Prescribing in Pregnancy Flashcards
What are the general principles of prescribing medications during pregnancy? 5
- Use the lowest effective dose for the shortest time
- avoid unnecessary drugs, especially in the first trimester
- assess risk vs. benefit for both mother and fetus
- choose drugs with established safety data in pregnancy.
Why is the first trimester critical in prescribing medications?
Organogenesis occurs during the first trimester (weeks 3–8), so the risk of teratogenic effects is highest during this time.
What are the FDA pregnancy risk categories? (pre-2015)
A: Controlled studies show no risk
B: No evidence of risk in humans
C: Risk cannot be ruled out
D: Positive evidence of risk, but benefits may outweigh risks
X: Contraindicated in pregnancy
Why was the FDA pregnancy categorization system replaced?
It was considered oversimplified; it didn’t adequately reflect available data.
It was replaced in 2015 by the Pregnancy and Lactation Labeling Rule (PLLR), which provides narrative summaries.
What are the effects of retinoids (e.g., isotretinoin) in pregnancy?
Severe birth defects including craniofacial, cardiac, and CNS anomalies.
What are the risks of ACE inhibitors in pregnancy?
Renal dysgenesis, oligohydramnios, fetal hypotension, and skull ossification defects, especially in the second and third trimesters.
How does warfarin affect the fetus?
Warfarin embryopathy (nasal hypoplasia, stippled epiphyses) and CNS defects.
What is phenytoin associated with in pregnancy?
Fetal hydantoin syndrome—growth deficiency, developmental delay, and craniofacial anomalies.
What congenital effects are linked with valproate?
Neural tube defects (especially spina bifida), cognitive impairment.
What are the risks of tetracyclines in pregnancy?
Discoloration of teeth and inhibition of bone growth in the fetus.
Which antibiotics are generally safe in pregnancy?
Penicillins, cephalosporins, and erythromycin.
Which antihypertensives are safe in pregnancy?
Labetalol, nifedipine, and methyldopa.
Which anticoagulant is preferred in pregnancy?
Low molecular weight heparin (LMWH), as it does not cross the placenta.
What factors affect drug transfer into breast milk?
Molecular size, lipid solubility, protein binding, and maternal plasma concentration.
Which drugs are generally considered safe during breastfeeding?
Most antibiotics (penicillins, cephalosporins), paracetamol, ibuprofen, and asthma medications.
Name a drug contraindicated in breastfeeding.
Chloramphenicol (risk of “grey baby syndrome”).
Why is the first trimester (0–12 weeks) the most sensitive period for teratogenic effects?
Because this is the period of organogenesis, when major organs and systems are forming.
What are drug-related risks in the second and third trimesters?
Functional effects (e.g., renal impairment), growth restriction, CNS effects, and preterm labour risks.
Name a drug that is especially risky in the third trimester.
NSAIDs – they can cause premature closure of the ductus arteriosus and oligohydramnios.
Which antiepileptic drug has the highest risk of teratogenicity?
Valproate – associated with neural tube defects, cognitive delay, and autism spectrum disorders.
What antiepileptic is often preferred in pregnancy?
Lamotrigine – considered to have a lower teratogenic risk, though monitoring is required.
What supplementation should be given with antiepileptics in pregnancy?
High-dose folic acid (5 mg daily) preconception and during the first trimester.
Which antibiotics should be avoided in pregnancy? 3
- Tetracyclines – teeth discoloration, bone growth inhibition
- Aminoglycosides – ototoxicity
- Fluoroquinolones – cartilage damage (in animal studies)
Which antibiotics are generally safe?
Penicillins, cephalosporins, erythromycin, and clindamycin.
