4.5 Pregnancy-induced hypertension and pre-eclampsia


Normally, blood pressure (BP) slightly decreases during pregnancy. In a pregnant woman, hypertension is defined as BP ≥ 140/90 mmHg. To confirm hypertension, check BP several times, with the woman seated and at rest.

Chronic hypertension is defined as hypertension predating the pregnancy or appearing before 20 weeks LMP.

Pregnancy-induced hypertension (PIH) is defined as isolated hypertension, without proteinuria, that appears after 20 weeks LMP.

Pre-eclampsia refers to pregnancy-induced hypertension accompanied by proteinuria. Preeclampsia carries a significant risk of foetal growth retardation, foetal distress, foetal death, placental abruption and eclampsia.
High BP is the most visible sign of pre-eclampsia. However, pre-eclampsia is a complex disease affecting multiple organs, including liver and kidneys.

The goal of antihypertensive treatment is to prevent the maternal complications of severe hypertension. Treatment is administered if systolic BP is ≥ 160 mmHg or if diastolic BP is ≥ 110 mmHg. The objective is to lower BP to about 140/90 mmHg. Antihypertensive treatment does not improve the foetal prognosis.

Hypertensive treatment in pregnant women should be carried out with caution. It is essential to preserve placental perfusion and to avoid excessive fall in maternal BP.

4.5.1 Diagnosis of pre-eclampsia

– BP ≥ 140/90 mmHg AND proteinuria (1+ or more on dipstick test).
– Other signs may be present: dark urine, low urine output, and oedemas (legs, hands) that appear suddenly or worsen rapidly.

Note: in women with proteinuria and no hypertension, consider urinary tract infection, contamination of urine with blood or vaginal secretions, genito-urinary schistosomiasis in endemic areas, or renal disease. In these cases, monitor continuously, to ensure early detection of pre-eclampsia.

4.5.2 Diagnosis of severe pre-eclampsia

– Systolic BP ≥ 160 mmHg or diastolic BP ≥ 110 mmHg, persistently elevated in spite of treatment.
– Proteinuria (3+ or more on dipstick test or more than 5 g/day).
– Oliguria (urine output < 400 ml/day or < 30 ml/hour).
– Hyperreflexia (overactive knee-jerk response, twitching and spasms).
– Epigastric pain, nausea, vomiting.
– Facial oedema, pulmonary oedema.
– Intense headaches not relieved by paracetamol.
– Buzzing in the ears, visual disturbances.

When feasible, measure platelets and liver enzymes to assess the severity of the disease. The HELLP syndrome (haemolysis, elevated liver enzymes, low platelets) is a potential lifethreatening complication for both the mother and foetus).

4.5.3 Management of isolated hypertension

– Rest and monitoring: BP, weight; look for oedema and proteinuria.

– Measure the fundal height (risk of foetal growth retardation).

– Normal sodium and caloric intake.

– In the event of proteinuria developing, treat as for pre-eclampsia.

– If systolic BP is ≥ 160 mmHg or diastolic BP is ≥ 110 mmHg, give an antihypertensive treatment:
labetalol PO: 200 mg/day in 2 divided doses then increase if necessary, in 100 to 200 mg increments until an effective dose is reached, usually 400 to 800 mg/day in 2 divided doses. If higher doses are required, give in 3 divided doses. Do not exceed 2.4 g/day.
If the mother is taking labetalol, monitor the newborn for at least 72 hours after birth (risk of hypoglycaemia, bradycardia and respiratory distress).
or
methyldopa PO: 500 to 750 mg/day in 2 or 3 divided doses for 2 days, then increase if necessary, in 250 mg increments every 2 to 3 days, until an effective dose is reached, usually around 1.5 g/day. Do not exceed 3 g/day.

In case of treatment failure, these drugs can be associated. Do not stop treatment abruptly.

Diuretics and angiotensin-converting-enzyme inhibitors (captopril, enalapril, etc.) are contra-indicated.

4.5.4 Management of mild pre-eclampsia

Before 37 weeks LMP

– Rest and monitoring: BP, weight, oedema, proteinuria at least once a week.
– Measure the fundal height (risk of foetal growth retardation).
– Normal sodium and caloric intake.
– Do not stop uterine contractions if they occur; let the woman deliver.
– If systolic BP is ≥ 160 mmHg or diastolic BP is ≥ 110 mmHg: labetalol or methyldopa (Section 4.5.3).

Pre-eclampsia is an evolving condition, always deteriorating. As soon as even a single sign of severe pre-eclampsia appears, transfer to a CEmONC facility.

After 37 weeks LMP

– Same monitoring and antihypertensive treatment.
– If there is true intrauterine growth retardation, induce labour for vaginal delivery, or perform a caesarean section.
– If there is no growth retardation, continue to monitor and induce labour as soon as the cervix is favourable.

4.5.5 Management of severe pre-eclampsia

Care is best organized with a multi-disciplinary team comprising obstetrician, anaesthesiologist and midwife.

Delivery

Delivery is imperative within 24 hours, either vaginally or by caesarean section, depending on the state of the cervix, gestational age and condition of the foetus.

