Pregnancy

Pre-existing conditions and non-obstetric disease cause more maternal deaths in the UK than obstetric complications

Pregnant women should receive the same investigations and treatments as non-pregnant patients with avoidance of harm to the foetus wherever possible

Physiological Changes

System	Normal pregnancy	Consider pathology
Cardiovascular	a fall in BP before week 20 (rises back up) Increased HR, SV & CO	persistent BP >140/90 might indicate Pre-eclampsia
Respiratory	Compensated respiratory alkalosis No change in PEFR or VC Altered chemoreceptor sensitivity + $\uparrow$ $O_2$ consumption → $\uparrow$ RR + 10%	Serum bicarb <18 mmol/L Decreased PEFR RR <20/min
Renal	$\uparrow$ renal perfusion, GFR, protein excretion $\downarrow$ urea, creatinine bladder capacity decreases RAAS increased in 1st trimester - smooth muscle dilation increased risk of UTIs	Creatinine >85 $\text{micro}$mol/L (eGRF not valid in pregnancy)
GI	lower oesophageal pressure altered appetite decrease in motility $\uparrow$ water reabsorption constipation, nausea, heartburn
Haematology	Decreased clot lysis (reduced protein S, APC resistance, increased plasminogen activator inhibitors) Increased clot formation (increased factors I, V, VII, VIII, IX, X, XII)

Radiology

If the uterus is positioned outside the imagining field of view, the radiation dose to the foetus is minimal. Exposure from the following is well below the threshold of risk to the foetus:

• Plain radiograph: chest, extremities, spine
• CT: head, chest (but consider radiation to maternal breast in pregnancy

Ultrasound and MRI are generally preferred when imaging abdomen

Drugs

Should always be a balance of risk - drugs different again in lactation

Considered safe	Contraindicated
Penicillins	Tetracycline/Doxycycline
Macrolides	Ciprofloxacin
Low molecular weight heparin	Trimethoprim (1st trimester)
Aspirin	NSADs (3rd trimester)
Labetalol	ACEi
Nifedipine	ARA
Adenosine	Mycophenolate
Prednisolone	Warfarin
Treatment for asthma: Salbutamol, ipratropium, aminophylline, leukotriene antagonists	Live vaccines (MMR, BCG, varicella)