pregnancy

Question 1

what is teratogenicity?

Answer 1

the ability of a drug to cause foetal abnormalities or congenital malformations

Question 2

what factors influence teratogenic effects?

Answer 2

dose, route, timing, genetics, environmental factors, and other drugs

Question 3

name 5 known teratogens

Answer 3

thalidomide, isotretinoin, valproate, ACEi, NSAIDs

Question 4

what are the critical phases of human development regarding teratogenic risk?

Answer 4

pre-embryonic (0–17 days): all-or-nothing (survival or miscarriage)

embryonic (day 18–55): greatest vulnerability! organ development

foetal (8 weeks–term): functional defects (e.g. hearing loss)

Question 5

what is the most critical phase for teratogenic risk?

Answer 5

embryonic phase (day 18–55) – organ development occurs

Question 6

what happens if harmful drugs are taken during the pre-embryonic phase?

Answer 6

all-or-nothing effect – either full recovery or miscarriage

Question 7

why should most medications be avoided in the first trimester?

Answer 7

because it’s the highest risk period for structural abnormalities

Question 8

what factors affect a drug’s ability to cross the placenta?

Answer 8

molecular weight, ionisation, lipid solubility, protein binding

Question 9

which drugs cross the placenta easily?

Answer 9

lipid-soluble, non-ionised, low-MW drugs like labetalol (for HTN)

Question 10

which large-molecule drugs do not usually cross the placenta?

Answer 10

insulin and heparin

Question 11

what is the most common mechanism for medicine-related harm in pregnancy?

Answer 11

molecules crossing the placenta into foetal circulation (passive diffusion)

Question 12

what absorption changes occur during pregnancy?

Answer 12

intestine: prolonged gastric emptying time; ↓ gastric acid, ↑ pH → affects drug ionisation and absorption
= ionisation and absorption of weak acids impacted
lungs: ↑ cardiac output and tidal volume = ↑ alveolar uptake of inhaled meds (dose reduction needed)

Question 13

how does pregnancy affect drug distribution?

Answer 13

↑ plasma volume and fat stores → ↓ drug concentration

Question 14

how does plasma volume affect drug levels?

Answer 14

plasma volume ↑ → ↑ Vd → ↓ peak serum concentration
(drugs with a large Vd less affected)
also ↑ Vd of drugs distributed in adipose tissue

Question 15

why are some free drug levels higher in pregnancy?

Answer 15

↓ albumin levels → ↓ protein binding due to dilutional
hypoalbuminaemia in late pregnancy; steroid
and placental hormones occupy protein-
binding sites

Question 16

what happens to hepatic metabolism in pregnancy?

Answer 16

↑ hepatic blood flow alters drug metabolism (faster elimination) (↑progesterone = ↑metabolism of some drugs, ↑oestrogen = ↓ clearance)
↑ stroke vol and HR
→ ↑ cardiac output

Question 17

how is renal elimination affected in pregnancy?

Answer 17

↑ GFR and renal flow → faster clearance of some drugs that are excreted unchanged (takes longer to get to steady state concs of drugs)
↑ activity of renal tubular P-gp = ↓ conc of drugs transported by renal system

Question 18

can medications taken by fathers affect pregnancy?

Answer 18

yes - reproductive toxicity from cytotoxics, radiation, or smoking can impact sperm

Question 19

how long should men wait before conceiving after taking cytotoxics?

Answer 19

typically 6–9 months (2–3 spermatogenic cycles depending on the drug)

Question 20

why is shared decision-making important?

Answer 20

ensures informed consent and builds trust, especially where data is limited

Question 21

what’s the first step in medicine decision-making in pregnancy?

Answer 21

determine if the medicine is essential and if there are non-drug options

Question 22

why is specialist advice crucial for some drugs like valproate?

Answer 22

due to high teratogenic risk; must meet Pregnancy Prevention Programme conditions (high risk of neurodevelopmental disorders)
effective contraception needed
even for 3 months after valproate
stopped

Question 23

what are key benefits for breastfeeding?

Answer 23

mother: improved mental health - oxytocin release, reduced risk of breast and ovarian cancer, reduced risk of osteoporosis, CVD, and obesity
infant: reduced allergies, improved immunological status, nutritionally complete for first 6 months, reduces risks of SIDS, obesity, CVD in adulthood

Question 24

what are some issues with breastfeeding?

