Why is chlortalidone best avoided for treating hypertension or oedema during pregnancy?

Chlortalidone is best avoided for hypertension or oedema during pregnancy because diuretic use may be associated with hypovolaemia, increased blood viscosity and reduced placental perfusion, with reports of foetal bone marrow depression, thrombocytopenia, and foetal and neonatal jaundice associated with thiazide diuretics.