Hypertension in Pregnancy

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Chapter: Essential pharmacology : Antihypertensive Drugs

A sustained BP reading above 140/90 mm Hg during pregnancy has implications both for the mother and the foetus: reduction of BP clearly reduces risks. Two types of situations are possible:


HYPERTENSION IN PREGNANCY

 

A sustained BP reading above 140/90 mm Hg during pregnancy has implications both for the mother and the foetus: reduction of BP clearly reduces risks. Two types of situations are possible:

 

·      A woman with preexisting essential hypertension becomes pregnant.

·      Pregnancy induced hypertension; as in toxaemia of pregnancy—preeclampsia.

 

Toxaemic hypertension is associated with a hyperadrenergic state, decrease in plasma volume (despite edema) and increase in vascular resistance.

 

In the first category the same therapy instituted before pregnancy may be continued. However, one of the ‘safer’ drugs listed below may be substituted if one of the ‘drugs to be avoided’ was being used.

 

 

Antihypertensives To Be Avoided During Pregnancy

 

Diuretics: Tend to reduce blood volume— accentuate uteroplacental perfusion deficit (of toxaemia)—increase risk of foetal wastage, placental infarcts, miscarriage, stillbirth.

 

ACE inhibitors, AT1 antagonists: Risk of foetal damage, growth retardation.

 

Nonselective β blockers: Propranolol has been implicated to cause low birth weight, decreased placental size, neonatal bradycardia and hypoglycaemia.

 

Sod. nitroprusside: Contraindicated in eclampsia.



Antihypertensives Found Safer During Pregnancy

 

Hydralazine

Methyldopa (a positive Coombs’ test occurs, but has no adverse implication).

Dihydropyridine CCBs: discontinue before labour as they weaken uterine contractions.

Cardioselective β blockers and those with ISA, e.g. atenolol, metoprolol, pindolol, acebutolol: may be used if no other choice.

Prazosin and clonidine—provided that postural hypotension can be avoided.

 

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