Answer 24

mother: pressure - mental health burden, breastfeeding in public - uncomfortable, painful, returning to work is tricky, extra calories needed
infant: premature babies
- deficient in phosphate
- deficient in calories
mothers of very
premature neonates
may cease lactating
before feeding
becomes established

Question 25

how do drugs enter breast milk?

Answer 25

through lipid phase, aqueous phase, and by binding to milk proteins

Question 26

what is the composition of breast milk?

Answer 26

lactose, electrolytes, protein

Question 27

why can large molecules pass through breast milk after the first few days of birth?

Answer 27

there are wide intracellular intracellular gaps in the milk ducts to facilitate passage of immunoglobulins —> to pass on immunity (functional) but also risk of meds into breast milk as large molecules can pass

Question 28

what pharmacokinetic issues affect drug transfer during lactation?

Answer 28

oral bioavailability: if low then baby will not absorb via milk (insulin, LMWH) plasma protein binding: if highly protein bound, less passed via milk (warfarin, ibuprofen) milk : plasma ratio: lower value, smaller amount in milk (iodine - actively transported into milk) fat solubility: lipophilic drugs preferentially dissolve in fat globules of milk - more likely to pass (benzos, amitriptyline) MW: large MW, less likely to pass (heparin; alcohol has LOW MW) absorption from infant gut: may enter into milk but not absorbed by infant's gut (gentamicin, dopamine) 1st pass metabolism: meds undergoing extensive 1st pass less likely to be absorbed by baby (i.e., morphine) neonatal clearance: neonatal kidney/liver function not fully developed → risk of accumulation (i.e., fluoxetine has long half life)

Question 29

what are further considerations?

Answer 29

toxicity of the drug - cytotoxics even in small doses are harmful vs some meds in high doses such as iron are not likely to be harmful relevant infant dose

Question 30

what is the Relative Infant Dose (RID) and what does it mean?

Answer 30

dose received via breast milk <10% = compatible 10–25% = use with caution 25% = contraindicated

Question 31

what is the Relative Infant Dose (RID) threshold considered safe?

Answer 31

<10% is considered compatible with breastfeeding

Question 32

which drugs should be avoided in breastfeeding due to toxicity?

Answer 32

cytotoxics, cocaine, and high RID medications

Question 33

why is drug clearance reduced in breastfeeding neonates?

Answer 33

neonates have immature liver and kidney function

Question 34

how does fat solubility affect drug transfer into milk?

Answer 34

lipophilic drugs (e.g. benzodiazepines, amitriptyline) dissolve in milk fat

Question 35

what factors should be included in information gathering?

Answer 35

gestational age, feeding type, PMHx, DHx, birth method, baby’s age

Question 36

what are reliable resources for pregnancy/lactation medication info?

Answer 36

UKTIS, BNF, LactMed, PMHx/DHx, and specialist consultation

Question 37

what alternatives should be considered before prescribing in pregnancy?

Answer 37

non-pharmacological options, alternative drugs, dose timing

Question 38

when can medicines be timed safely during breastfeeding?

Answer 38

short-acting drugs may be taken after a feed or between feeds

Question 39

why should drugs with long half-lives be avoided in breastfeeding?

Answer 39

they can accumulate and increase risk of neonatal side effects

Question 40

how can breastfeeding be managed around a short medication course?

Answer 40

temporarily interrupt feeding if safe - but avoid if possible

Question 41

what precautions should be taken if a potentially harmful drug must be used?

Answer 41

monitor the infant, use the lowest dose, avoid similar-acting drugs, and choose safer formulations

Question 42

which SSRIs are considered safe in breastfeeding?

Answer 42

sertraline and citalopram

Question 43

why should codeine be avoided in breastfeeding?

Answer 43

risk of ultra-rapid metabolism causing toxicity in the infant (increased s/e such as sedation)

Question 44

is lithium safe in breastfeeding?

Answer 44

no - it’s contraindicated due to high RID and infant risk

Question 45

can Abx be used during breastfeeding?

Answer 45

yes - especially those licensed in children, though temporary lactose intolerance may occur

Question 46

what is the risk of stopping breastfeeding too soon due to meds?

Answer 46

loss of bonding, nutritional benefits, and maternal oxytocin release - may worsen mental health