In this section
Hypertension during pregnancy includes a number of conditions and occurs in 6-8% of all pregnancies. These conditions include gestational hypertension, pre eclampsia/eclampsia, and chronic hypertension and are responsible for considerable maternal and perinatal morbidity and mortality.1
Blood pressure taken in the sitting position (with the right arm horizontal) that is persistently recorded as being more than 30 mm Hg systolic and/or more than 15 mm Hg diastolic above pre-pregnancy or early pregnancy values or, in the absence of knowledge of pre-pregnancy or early pregnancy values, >140 mm Hg systolic and/or >90 mm Hg diastolic (diastolic blood pressure is recorded with disappearance of the Korotkoff V sound).2
Urine protein that is >300mg/24 hour collection or a spot urine protein:creatinine ratio >25mg/mmol are the two recognised determinants of proteinuria. Note: Semi quantification by dipstick testing may be unreliable.
Oedema is no longer included in the definition of pre eclampsia as it occurs equally in women with and without this condition.
Classification of hypertension in pregnancy
Development of an elevated blood pressure after 20 weeks of pregnancy or in the first 24 hours postpartum. No other signs or symptoms of pre eclampsia or evidence of hypertensive vascular disease is present. Resolution of blood pressure elevation occurs by 12 weeks postpartum. Some women with gestational hypertension will progress to develop the clinical syndrome of pre eclampsia; the rate of progression is determined by the gestational age at the time of diagnosis of gestational hypertension, the earlier in gestation the diagnosis the greater the risk of progression.3
Mild pre eclampsia
Onset of mild hypertension (an increase of 20 mm Hg systolic and/or more than 10 mm Hg diastolic above pre-pregnancy or early pregnancy values or, in the absence of knowledge of pre-pregnancy or early pregnancy values, 140 systolic and/or 90 diastolic) after the 20th week of gestation with proteinuria (>300mg/24 hour collection or spot urine protein : creatinine ratio > 25mg of protein/mmol creatinine), uncomplicated by neurologic symptoms or criteria for the diagnosis of severe pre eclampsia
Severe pre eclampsia
Severe pre eclampsia is diagnosed when:
The diagnosis should also be considered in women with lesser degrees of hypertension, but who have one or more of the following:
The occurrence of convulsions or coma (not caused by trauma or coincidental neurologic disease such as epilepsy) in a woman whose condition also fulfils the criteria for the diagnosis of pre eclampsia.
Note: Use of the term Pregnancy Induced Hypertension is discouraged because it inadequately defines what is a complex multi-system disease condition.
The only definitive treatment for the hypertensive complications of pregnancy is delivery. For this reason, delivery is indicated in women with hypertensive complications at term (37 or more completed weeks) of any severity and in preterm pregnancies with severe disease. There are however several exceptions to these general rules.
Delivery may be delayed in a term pregnancy to achieve cervical favourability by ripening, if:
Pregnancies < 32-34 weeks with severe disease responsive to anti-hypertensive and anti-seizure therapy may be observed with maternal and fetal surveillance, in a high level multi-disciplinary unit setting, to achieve greater fetal maturity.
Rest at home can be used in women with mild gestational hypertension as long as:
Any evidence of maternal and or fetal compromise or failure to respond to outpatient treatment requires hospitalisation.
Special management issues for patients with hypertensive crises (BP of >170/110).
Transfer to a tertiary setting is indicated for:
Magnesium sulphate therapy should be considered prior to transfer in women with severe pre eclampsia, eclampsia or HELLP syndrome.
Assessment of severity in pre eclampsia
All patients with pre eclampsia must be regarded as being at risk of major maternal and fetal complications, but there are certain indicators of particular concern, when they occur in a woman with definite pre eclamspia:
Pre eclampsia usually pursues a course of deterioration, sometimes slowly and sometimes quickly. It may evolve from mild to moderate to severe over a period of hours or days, and requires frequent reassessment by medical staff.
The HELLP Syndrome is a form of severe pre eclampsia. Maternal mortality is reported to be as high as 1-2% .
The elements of this variety of severe pre eclampsia are:
The presence of any one of
in a woman with pre eclampsia is an indicator of severe disease, even if not suggested on other criteria such as severity of hypertension.
Timing of delivery
Deferral of delivery
Consider in patients between 23 and 32 weeks with severe pre eclampsia:
Treatment of pre eclampsia
Given the earlier statement that "The only definitive treatment for the hypertensive complications of pregnancy is delivery", the decision to deliver a woman because of pre eclampsia is a complex one and should take into account all the above indicators of maternal and fetal status, as well as fetal maturity. At very early gestations, it may be justifiable to delay delivery even where there are maternal abnormalities that would provoke delivery at a later gestation. Close maternal and fetal monitoring are mandatory if such a conservative course is pursued, in a high level multi-disciplinary unit setting.
The final decision about timing and mode of delivery in severe pre eclampsia should be made by an Obstetric Consultant, often after Paediatric, Anaesthetic and/or Medical consultation
Except in the situation of acute fetal compromise, urgent delivery is not helpful in pre eclampsia and the mother should be resuscitated before being subjected to the delivery process.
In severe pre eclampsia, delivery must always be preceded by:
5-10mg Hydralazine, given intravenously as a bolus over 5-10 minutes, then by continuous infusion at 5mg/hr, with adjustment of rate to maintain BP <160/100 every 30 minutes until BP 140/90 to 160/100. Reactive tachycardia with Hydralazine may necessitate use of IV beta blockers. Note: Blood pressure should not be allowed to fall below a level of 140/80.
