Secondary hypertension in pregnancy

Most forms of hypertension have no known underlying cause and are known as “essential hypertension” or “primary hypertension.” However, in approximately 10% of the cases, there is a known cause, and thus the hypertension is referred to as secondary hypertension. Blood pressure falls in the first and second trimesters of pregnancy. Therefore, women with high blood pressure before the 20th week of pregnancy are assumed to have preexisting hypertension which may be essential or secondary hypertension. As many women of reproductive age only present for the first time when pregnant, chronic hypertension is often revealed in the first half of pregnancy. In women presenting with hypertension in the first half of pregnancy it is important to look for an underlying cause. Many of these disorders can be cured, leading to partial or complete normalization of the blood pressure. However, it is not cost-effective to perform a complete evaluation of every hypertensive patient, therefore it is important to assess the patient for signs and symptoms that suggest the possibility of secondary hypertension. There are many causes of secondary hypertension and these are summarized inTable 7.1. Many of the disorders listed in this table are common (e.g., renal disease) while others are extremely rare (e.g., pheochromocytoma). Nevertheless, it is important for the obstetrician to be aware of them all and to able to undertake basic steps to exclude them, either on clinical grounds or by more detailed investigation (Table 7.2).