The mother's physical condition is essential for the successful delivery of the baby. Certain medical conditions can be a hindrance in the path of normal pregnancy. High blood pressure is a condition that increases the mortality or morbidity rate during pregnancy. The prevalence of hypertension during pregnancy is around 28 %. Thirty-six percent of cases of pregnancy mortality in the United States are related to hypertension-related disorders. Therefore, understanding the pathophysiology behind such conditions is essential.
What Is High Blood Pressure?
The pressure exerted by the blood against the arterial wall is known as blood pressure. During the blood flow, pressure is generated by the force of the heart pumping, known as systolic pressure. Another is the pressure generated between two heartbeats, known as diastolic pressure. In a normal scenario, the normal range of systolic blood pressure is 120-139 mm Hg and diastolic blood pressure is 90 mm Hg. When the pressure crosses this normal limit, it is known as high blood pressure or hypertension.
Based on the type, high blood pressure in pregnancy can be divided into four types. These are:
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Chronic hypertension in pregnancy.
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Gestational hypertension.
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Preeclampsia-eclampsia.
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Preeclampsia superimposed on chronic hypertension.
How to Measure Blood Pressure?
During pregnancy, blood pressure is measured in different ways. The most common method to measure blood pressure is the traditional method with the help of a sphygmomanometer. But in many cases, it has shown inaccurate results or cannot show minor variations. Two other extensively used methods are:
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Ambulatory Blood Pressure Monitoring (ABPM): In this method, the blood pressure is monitored for 24 hours while you move around, engaging in daily activities of life.
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Hyperbaric Index (HBI): This index is calculated from the date of ABPM. In this method, the correlation between the data and kidney function is evaluated.
What Is Chronic Hypertension in Pregnancy?
This type of blood pressure is detected before the 20th week of pregnancy and does not resolve untill 12 weeks after delivery. 5 % of the cases of hypertension during pregnancy belong to this category. On the basis of severity, this incidence of high blood pressure can be categorized into two types. These are:
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Mild Hypertension: In this condition, the systolic blood pressure is 140 to 159 millimeters of Hg, and the diastolic blood pressure is between 90 to 109 millimeters of Hg.
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Severe Hypertension: In this case, the systolic blood pressure is more than 160 millimeters of Hg, and the diastolic pressure is more than 110 millimeters of Hg.
Based on etiology, this can also be divided into:
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Primary Hypertension: This type of hypertension is not related to any disorder or pathology.
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Chronic Hypertension: This type of hypertension is related to various systemic disorders. Systemic conditions associated with these conditions are:
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Renal Disorders: Renal conditions like renal artery stenosis (decreased diameter of the renal artery) and nephritis (inflammation of the nephron) cause this.
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Collagen Vascular Disorders: Disorders like systemic lupus erythematosus (a type of auto-immune disorder) and scleroderma (an auto-immune disorder of connective tissue) cause this.
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Endocrinopathy: Conditions like pheochromocytoma (a type of tumor of the adrenal gland), Cushing’s syndrome (a disease caused by excessive cortisol levels), and hyperthyroidism (excessive secretion of thyroid hormone) are involved.
What Is Gestational Hypertension?
This is also known as pregnancy-induced hypertension. Such conditions are diagnosed after 20 weeks of pregnancy. Around 17 % of first-time pregnant women suffer from such conditions. The etiology of these conditions is unknown. The systolic pressure is more than 140 millimeters of Hg, and the diastolic pressure is more than 90 millimeters of Hg in these cases. No systemic disorder is associated with gestational hypertension. Renal disorders, such as protein in the urine, are also absent in this case.
What Is Preeclampsia and Eclampsia?
This type of blood pressure also develops after the 20th week of pregnancy and is associated with various organ dysfunctions and protein in the urine. In this type, systolic pressure of more than 160 millimeters of Hg, and diastolic pressure of more than 100 millimeters of Hg are observed. The protein excretion from the urine is greater than 300 milligrams in 24 hours.
The responsible factor associated with this type of hypertension is maternal immunological intolerance of foreign fetal genes. Also, abnormal placentation is highly correlated with the onset of such conditions. Inadequate invasion of fetal cytotrophoblasts (a type of proliferative epithelial cell) caused by these factors is responsible for insufficient remodeling of the spiral arteries, and eventually, reduced perfusion of the placenta. This hypoperfusion causes reduced oxygenation in the placenta and initiates inflammatory pathways. As a result, protein in the urine, reduced platelet count, and defective coagulation in the blood can be seen.
If the onset of clinical features is before the 34th week of pregnancy, it is called early-onset. If the onset is after the 34th week, it is termed as late onset.
The clinical manifestations are:
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Development of convulsion due to reduced blood supply in the brain. This is called eclampsia and may not be associated with other symptoms of eclampsia.
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Reduced urine output.
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Swelling of various parts of the body.
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Difficulty in breathing and accumulation of fluid in the lungs.
What Is Preeclampsia Superimposed on Chronic Hypertension?
This is the most dangerous condition associated with the maximum cases of maternal death in pregnancy. In this condition, symptoms of preeclampsia are observed in patients suffering from chronic hypertension. About 20 % of women suffering from chronic hypertension show the development of features of preeclampsia. These patients show symptoms like:
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Protein in the urine.
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Liver dysfunction.
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Renal insufficiency.
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Decreased platelet count.
What Are the Risk Factors?
The risk factors associated with hypertension in pregnancy are:
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Pre-existing systemic diseases.
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Familial history of hypertension and pregnancy hyperfiction.
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Smoking and chronic alcoholism.
What Are the Complications?
Hypertension is responsible for decreased oxygen supply to the fetus. As a result, the growth of the fetus is restricted. This may also lead to the separation of the placenta from the uterine wall. Injury to other organs, like the liver, is also observed in pregnancy hypertension. This may also cause premature delivery of the baby and excessive bleeding during delivery. The development of cardiovascular disorders and maternal and fetal deaths is also evident in such cases.
Conclusion
Hypertension in pregnancy is a serious complication. Several factors, like pre-existing systemic disorders, smoking, and obesity, play a vital role in the development of such conditions. Preeclampsia and eclampsia are dire conditions, and doctors should always monitor the symptoms of such conditions. If adequate care and attention is not taken, these conditions can lead to maternal and fetal death.