Prevention of Seizures
Level I evidence indicates that magnesium sulphate is the superior drug to use in the prevention and the treatment of eclamptic seizures.9-12 The Magpie Trial found the risk of eclampsia was halved and the risk of placental abruption and overall maternal deaths were reduced (although not significantly) in women treated with magnesium sulphate compared to a control group. However, subgroup analysis suggests that these benefits are primarily seen in countries with high perinatal mortality rates, where blood pressure control and accurate fluid balance management is difficult.13 In addition, adverse effects were more common in the magnesium group.
In the patient with known renal disease or myasthenia gravis, however, phenytoin sodium is the anti-seizure medication of choice. Phenytoin sodium is administered in a total dose of 15mg/kg at an infusion rate of 40mg/min with continuous cardiac and blood pressure monitoring.
Administration of magnesium sulphate
Magnesium sulphate therapy is recommended for severe pre eclampsia when the following factors are present:
Administer intravenous loading bolus dose of 4g of magnesium sulphate over 20 minutes. Magnesium sulphate should be administered via a controlled infusion device.
Monitor the patient to detect magnesium sulphate toxicity - viz:
The magnesium infusion should be stopped and the serum levels re-evaluated if the urinary output is <30 mL/hour, in the absence of previously detected deep tendon reflexes, decreased respiratory rate (12 breaths/min.) or there is evidence of CNS or cardiac depression.
If recurrent seizures occur a further 2 - 4g of MgSO4 is given over 5 minutes. Dose depends on the woman's weight, 2g if <70kg and 4g if >70kg.
The loading dose is followed by a maintenance infusion of 1 g of MgSO4 / hour for at least 24 hours after the last seizure or after birth of the infant. Use 1g per hour as maintenance therapy.
Management of magnesium toxicity
If magnesium toxicity (ie respiratory depression, absent deep tendon reflexes, or altered state of consciousness) is suspected:
Hypotensive therapy should be commenced if the BP is >150 mmHg systolic or >100 mmHg diastolic in the first four postpartum days. Options for hypotensive therapy include:14
Non-acute Hypotensive Therapy
Evidence suggests that hypotensive drug therapy confers no clear benefit to women with mild pre eclampsia.8,15 Randomised control trials of women with mild pre eclampsia remote from term, which compared hypotensive drug therapy with no medication or a placebo, have been reported. In some of these trials, the frequency of proteinuria, progression to severe disease, and neonatal respiratory distress syndrome were higher in the women not treated.16-19 These observations however have not been confirmed in other trials.20-22
In women with severe pre eclampsia, or those who have received treatment for hypertensive crisis, maintenance control of BP is essential for maternal safety to reduce the risk of cerebral events, and prolongation of pregnancy if it is contemplated for fetal benefit. However, the maternal blood pressure must not be lowered too drastically because of the impact on a placental circulation that has adapted to a higher blood pressure. With a lowered blood pressure there may not be adequate placental perfusion.
Management of HELLP syndrome
If the platelet count is sufficiently low to preclude epidural anaesthesia (consult with Consultant Anaesthetist) or to present a hazard for operative delivery, a platelet transfusion should be administered (consult with Consultant Haematologist or Obstetric Physician). Steroid treatment (see Dexamethasone therapy below) is not useful for the acute management of thrombocytopenia, such as in preparation for surgery.
If there is significant bleeding attributed to pre-eclamptic thrombocytopenia at any time in the puerperium a platelet transfusion be given (consult with Consultant Haematologist or Obstetric Physician).
In the absence of bleeding, platelet transfusion be considered in the first 72 hours only if count falls below 40,000 and there is concern at possible bleeding (eg after caesarean section).
If the count remains below 40,000 after 72 hours from delivery without significant bleeding and without sign of impending recovery, consultation with Consultant Haematologist or Obstetric Physician is indicated. In addition, consideration should be given to steroid therapy in view of the possibility of undiagnosed ITP or SLE, or prolonged pre-eclamptic thrombocytopenia. Usual therapy is prednisolone, 40-60mg daily, but dexamethasone may be used (equivalent dose is 6-8mg per day). Such therapy is expected to lead to a gradual rise in the platelet count beginning after 24-48 hours.
In rare cases where severe thrombocytopenia persists, with evidence of microangiopathic haemolysis, consideration should be given to differential diagnosis in addition to the above, including postpartum thrombotic thrombocytopenic purpura and postpartum antiphospholipid syndrome. These disorders may respond to high dose steroids, or may need treatment by apheresis.
High dose Dexamethasone therapy
Women with severe HELLP syndrome may be treated with a high dose regime of Dexamethasone at a dose of 10mg IV every 12 hours until delivery (consult with Consultant Haematologist or Obstetric Physician). Postpartum 10mg every 12 hours is administered until the maternal platelet count is >100,000uL and the LDH is falling. When these conditions are met, two additional doses of dexamethasone 5mg IV are administered - 12 hours apart.23-24
The administration of Ranitidine 150mg BD with a sip of water should be considered when dexamethasone therapy is used.
Women first diagnosed with HELLP syndrome postpartum (1/3 of the women will be first diagnosed postpartum) may be treated with this regimen postpartum.