Prescribing in Pregnancy

Question 1

Which drugs cross the placenta

Answer 1

Most drugs cross Placenta to certain extent; Potentially Teratogenic or Foetotoxic; Large Molecular drugs e.g. Heparin, Insulin do not cross
o Increasing maternal age also leads to increasing risk of need for medications

Question 2

Manifestations of drug crossing the placenta

Answer 2

Manifestations include Dysgenesis of Foetal Organs, IUGR or Intrauterine death

Question 3

Pre embryonic exposure

Answer 3

Conception to 17 days after; Adverse Effects usually result in Miscarriage

Question 4

Embryonic exposure

Answer 4

Day 17 – 55; Congenital Malformations more likely due to Rapidly diving tissues;
The early the insult, the greater the damage

Question 5

Foetal exposure

Answer 5

From 8 weeks to term; Effects tend to impact Foetal Growth and Organ function

Question 6

Principles of prescribing in pregnancy 1

Answer 6

Benefits of prescribing ongoing medications in pregnancy and breastfeeding often outweighs potential risks; Pre-pregnancy Assessment for WCBA to switch to alternative medications

Question 7

Principles of prescribing in pregnancy 2

Answer 7

Avoid first trimester medications where possible; Use drugs which have previous experience
of use in pregnancy; Start low and titrate if necessary
• Information can be available from Organisation of Teratology Information Specialists (OTIS)

Question 8

Common Teratogenic Drugs: BP Meds

Answer 8

ACE Inhibitors, ARBs (Renal Malformations, Oligohydramnios)

Question 9

Common Teratogenic Drugs:AED

Answer 9

Phenytoin (Foetal Hydantoin Syndrome), Valporate, Carbamazepine,
Lithium (Ebstein’s Anomaly)

Question 10

Common Teratogenic Drugs: Antibiotics

Answer 10

Trimethoprim in the first trimester, Nitrofurantoin in lead-up to delivery,
Aminoglycosides (Congenital Deafness and Ototoxicity), Chloramphenicol (Grey Baby)

Question 11

Common Teratogenic Drugs: Hormonal

Answer 11

Androgens (Masculinisation and Virilisation)

Question 12

Common Teratogenic Drugs: Warfarin

Answer 12

Avoided in first trimester, and lead-up to delivery

Question 13

Common Teratogenic Drugs: Antithyroid meds

Answer 13

Can lead to Foetal Goitre and Hypothyroidism

Question 14

Common Teratogenic Drugs: Alcohol

Answer 14

Foetal Alcohol Syndrome; Nicotine does not lead to malformations but common;
cause of IUGR (due to Uterine artery restriction); Caffeine can lead to Low Birthweight, Health
problems in later life, and in high enough doses Miscarriage

Question 15

Common Teratogenic Drugs: Others

Answer 15

Retinoic Acid (Craniofacial Malformations, Cleft Palate, Thymic Aplasia, NTDs),
Methotrexate (Antineoplastic agents), Ibuprofen should be avoided after 30 weeks (risk of closure of PDA and Oligohydramnios)