Hypertensive disorders complicating pregnancy are common and forms one of the deadly triad along with hemorrhage and infection. This results in much of the maternal morbidity and mortality related to pregnancy. It is not yet known why pregnancy incites or aggravates hypertension.
CLASSIFICATION
According to the classification proposed by the National High Blood Pressure Education Program (2000) there are five types of hypertensive diseases complicating pregnancy.
1) Gestational hypertension also known as pregnancy-induced hypertension (PIH)
2) Preeclampsia
3) Eclampsia
4) Preeclampsia superimposed on chronic hypertension
5) Chronic hypertension
Hypertension has been defined as a blood pressure of 140/90 mm Hg or greater or an increase of 30 mm Hg systolic or 15 mm Hg diastolic over the baseline value on atleast two occasions.
GESTATIONAL HYPERTENSION (PIH) Gestational Hypertension is defined as hypertension that develops for the first time in pregnancy after 20 Sweeks of gestation. It is not accompanied by proteinuria and blood pressure returns to normal within 12 weeks postpartum. Final diagnosis can only be made postpartum.
PREECLAMPSIA Preeclampsia is characterised by a rise in blood pressure accompanied by proteinuria, and edema may be present. Proteinuria is described as 300 ntg or more of urinary protein per 24 hours or persistent 30 mg/dl (1+ dipstick) in random urine samples. Preeclampsia may be mild or severe. A diagnosis of severe preeclampsia is made when the diastolic blood pressure is 110 mm Hg or more, persisternt proteinuria 2+ or more, presence of symptoms such as headache, visual disturbance and upper abdominal pain. There may be elevation of liver enzymes, raised serum creatinine and thrombocytopenia.
ECLAMPSIA Eclampsia is the occurrence of seizures in ures in a woman with preeclampsia. The seizures are grand mal and may appear before, during or after labour. Postpartum eclampsia occurs frequently within the first 24 hours after delivery. Rarely, it may occur 48-72 hours after delivery.
INCIDENCE AND RISK FACTORS
The incidence varies from 8 to 10%.
RISK FACTORS
Parity: Gestational hypertension occurs more commonly in nulliparous women
Race and ethnicity: There is a familial tendency to the development of both eclampsia and preeclampsia suggesting a genetic predisposition.
Complications of pregnancy: Preeclampsia is more common in multiple pregnancy, hydramnios, yesicular mole etc.
Diseases complicating pregnancy: The risk of development of preeclampsia is increased in maternal diabetes, hypertension and renal disorders.
Other factors: Emotional stress and environmental factors may contribute as a risk factor.
PREECLAMPSIA
Pathogenesis of Preeclampsia/Eclampsia
Normal pregnancy is characterised by a marked increase in plasma volume, glomerular filtration rate and renal blood flow. There is considerable increase in total body sodium and also an expansion of the extracellular fluid space in which the extra sodium is located. In contrast, preeclampsia is characterised by a reduced volume, reduced glomerular filtration rate and renal blood flow. There is sodium retention and shift of sodium into the arterial walls which may be a factor in the increased sensitivity to pressor agents in preeclampsia
Vasospasm is basic to pathophysiology of preeclampsia and eclampsia. Vascular constriction causes resistance to blood flow and accounts for the development of arterial hypertension. It is likely that vasospasm also exerts a damaging effect on vessels. Angiotensin II causes endothelial cells to contract and these vascular changes with local hypoxia of the surrounding tissues lead to hemorrhage, necrosis and other end organ disturbances observed in severe preeclampsia. There are certain endocrine changes that occur in preeclampsia. Plasma levels of renin, angiotensin II and aldosterone are increased during normal pregnancy, whereas in hypertensive disorders there is a decrease in these values towards the normal non-pregnant range. A potent mineralocorticoid, deoxycorticosterone is significantly increased in the plasma during the third trimester of pregnancy.
Electrolyte concentrations do not differ appreciably in women with preeclampsia compared with those of normal pregnancy unless there has been vigorous diuretic therapy, sodium restriction, or administration of water with sufficient oxytocin to produce diuresis.
Prostaglandins are considered to mediate vascular reactivity during pregnancy. There is evidence that prostacyclin production is decreased significantly and thromboxane A2 significantly increased in preeclampsia as compared to normal pregnancy PGE2 is a vasodilator which is decreased preeclampsia.
In recent years, the other factors that are considered to play a role are nitric oxide, endothelins and vascular endothelial growth factor.
