Epidemiology of hypertension in pregnancy
Hypertension in pregnancy is the most common health disorder found in pregnant women, present in approximately 10% of this population. Nearly 8 – 13% of pregnant women in the United States are affected by this condition, and the prevalence is increasing in developing countries. Hypertension in pregnancy represents a major problem as it is one of the 3 main causes of death in pregnant women. About 50% of pregnant women with this condition develop hypertension in late pregnancy, especially last month.
Hypertensive disorders during pregnancy are divided into 4 categories including chronic hypertension, preeclampsia-eclampsia, preeclampsia superimposed on chronic hypertension, and gestational hypertension.
Chronic hypertension is a blood pressure of 140 / 90 mm Hg or above for both systolic or diastolic, or one of those values separately, present before pregnancy or manifested before the 20th week of pregnancy. It is lasting more than 12 weeks after giving birth.
Preeclampsia and eclampsia
Preeclapmsia is a syndrome that occurs in pregnancy which is besides hypertension, characterized by increased concentration of proteins in urine (proteinuria). These disorders may affect the development and growth of the fetus. Some signs and symptoms of preeclampsia include swelling (edemas) which may cause upper abdominal pain if they occur in the liver; severe headaches, and visual disturbances.
Eclampsia represents the complication of preeclampsia, where a pregnant woman with preeclampsia develops epileptic-like seizures, caused by cerebral edemas.
Preeclampsia superimposed on chronic hypertension
This condition occurs in pregnant women who were previously diagnosed with hypertension and it’s characterized by worsening of hypertension after the 20th week of pregnancy accompanied by proteinuria.
Gestational hypertension is a type of hypertension that occurs in pregnant women after the 20th week of pregnancy in women who didn’t have hypertension before. This condition often draws back after 12 weeks after the delivery. Gestational hypertension isn’t accompanied by proteinuria.
Treatment of hypertension in pregnancy
Treatment of hypertension in pregnancy includes non-pharmacological measures and antihypertensive drugs. Women who are previously diagnosed with mild to medium hypertension usually continue to receive their therapy, if the drug isn’t contraindicated in pregnancy in which case it should be replaced with another one.
Non-pharmacological measures are recommended to all women with hypertension. Women need to check their general condition and blood pressure regularly, resting frequently. It is advised to sleep in a left lateral position (left side). It is not advised to restrict the intake of calories and sodium, as sodium intake restriction can decrease the volume of intravascular fluid, and diet restriction may affect fetal growth, which isn’t desirable.
Treatment of hypertension in pregnancy with drugs are needed in women with blood pressure ≥ 140 / 90 mm Hg and with gestational hypertension, preeclampsia superimposed on chronic hypertension or with subclinical organ damage. In other conditions, treatment with drugs is recommended if blood pressure is ≥ 150 / 95 mm Hg.
Drugs which are mostly used in these conditions are methyldopa, labetalol, and niphedipine.
Methyldopa is proven to be effective and safe in pregnancy by numerous clinical trials. It works on the central nervous system, as it is metabolically changed into α-methylnorepinephrine which activate α2 receptors decreasing blood pressure.
Lebetalol is both alpha and beta blocker. It decreases the blood pressure by inhibiting the β1 receptors in the heart, and α1 receptors within the vascular smooth muscle. It is effective in hypertension in pregnancy.
Niphedipine is a calcium channel blocker. It blocks the L-type calcium channels in arteries causing vasodilation, decreasing the blood pressure.