Hypertension in pregnancy

SBP ≥170 mmHg and/or DBP ≥110 mmHg

Control blood pressure

• admit to hospital
• commence antihypertensive treatment (Table 1) for all women with a systolic blood pressure ≥170 mmHg or a diastolic blood pressure ≥110 mmHg
• do not allow blood pressure to fall below 140/80 mmHg.

Fluid restriction

• nil by mouth
• 80 ml/hr IV crystalloid.

Observations during acute treatment of severe hypertension

• 15 minutely BP 
• 30 minutely - complete set of vital signs, and assessment of response to treatment 
• continuous oxygen saturation monitoring
• continuous fetal monitoring.

Table 1: Acute treatment with antihypertensive medication

• First line drugs include labetolol and methyldopa.
• Second line agents are hydralazine, nifedipine (if available) and prazosin .
• Multiple agents may be required to control hypertension.
• Angiotensin converting enzyme (ACE) inhibitors and angiotensin receptor blockers (ARBs) are contraindicated in pregnancy. Their use in the third trimester has been associated with fetal death and neonatal renal failure. They can be used post-partum and are compatible with breastfeeding.

Table 2: Ongoing treatment with antihypertensive medication

SBP >140 mmHg and/or DBP >90 mmHg

Hypertension after 20 weeks: assessment and management flowchart

Practice points

• Assess for signs and symptoms of pre-eclampsia.
• Initial assessment and management in a day assessment setting may be appropriate.
• Admit to hospital if features of pre-eclampsia are detected.
• Urgent admission is indicated for: 
  • severe hypertension
  • headache
  • epigastric pain
  • oliguria
  • nausea and vomiting 
  • concerns about fetal wellbeing.
• At <20 weeks gestation, see Chronic hypertension for assessment and management.
• Understand your health service’s capability level – see Victorian Maternity and Newborn Capability Framework.
• If transfer is required, seek assistance from PIPER – 1300 137 650.

Initial assessment

Maternal assessment and investigations

• Perform the following investigations in all women with new onset hypertension after 20 weeks gestation:
  • spot urine protein creatinine ratio (PCR)
  • full blood examination (FBE)
  • urea, creatinine, electrolytes
  • liver function tests (LFT)
  • uric acid.
• If features of pre-eclampsia are present, perform: 
  • urinalysis for protein
  • urine microscopy on a carefully collected midstream urine sample.
• If there is thrombocytopenia or a falling haemoglobin, investigate for disseminated intravascular coagulation (DIC) and/or haemolysis.
• Abdominal palpation
• Reflexes and clonus
• Oedema.

Fetal assessment

• Fetal movement pattern and frequency
• Cardiotocograph (CTG)
• Ultrasound (US) assessment of fetal growth, Amniotic Fluid Index (AFI) and umbilical artery dopplers.

Ongoing management

Practice points

• Management after initial assessment will be based on results of investigations and ongoing blood pressure measurement. 
• Some women referred for assessment of new onset hypertension will have normal blood pressure and investigations: 
  • these women are considered to have transient or labile hypertension 
  • repeat assessment within 3–7 days, as many will subsequently develop pre-eclampsia.

Antenatal care

Practice points

• Aim for BP <150/100 mmHg
• Plan a schedule of antenatal care based on the woman’s individual needs
• Monitor BP as clinically indicated
• Routine CTG not indicated
• 28–30 weeks US for growth
• 30–32 weeks US for growth.

Table 3. Timing of birth for women with gestational hypertension

Intrapartum BP monitoring

• BP <160/110 mmHg – hourly BP measurement
• BP ≥160/110 mmHg – continuous BP measurement.

Intrapartum analgesia

• Consider epidural, as an adjunct to other treatment.

2nd stage

• Plan for instrumental delivery for women with severe hypertension unresponsive to treatment.

Hypertension at booking or <20 weeks gestation

Chronic hypertension: antenatal care and planning for birth flowchart

Antenatal care

Practice points

• Aim for BP <150/100 mmHg.
• Consider antihypertensives when systolic blood pressure persistently exceeds 150 mmHg and/or diastolic pressure exceeds 95 mmHg
• Women taking antihypertensives pre-pregnancy should be changed to first line agents (methyldopa or labetalol) as soon as pregnancy is diagnosed
• Women with chronic hypertension have increased risks of: 
  • accelerated hypertension in the third trimester 
  • superimposed pre-eclampsia 
  • fetal growth restriction 
  • placental abruption, premature delivery 
  • stillbirth.
• Early obstetric review is recommended
• Frequent review by an obstetrician and by a physician familiar with the management of hypertension in pregnancy is recommended
• Benefits of pharmacological treatment of mild chronic hypertension in pregnancy have not been proven
• Possible benefits of treatment include reduction in hospital admission (when hypertension is not due to pre-eclampsia) and prolongation of gestation when uncontrolled hypertension would result in delivery
• Understand your health service’s capability level – see Victorian Maternity and Newborn Capability Framework.
• If transfer is required seek assistance from PIPER – 1300 137 650.

