obstetrics

Question 1

define teratogenesis - list some teratogens

Answer 1

dysgenesis of fetal organs evidenced either structurally or functionally

can include restricted growth, death, carcinogenesis and malformations

ACEi, methotrexate, sodium valproate, phenytoin, warfarin, thalidomide, tetracycline, anti-thyroid drugs, carbamazepine, lithium

Question 2

placenta’s key role

Answer 2

nutrition

immunity

excretion

endocrine function

Question 3

describe crossing of placenta

Answer 3

99% of drugs will

non-ionised, lipid soluble - diffuse faster than ionised hydrophilic drugs

high MW (heparin, insulin) - tend not to cross

Question 4

respiratory changes during gestation

Answer 4

increased oxygen consumption
increased minute ventilation
increased tidal volume
increased alveolar ventilation
increase in respiratory rate - not as much compared to tidal vol

Question 5

cardiovascular changes during gestation

Answer 5

increased blood vol
increased CO
increased plasma vol and RBC vol

Question 6

predicting PK changes

Answer 6

absorption - CO increases, blood flow to skin increases

distribution - plasma vol increases, total body water increases

metabolism - hepatic metabolism altered

excretion - renal blood flow increases, GFR increases

Question 7

benefits of breast feeding

Answer 7

for baby - less chance of:
diarrhoea and vomiting
infection
constipation
obesity - T2D
eczema

for mother
- reduces risk of breast/ovarian cancer
- strong bond built b/w mother and baby
- burns calories - upto 500 a day
- money saved

Question 8

which types of drugs are safe to prescribe for a breast-feeding mother

Answer 8

highly protein bound drugs

short half-lives

drugs prescribed for neonates

low plasma:milk ratio - lower the ratio - less passes to milk

Question 9

approximate clearance by age

Answer 9

2-3 months premature - 10%

term - 33%

1-2 months - 50%

3-6 months - 66%

> 6 months - 100%

Question 10

what type of drugs favour excretion into milk

Answer 10

low plasma protein binding, low MW, high lipophilicity, cationic drugs

Question 11

drugs with high infant exposure

Answer 11

amiodarone
carbimazole
isoniazid
lithium
metronidazole
theophylline
phenobarbitone
propylthiouracil

Question 12

drugs with reported toxicity in breast-fed infants

Answer 12

alcohol
caffeine
cocaine
lithium
nicotine
doxepin
fluoxetine
phenobarbital
theophylline

Question 13

define milk to plasma ratio

Answer 13

ratio between drug conc. in milk and maternal plasma (MP ratio)

exposure index links MP ratio, milk intake and infant drug clearance

Question 14

exposure index (%) equation

Answer 14

100 x MP ratio x A / infant drug clearance

A - milk intake
Cl - expressed in ml/kg/min

Question 15

what are the physiological changes during pregnancy

Answer 15

absorption - decreased GI motility, decreased gastric acid secretion, increased gastric pH

distribution - increased body weight and body fat, increased extracellular fluid and total body water, decreased albumin conc.

metabolism - hepatic metabolism altered

excretion - increased GFR, increased CrCl

Question 16

importance of vitamin D during pregnancy

Answer 16

reduces risk of pre-eclampsia and gestational diabetes

reduces risk of getting low birth-weight baby

reduces risk of severe bleeding after birth

Question 17

effects of babies born with Vit D deficiency

Answer 17

neonatal tetany (hypocalcaemic seizures)

impaired fetal growth and long bone development

rickets

effects on fetal lung development - childhood wheeze and allergy