Hypertension or high blood pressure is a common health risk affecting both men and women. It usually presents a life-long challenge for affected individuals to keep their blood pressure at optimum levels and confines many to taking antihypertensive drugs on daily basis. Blood pressure levels can become high during pregnancy which may be the first time it is observed in the pregnant woman or may have had it even before she became pregnant. Irrespective of the case, high blood pressure in pregnancy is something that should be controlled and managed properly to ensure a very successful pregnancy.
Raised blood pressure is common in pregnancy and potentially dangerous, associated with both maternal and fetal mortality. Blood pressure readings > 140/90mmHg are generally considered abnormal in both the pregnant and non pregnant woman. The normal resting blood pressure is near above 120/80mmHg. In pregnancy, plasma volume increases which leads to vasodilation to allow blood pressure remain low. If this vasodilation is counteracted by arteriolar spasm, hypertension can result which creates a reduction in the perfusion of all organs including the uterus and placental site. Every pregnancy requires a routine checking of the blood pressure and this can be done whether at home or more preferably at the clinic for accuracy.
CLASSIFICATION OF HYPERTENSION IN PREGNANCY
There are 3 classifications of hypertension in pregnancy on the basis of when high blood pressure levels were first discovered in the woman.
- Chronic hypertension : high blood pressure existing before pregnancy and persists after delivery.
- Pregnancy Induced Hypertension (PIH) : high blood pressure are absent before pregnancy and first noticed the current pregnancy after 20 weeks gestation and disappears after delivery. PIH can present with just high blood pressure, in which case it is referred to as gestational hypertension. When proteins are seen in the urine (proteinuria), it is called pre-eclampsia and when proteinuria is present with seizures, it is termed eclampsia.
- Chronic hypertension with pre-eclampsia or eclampsia : a woman with hypertension before getting pregnant can progress to have pre-eclampsia or eclampsia before 20 weeks gestation.
PREGNANCY INDUCED HYPERTENSION (PIH)
Gestational hypertension is defined as when blood pressure is > 140/90mmHg in a current pregnancy. It can be associated with additional clinical features as in the case of pre-eclampsia and eclampsia.
Pre-eclampsia is specifically associated with pregnancy and occurs mainly in women with their first pregnancy usually in the second trimester. It is characterised by blood pressure > 140/90 mmHg with proteinuria in a previously normotensive woman. Proteinuria is an indication of renal failure which will mean an impaired placental function and consequent threat to the fetus. It is important to rule out other non-hypertensive causes of proteinuria which include
- Contamination of urine
- Urinary tract infection
- Renal diseases
- Connective tissue disorder
- Othostatic proteinuria
Causes of pre-eclampsia
Pre-eclampsia is a multisystemic disorder and in severe cases can affect liver function and the clotting system. Although the actual cause is unclear, the trophoblast has been associated to the cause of pre-eclampsia. Other risk factors associated with pre-eclampsia include
- Primigravida (first pregnancy)
- Advanced age
- Preexisting hypertension
- Family history of PIH or hypertension
- Multiple pregnancy
- Gestational diabetes
- Hydatidiform mole
- Severe rhesus sensitization
Diagnosis of pre-eclampsia
Pre-eclampsia can be asymptomatic but common complaints are of swollen feet (pedal edema). Blood pressure readings are > 140/90mmHg and proteinuria present. Severe pre-eclampsia however can present with marked clinical features like
- Frontal headaches
- Visual disturbance
- Epigastric pain
- Increased tendon reflexes
Laboratory investigations recommended for diagnosing and managing pre-eclampsia involves
- Full blood count
- Serum uric acid
- BUE and creatinine
- Urinalysis and culture
- Liver function test
- Random blood sugar
- Blood clotting profile
- Ultrasound scan for fetal monitoring
Management of pre-eclampsia
Treatment objective is to prevent complications such as stroke and eclampsia, and to deliver the fetus in severe pre-eclampsia (imminent eclampsia). Management processes involve
- Admission to the hospital if high blood pressure is present with proteinuria and evidence of fetal compromise.
- Blood pressure monitoring every 15 minutes or 30 minutes until it is reduced or stabilised.
- Antihypertensives like hydralazine, labetalol or nifedipine can be used to taper down blood pressure levels with care.
- Delivery of the fetus is the ultimate treatment and the timing and route of the delivery is dependent on the fetal and maternal well-being.
Eclampsia is a complication of pre-eclampsia and characterised by a rapid rise in blood pressure of > 160/110mmHg and associated with proteinuria and convulsions or fits which is similar to that of epilepsy. Fits are repetitive and have short duration of 60 to 90 seconds.
The causes and risk factors of eclampsia are similar to that of pre-eclampsia. Additional clinical features include convulsions, unconsciousness, bleeding tendency and coma.
Management of eclampsia
Eclampsia is an obstetric emergency to be treated with immediate effect. The management objectives are to protect the patient from injury during seizures, prevent further fits, to lower blood pressure, prevent maternal mortality and deliver the baby when stable. Management protocols involve
- Admission to the hospital
- Prevent patient from falling or biting tongue during fits, maintain the airway and ensure patient is laid on her side to prevent aspiration pneumonitis.
- Resuscitate patient with intravenous fluids with caution and prevent further fits with magnesium sulphate or diazepam.
- Taper down blood pressure with adequate antihypertensives very cautiously.
- Deliver the baby once there is no fits.
COMPLICATIONS OF PREGNANCY INDUCED HYPERTENSION (PIH)
- Intrauterine growth retardation
- Fetal hypoxia and intrauterine death
- Placenta abruption
- HELLP syndrome
- Cardiac failure
- Preterm delivery
K. P. Hanretty : “Hypertension in pregnancy ” Obstetrics illustrated (6th edition)