more pronounced in the mornings. The emesis is clear-to-yellow without blood. She has had no recent travel out of the country. The medical history is significant for peptic ulcer, for which she takes pantoprazole. The blood pressure is 100/60 mm Hg, the pulse is 70/min, and the respiratory rate is 12/min. The physical examination reveals pale mucosa and conjunctiva, and bilateral breast tenderness. The LMP was 9 weeks ago. What is the most appropriate next step in the management of this patient?

Beta-HCG levels and a transvaginal ultrasound

Beta-HCG levels and a transabdominal ultrasound

Beta-HCG levels and a pelvic CT

Medication safety in pregnancy for USMLE Step 1: High-Yield OB/GYN Lessons

FDA Risk Categories - Alphabet Soup Shake-up

Old System (Pre-2015): Letter categories (A, B, C, D, X) ranked risk from controlled human studies to clear contraindication.
- A: No risk (human studies).
- B: No evidence of risk (animal studies).
- C: Risk cannot be ruled out.
- D: Positive evidence of risk.
- X: Contraindicated.
New System (PLLR - 2015): Pregnancy and Lactation Labeling Rule.
- Abolished letter categories for a narrative approach.
- Requires detailed subsections: Pregnancy, Lactation, and Females & Males of Reproductive Potential.

FDA Pregnancy and Lactation Labeling Rule Comparison

⭐ The PLLR provides a risk summary but requires clinical judgment, moving away from the perceived (and often misinterpreted) simplicity of the A/B/C/D/X system.

Common Teratogens - The Pregnancy Poison List

Teratogenic Exposure Outcomes by Gestational Stage

General Principle: Avoid all non-essential medications, especially during the first trimester (organogenesis).

Drug/Substance	Category & Effect
Alcohol	Fetal Alcohol Syndrome (FAS): smooth philtrum, thin upper lip, microcephaly, cognitive deficits.
ACE Inhibitors/ARBs	Renal dysgenesis, oligohydramnios, skull ossification defects.
Isotretinoin	Extremely teratogenic. Craniofacial, cardiac, and CNS defects. Requires iPLEDGE program.
Phenytoin	Fetal hydantoin syndrome: craniofacial abnormalities, hypoplastic nails, developmental delay.
Valproate	High risk of neural tube defects (e.g., spina bifida). Dose-dependent effect.
Lithium	Ebstein's anomaly (atrialization of right ventricle).
Warfarin	Bone and cartilage defects (stippled epiphyses), nasal hypoplasia. Use heparin/LMWH instead.
Tetracyclines	Discolored teeth, inhibited bone growth.
Methotrexate	CNS and limb abnormalities.
Thalidomide	Phocomelia (limb reduction defects).

📌 Mnemonic: "Teratomas"

Thalidomide
Epilepsy drugs (Phenytoin, Valproate)
Retinoid (Isotretinoin)
ACE inhibitors/ARBs
Third element (Lithium)
Oral contraceptives (Androgens)
Methotrexate
Alcohol
Smoking/Warfarin

Safe Swaps - Green-Light Alternatives

Condition	Avoid (Teratogenic)	Safe Alternative(s)
Hypertension	ACE Inhibitors, ARBs	Labetalol, Nifedipine, Hydralazine, Methyldopa
Anticoagulation	Warfarin	LMWH (e.g., Enoxaparin), Unfractionated Heparin
Diabetes	Most Oral Agents	Insulin, Metformin, Glyburide
Epilepsy	Valproate, Phenytoin	Levetiracetam, Lamotrigine (requires ↑ folate)
Pain/Headache	NSAIDs (esp. 3rd tri)	Acetaminophen (Paracetamol)
Depression	Paroxetine	Sertraline (Zoloft), Citalopram

High‑Yield Points - ⚡ Biggest Takeaways

ACE inhibitors & ARBs are contraindicated, causing fetal renal damage and oligohydramnios.

Avoid warfarin (causes nasal hypoplasia); use heparin/LMWH for anticoagulation.

Valproate and carbamazepine are strongly associated with neural tube defects.

Isotretinoin is a potent teratogen requiring two forms of contraception.

Avoid NSAIDs in the 3rd trimester to prevent premature ductus arteriosus closure.

Treat maternal hypertension with labetalol, nifedipine, or methyldopa.

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