ECLAMPSIA
This is a convulsive disease occuring in pregnant, parturient or puerperal women, usually characterised by high blood pressure, albuminuria, edema with symptoms such as headache, dizziness, disturbances of vision, epigastric pain, convulsions and sometimes coma. Depending on whether the convulsions occur before, during, or after labour, eclampsia is designated as antepartum, intrapartum or postpartum.
Eclampsia is a preventable disease. Efficient antenatal care has almost eliminated this disease in countries where such care is available and is utilised by the pregnant mothers. It is more common in primigravidas than among multigravidas. It has been suggested that eclampsia occurs more frequently when the humidity is greater, and particularly during winter and rainy season.
Etiology and pathology: These are the same as described in preeclampsia.
Clinical features: In a large number of cases of eclampsia, the signs and symptoms of preeclampsia are present. In cases of fulminant variety, no signs or symptoms may be present and a fit may be the first warning. As soon as a diagnosis of imminent eclampsia is made and the treatment started, then eclampsia may be averted.
The Eclamptic Convulsion or Fit
When the woman actually develops the convulsive attack, four stages are recognised:
1) Premonitory stage: The convulsive movements usually begin about the mouth in the form of facial twitchings. This may last from a few seconds to half a minute. few seconds to 1/2 a Hinube
2) The tonic stage: The entire body becomes rigid in a generalised muscular contraction, the features are distorted, the arms flexed and the hands clenched, the body being in a condition of tonic spasm. This may persist for 15 to 204 seconds, 15-205
3) The clonic stage: In this stage, there is alternate contraction and relaxation of the muscles. Suddenly, the jaws begin to open and close violently followed by eyelids. The other facial muscles and then all muscles alternately contrac and relax in rapid succession. The tongue may be bitten by the violent action of the jaws. This phase may kast about a minute. Throughout the seizure the diaphragm has been fixed, with respiration halted, and the face may be cyanosed. There is froth in the mouth; the breathing becomes stertorous. If not properly protected, the patient may fall from the bed and injure herself.
4) Coma: In this stage, the convulsive movements cease, and a few jerks or twitchings may occur at intervals. The patient lies quiet, breathes stertorously; coma supervenes and the respirations gradually quieten down. The duration of coma after a convulsion is variable. In favourable cases, the patient wakes after a short time and is not consciousy of anything that has taken place earlier. In very severe cases, the coma persists from one convulsion to another and death may result before she awakens.
CHRONIC HYPERTENSION
A woman suffering from hypertension may become pregnant. Such a pregnancy may be uneventful or may give rise to complications. Hypertension predisposes to preeclampsia. In the majority of cases when the blood pressure continues to rise in spite of anti-hypertensive therapy, proteins may appear in the urine indicating superimposition of preeclampsia. However, it is not uncommon to see cases with very high blood pressure with no proteinuria.
Differential Diagnosis
It must be remembered that hypertension may be diagnosed for the first time in early pregnancy when she reports for a routine check-up. There may be many causes of underlying hypertension and appropriate clinical examination and investigations may need to be done. Various conditions considered in differential diagnosis include essential familial hypertension, arterial abnormalities such as Renovascular hypertension, co-arctation of aorta renal diseases such as 5 glomerulonephritis, polycystic kidney and connective tissue disorders.
MANAGEMENT
Management essentially consists of anti-hypertensive therapy as described earlier and careful monitoring of pregnancy for early detection of intrauterine growth restriction or development of preeclampsia.
Chronic Hypertension with Superimposed Preeclampsia When a patient with chronic hypertension develops preeclampsia then the investigations and management are the same as described for preeclampsia.
PROGNOSIS IN HYPERTENSIVE DISORDERS COMPLICATING PREGNANCY
The prognosis may be considered from two points of view - immediate and remote.
Immediate prognosis: The response in mild cases if diagnosed early and treated efficiently, is usually good, and hence the prognosis for the mother and baby is favourable. If, however, the diasease is severe and the case neglected, then the patient may have convulsions (eclampsia) and the prognosis is not good for both mother and fetus. Sometimes premature separation of placenta may occur adding to the dangers to mother and child.
Remote prognosis: There is evidence to say that about 40% of the patients who develop hypertension during pregnancy develop vascular hypertension in later life. Recurrent preeclampsia in subsequent pregnancy is also known.
HELLP SYNDROME
The discussion on preeclampsia will not be complete without considering this important complication. In HELLP Syndrome, there is Hemolysis, Elevated Liver enzymes and Low platelets. Liver involvement in preeclampsia-eclampsia is serious and is freqrently accompanied by evidence of other organ development, especially the kidney.