Maternal assessment and investigations

• Ophthalmic examination
• Urinalysis for proteinuria
• Spot urine PCR
• Serum electrolytes
• ECG (if not performed recently)
• 24-hour urine catecholamines if hypertension is severe
• Pre-eclampsia screen if there is a sudden increase in blood pressure or new proteinuria.

Fetal assessment

• 20-week US for morphology
• 26–28 week US for growth
• 28 weeks to delivery: US for growth
• CTG if clinically indicated; for example, abnormal fetal growth, decreased fetal movement, unstable BP.

Birth

• Timing of birth as for gestational hypertension (Table 3)
• Intrapartum monitoring and management as for gestational hypertension.

Hypertension and involvement of organ systems

Pre-eclampsia: assessment and management flowchart

Risk factors

Development of pre-eclampsia generally requires a combination of underlying susceptibility and a triggering event. Susceptibility factors have been identified but no accurate predictive tool has been developed.

Combined first trimester screening for pre-eclampsia risk is offered by some imaging services and includes screening for pregnancy-associated plasma protein-A (PAPP-A), placental growth factor (PlGF), BP, family history and ultrasound. This is estimated to detect approximately eight out of 10 women at risk of developing pre-eclampsia.

Table 4. Pre-eclampsia risk factors

Prevention

Practice points

• Counsel all women with risk factors (Table 4) about the risk factors, symptoms and management.
• Offer women at high risk calcium supplements and low dose Aspirin:
  • 150 mg of Aspirin, nocte, commenced at ≤16 weeks gestation
  • 1.5 g calcium daily.
• Consider offering low dose Aspirin and calcium to women at moderate risk of pre-eclampsia.
• If a woman’s risk of pre-eclampsia is recognised between 16 and 20 weeks, it is still appropriate to commence low dose Aspirin and calcium supplementation
• Understand your health service’s capability level – See Victorian Maternity and Newborn Capability Framework.
• If transfer is required seek assistance from PIPER – 1300 137 650.

Assessment

Maternal assessment

• History – headache, visual disturbances, epigastric or right upper quadrant pain
• Vital signs – BP, pulse, respiratory rate, temperature
• General examination – abdominal palpation, reflexes, clonus.

Investigations

• Spot urine PCR
• Mid-stream urine
• FBE
• UEC
• LFT
• Uric acid.

Fetal assessment

• Fetal movement pattern and frequency
• CTG if >28 weeks
• US for biometry, AFI, Doppler studies, biophysical profile.

Diagnosis

Practice points

Pre-eclampsia can be diagnosed when hypertension arises after 20 weeks gestation and there is one or more of the following signs:

• Renal involvement:
  • significant proteinuria – a spot urine PCR >30 mg /mmol
  • serum or plasma creatinine greater than or equal to 90 micromol/L
  • oliguria <80 ml/4 hours.
• Haematological involvement:
  • thrombocytopenia <100,000 /μL
  • haemolysis: schistocytes or red cell fragments on blood film, raised bilirubin, raised lactate dehydrogenase >600 IU/L, decreased haptoblobin
  • DIC.
• Liver involvement:
  • raised transaminases
  • severe epigastric or right upper quadrant pain.
• Neurological involvement:
  • hyperreflexia
  • convulsions (eclampsia)
  • persistent visual disturbances (photopsia, scotomata, cortical blindness, posterior reversible encephalopathy syndrome, retinal vasospasm)
  • persistent, new headache
  • stroke.
• Pulmonary oedema
• Fetal growth restriction (FGR)

Management

≥37+0 weeks

• Delivery is indicated
• Control BP – see Severe hypertension

<37 weeks

• Control BP – see Severe hypertension
• Prior to delivery:
  • aim for BP <150/100
  • optimise fluid status
  • correct coagulopathy
  • consider MgSO4 - See Administration of magnesium sulfate (MgSO4)
• At ≥34 weeks, do not delay delivery as continuation of pregnancy is associated with risk to the fetus.

<34 weeks

• Control blood pressure – see Severe hypertension
• At <34 weeks delivery should be delayed for 24–48hrs - if fetal and maternal status permit - to allow for administration of corticosteroids.

Practice points

• Pre-eclampsia is a progressive disorder that will inevitably worsen as pregnancy continues.
• Delivery is the definitive management and is followed by resolution over a few days but occasionally longer.
• If delivery is delayed, ongoing regular assessment of maternal and fetal condition is required, with careful daily assessment for clinical symptoms and signs along with regular blood and urine tests as clinically indicated.
• Outpatient management of pre-eclampsia will be appropriate for some women, if their BP is stable, after consultation with a consultant obstetrician.
• Refer women with severe early onset pre-eclampsia to a Level 6 Maternity Service – consult with PIPER as indicated: 1300 137 650.

