Prescribing in Pregnancy

Question 1

How common is medication use during pregnancy?

Answer 1

> 90% of women take drugs during pregnancy = painkillers (12%), antibiotics (11%), antacids (8%), folic acid and iron

Question 2

What are some common self-medicated drugs taken during pregnancy?

Answer 2

NSAIDs, St John’s wart, herbal preparations

Question 3

What drugs won’t cross the placenta?

Answer 3

Drugs with large molecular weight

Question 4

What actions encompass pharmacokinetics?

Answer 4

Absorption, distribution, metabolism and elimination

Question 5

How may pregnancy affect absorption of drugs?

Answer 5

Morning sickness may affect absorption

Question 6

How can pregnancy affect pharmacokinetics?

Answer 6

Decreased protein binding = increased free drug
Increased liver metabolism of some drugs
Elimination of renally excreted drugs increases

Question 7

How does pregnancy increase volume of distribution?

Answer 7

Increases plasma volume and fat stores

Question 8

Does pregnancy alter pharmacodynamics?

Answer 8

No = no significant change

Question 9

How is prescribing managed pre-pregnancy?

Answer 9

Folic acid = 400mcg daily for 3 months before conception and for 1st three months of pregnancy
Counselling for chronic conditions
Optimise therapy to choose safest drug

Question 10

What does the first trimester carry risk of?

Answer 10

Risk of early miscarriage and period of greatest teratogenic risk = avoid drugs if possible

Question 11

When is the period of greatest teratogenic risk?

Answer 11

4th - 11th weeks gestation

Question 12

What are some common drugs that are teratogenic?

Answer 12

ACE inhibitors = renal hypoplasia
Androgens = virilisation of female foetus
Anti-epileptics = cardiac/facial/limb/neural tube defects
Cytotoxics = multiple defects, abortion
Lithium = CV defects Methotrexate = skeletal defects
Warfarin = limb and facial defects

Question 13

What normally occurs in the second and third trimesters?

Answer 13

Growth of foetus and functional development

Question 14

What effects can drugs have on the foetus in the second and third trimesters?

Answer 14

Intellectual impairment and behavioural abnormalities

Toxic effects on foetal tissue

Question 15

How can drugs have an adverse effect on labour?

Answer 15

Progress of labour, respiratory depression, bleeding

Adaption of foetal circulation = premature closure of ductus arteriosus

Question 16

What adverse effects can drugs have on the baby after delivery?

Answer 16

Withdrawal syndrome or sedation

Question 17

What were the negative effects of diethlystilbestrol?

Answer 17

Urological malignancies in boys

Vaginal adenocarcinomas in girls aged 15-20

Question 18

What does untreated epilepsy carry a risk of?

Answer 18

Untreated epilepsy has higher incidence of congenital malformations than in women with treated epilepsy

Question 19

How may pregnancy impact epilepsy?

Answer 19

May increase seizures (10%) = changes in plasma concentration of drugs (persistent vomiting, increased clearance)

Question 20

What are frequent seizures during pregnancy associated with?

Answer 20

Lower verbal IQ, hypoxia, bradycardia, antenatal death and maternal death

Question 21

What do anti-epileptic drugs increase the risk of?

Answer 21

Congenital malformations = 20-30% risk if on 4 drugs, monotherapy is preferred as lower risk

Question 22

What anti-epileptics should be stopped during pregnancy?

Answer 22

Valproate and phenytoin

Question 23

How much folic acid should be prescribed to women with epilepsy during pregnancy?

Answer 23

5mg daily

Question 24

Is insulin safe to take during pregnancy?

Answer 24

Yes = may need to change dose

Question 25

What does poor diabetic control during pregnancy increase the risk of?

Answer 25

Congenital malformations and intra-uterine death

Question 26

What diabetic medication must be stopped during pregnancy?

Answer 26

Sulfonylureas = switch to insulin

Question 27

What happens to blood pressure during the second trimester?

Answer 27

It falls

Question 28

What drugs should be used to treat hypertension during pregnancy?

Answer 28

Labetalol, methyldopa or nifedipine MR

Question 29

What anti-hypertensives should be avoided during pregnancy?

Answer 29

Avoid ACE inhibitors and ARBs | Beta blockers may inhibit foetal growth in late pregnancy

Question 30

What are some common acute problems that occur during pregnancy and their preferred treatment?

Answer 30

Nausea and vomiting = cyclizine safest Pain = paracetamol Heartburn = antacids UTI = nitrofurantoin, cefalexin, trimethoprim if 3rd trimester

Question 31

What is the leading cause of maternal death during pregnancy?

Answer 31

VTE = pregnancy increases risk of VTE by 10%

Question 32

What are all women encouraged to do during pregnancy to reduce risk of VTE?

Answer 32

Mobilise and stay adequately hydrated

Question 33

What should women at high risk of VTE be prescribed?

Answer 33

Thromboprophylaxis with LMWH = give at delivery and up to 7 days post partum

Question 34

What are the risk factors for VTE?

Answer 34

Obesity, age >35, smoking, parity >3, previous DVT, C-section = considered high risk of 2 or more risk factors

Question 35

How should DVT or PE during pregnancy be treated?

Answer 35

Using therapeutic dose of LMWH

Question 36

Why should warfarin be avoided during pregnancy?

Answer 36

Teratogenic in early pregnancy | Carries risk of haemorrhage during delivery

Question 37

Do drugs tend to enter breastmilk?

Answer 37

Yes = most drugs enter breastmilk, especially small molecules and lipophilic drugs

Question 38

What can affect the amount of drug a baby receives through breastmilk?

Answer 38

Feeding pattern = longer feeds have higher amounts of fat soluble drugs in milk

Question 39

Why may drugs accumulate in a baby?

Answer 39

They have immature metabolisms

Question 40

What is an example of a drug that is actively concentrated in breastmilk?

Answer 40

Phenobarbitone = causes suckling difficulties

Question 41

What are some drugs that can cause problems when they are transferred via breastmilk?

Answer 41

``` Amiodarone = neonatal hypothyroidism Cytotoxics = bone marrow suppression Benzodiazepines = drowsiness Bromocriptine = supresses lactation ```

Question 42

What are some effects of drugs on babies?

Answer 42

``` Tetracycline = staining of bones and teeth Phenytoin = cleft lip and palate Valproate = neural tube defects (spina bifida, anencephaly) ```

Question 43

What are the facial features caused by foetal alcohol syndrome?

Answer 43

Short palpebral fissures, flat midface, short nose, indistinct philtrum, thin upper lip, epicanthal folds, low nasal bridge