Medication Use in Pregnancy

Question 1

What are the pt issues surrounding the use of drugs during pregnancy?

Answer 1

1. Pts tend to overestimate risk
2. 1st source of info imp.
3. 1st dr. visit often weeks into pregnancy
4. Lack of info on safety of meds in pregnancy (pregnant women excluded from clinical trials)
5. Societal beliefs
6. Litigation (overly cautious approach by HCPs)

Question 2

What are the stages of embryonic & fetal growth?

Answer 2

Pre-implantation period:
- time from conception –> implantation (1st 2 weeks)
- ALL OR NOTHING (sign. insult will cause death)
- gen. not the cause of malformations

Embryonic period:
- 2-8 weeks POST conception
- organogenesis (dev. of organs & specialized tissues
- formation of organs occur at diff. times
- GREATEST PERIOD OF VULNERABILITY TO TERATOGENS

Fetal period:
- 9 weeks –> birth
- growth & maturation of organs
- anomalies can still occur
- ALWAYS TRY TO FIND OUT TIMING OF EXPOSURE!

Question 3

What are the drug properties which affect the placental transfer of medications?

Answer 3

Majority of drugs cross via PASSIVE DIFFUSION (high in mother, low in baby)

Drug more likely to cross placenta if it is:
- lipophilic
- un-ionized
- LOW molecular weight
- LOW protein binding

Maternal factors:
- placental blood flow
- placental metabolism

With enough time drug levels will equilibrate b/t both sides

Question 4

What effect do teratogens have on the fetus?

Answer 4

Any agent that can disrupt (or halt) the development of an embryo or fetus
- drugs, radiation, environmental agents, chemicals, infections

4 types:
1. Structural malformations
- cleft palate, neural tube defects, limb defects

2. Functional toxicities
   - neurobehavioural effects, deafness, organ function affected, cancer
3. Miscarriage, stillbirths, neonatal death
4. Alterations to growth
   - growth restriction