Magnesium sulfate treatment

To reduce the risk of eclampsia, administer magnesium sulfate (MgSO4). One of the following regimens may be used:

MgSO4
5 g ampoule
(500 mg/ml, 10 ml)
IV/IM protocol

Loading dose: 4 g by IV infusion in 100 ml of 0.9% sodium chloride over 15 to 20 minutes.
Then
Maintenance dose: 10 g IM (5 g in each buttock), followed by 5 g IM every 4 hours (change sides with each injection).
Continue this treatment for 24 hours after delivery.

or

MgSO4
5 g ampoule
(500 mg/ml, 10 ml)
IV protocol

Loading dose: 4 g by IV infusion in 100 ml of 0.9% sodium chloride over 15 to 20 minutes.
Then
Maintenance dose: 1 g/hour by continuous infusion. Continue this treatment for 24 hours after delivery.

 
• Verify the dosage written on the MgSO4 ampoules (there are different dosages).
• There is a risk of potentially lethal overdose of MgSO4. Have calcium gluconate, the antidote of MgSO4, immediately available (1 g ampoule).

During administration, monitor:
– Patellar reflex (knee-jerk), BP, pulse and respiratory rate every 15 minutes for the first hour of treatment. If there are no signs of overdose, continue monitoring every hour.
– Urine output every hour (insert Foley catheter).

Manifestations of MgSO4 overdose start with disappearance of the patellar reflex then hypotension, arrhythmia, respiratory depression (< 12 breaths/minute). If the patellar reflex disappears, stop MgSO4 immediately and administer calcium gluconate (1 g IV).

If urine output drops (< 30 ml/hour or 100 ml/4 hours): stop MgSO4 and deliver as quickly as possible.

Antihypertensive treatment

If systolic BP is ≥ 160 mmHg or diastolic BP is ≥ 110 mmHg: labetalol or methyldopa (Section 4.5.3).

If the oral route is impossible, use injectable labetalol or hydralazine. When administering, monitor the mother’s BP and pulse and the foetal heart rate.

The dose is adjusted according to changes in BP. Hypertension is controlled when diastolic BP is between 90 and 100 mmHg and systolic BP between 130 and 150 mmHg.

 Respect dosage and administration rate. Administering too much of the drug, or administering it too quickly, can provoke a sudden, excessive fall in maternal BP, with placental hypoperfusion and foetal death. Diastolic BP should not go below 90 mmHg. In the event of hypotension, use Ringer lactate solution to bring the diastolic BP back up to ≥ 90 mmHg.

One of the following regimens may be used:

labetalol
slow IV
(ampoule of 100 mg in 20 ml,
5 mg/ml)

One dose of 20 mg (4 ml) over at least one minute. Check BP 5 and 10 minutes after injection. If hypertension remains uncontrolled, administer another dose of 20 mg and check BP. Administer additional doses, of 40 mg then 80 mg with 10 minutes between each dose as long as hypertension is not controlled. Do not exceed a cumulative dose of 300 mg.

or

hydralazine
slow IV
(20 mg/1 ml vial)

Dilute 20 mg (1 vial of hydralazine reconstituted in 1 ml of water for injection) in 9 ml of 0.9% sodium chloride to obtain 10 ml of solution containing 2 mg hydralazine/ml.
Administer 5 mg (2.5 ml of the diluted solution) over 2 to 4 minutes. Monitor BP for 20 minutes. If hypertension remains uncontrolled, repeat injection. Continue repeating if necessary, waiting 20 minutes between each injection. Do not exceed a cumulative dose of 20 mg.

or

hydralazine
IV infusion
(20 mg/1 ml vial)

Dilute 100 mg (5 vials of reconstituted hydralazine) in 500 ml of 0.9% sodium chloride or Ringer lactate to obtain a 200 micrograms/ml solution.
The initial dose is 200 to 300 micrograms/minute; the maintenance dose is 50 to 150 micrograms/minute.
Administer by increasing the rate up to 20 drops/minute (maximum 30 drops/minute), monitoring the BP every 5 minutes.
As soon as the hypertension is controlled, gradually reduce the rate (15 drops/minute, then 10, then 5) until stopping infusion. Stopping abruptly can trigger a hypertensive crisis.

Notes:
– If the mother receives labetalol, monitor the newborn for at least 72 hours after birth (risk of hypoglycaemia, bradycardia and respiratory distress).
– If anaesthesia is necessary, avoid ketamine. Whenever possible, use spinal anaesthesia.
– Oxytocin may be used in pre-eclampsia, but requires BP monitoring: drops and elevations in BP have been described in rare cases.
– Ergometrine and methylergometrine are contraindicated.
– Pre-eclampsia can appear up to 48 hours after delivery, and on rare occasions even later.

4.5.6 Secondary prophylaxis for severe pre-eclampsia

Acetylsalicylic acid PO: 75 mg/day starting at 12 weeks LMP and continuing until 36 weeks LMP reduces the risk of recurrence during the next pregnancy. If this prophylactic treatment is feasible, recommend that the woman comes for consultation as soon as she knows she is pregnant. There is no point in starting this treatment after 20 weeks LMP10.

During the next pregnancy, calcium supplementation is recommended11 in women with low calcium intake (see Chapter 1, Section 1.2.5).