Onset of seizures in a woman with pre-eclampsia

Eclampsia: management flowchart

Practice points

• Magnesium sulfate (MgSO4) is the recommended first line treatment.
• Eclampsia remains rare in Australia but is the presumed diagnosis in pregnant women who present with a seizure.
• There are no reliable clinical markers to predict eclampsia and, conversely, the presence of neurological symptoms and/or signs is rarely associated with seizures. 
• Seizures may occur antenatally, intra-partum or postpartum, usually within 24 hours of delivery but occasionally later.
• Alternative diagnoses include epilepsy, cerebral venous thrombosis and other medical causes of seizure disorders.
• Diazepam is not an appropriate first line treatment.

Management of eclampsia

Resuscitation

• Ensure a patent airway
• Administer 10 L/min oxygen by mask
• Obtain intravenous access
• Administer magnesium sulfate (MgSO4) IV during or immediately after an eclamptic seizure, with a loading dose of 4 g over 20 minutes
• A prolonged, generalised seizure may be due to other intracerebral pathology, in which case benzodiazepines are appropriate:
  • intravenous diazepam (2 mg/min to maximum of 10mg) 
    or
  • Midazolam (0.1 – 0.2 mg/kg IV or IM).

Prevention of further seizures

• Following resuscitation, continue MgSO4 for 24 hours. 

Control of hypertension

• Aim for BP <160/100 mmHg
• The threshold for further seizures is lowered after eclampsia, likely in association with vasogenic brain oedema
• The danger of cerebral haemorrhage is real.

Fluid restriction

• Nil by mouth
• 80 ml/hr IV crystalloid.

Delivery

• Arrange for delivery once the woman’s condition is stable
• Ensure attendance of senior paediatric clinician
• Ensure continuous CTG monitoring while awaiting delivery
• There is no role for continuation of pregnancy once eclampsia has occurred.

Practice points

• Do not prescribe MgSO4 before discussion with an obstetric consultant.
• MgSO4 therapy is recommended for use antepartum, intrapartum and within the first 24 hours postpartum for severe pre-eclampsia when the following factors are present:
  • persistently elevated BP despite adequate hypotensive therapy and appropriate fluid management
  • evidence of central nervous system CNS dysfunction 
  • thrombocytopenia
  • liver disease.

Dosage and administration

Intravenous

• Loading dose of 4 g IV over 20 minutes
• Maintenance dose of 1 g IV per hour for 24 hours from birth or last seizure
• If there is diagnosed or suspected renal impairment:
  • loading dose of 2 g IV over 20 minutes
  • maintenance dose of 0.5 g per hour IV. 

Intramuscular

• The loading dose of MgSO4 can be administered IM, in the absence of IV access
• 4g IM:
  • 2g into left buttock
  • 2g into right buttock.

MgSO4 levels

• Monitor for signs of magnesium toxicity: 
  • decreased deep tendon reflexes
  • respiratory rate <12 breaths per minute
  • reduced urine output: <40 mL per hour
  • serum magnesium concentration >3.5 mmol/L
• MgSO4 serum levels must be taken:
  • if there are signs of toxicity
  • for women with renal impairment and/or low urine output (<30 ml/hr)
• Serum levels may be taken six-hourly during infusion.

Antidote for magnesium toxicity

• 10 per cent calcium gluconate 10 ml IV.

Maternal observations

• During loading dose:
  • 5-minutely BP, pulse (PR) and respiratory rate (RR)
  • at completion of loading dose, record BP, PR, RR and deep tendon reflexes
  • observe for adverse effects.
• During maintenance dose:
  • hourly BP, PR and RR
  • hourly urine output
  • hourly deep tendon reflexes.
• Maintain an accurate record of fluid balance.
• Before discontinuing MgSO4 therapy:
  • BP should be stable (consistently below 150/100)
  • woman should have adequate diuresis
  • woman should be clinically improved, with no headache or epigastric pain.

Practice points

• HELLP Syndrome is a variant of severe preeclampsia: Haemolysis, Elevated Liver enzymes and Low Platelet count.
• Maternal mortality is reported to be as high as 1–2 per cent.
• Haemolysis is rare, but elevated liver enzymes (ALT, LDH) and thrombocytopaenia are common.
• In a woman with pre-eclampsia, the presence of any one of the following is an indicator of severe disease, even if not suggested on other criteria such as severity of hypertension:
  • maternal platelet count of <100,000 x 109/L
  • transaminase level or LDH more than double the normal upper limit
  • haemolysis of any quantity.

Antenatal management 

• Understand your health service’s capability level – see Victorian Maternity and Newborn Capability Framework.
• If transfer is required seek assistance from PIPER – 1300 137 650.
• Consider platelet transfusion if the platelet count is sufficiently low to present a hazard for operative delivery (consult with consultant haematologist or obstetric physician).
• Service capability level affects blood product availability - see Appendices for blood product availability by capability level.

Postpartum management

• Administer a platelet transfusion if there is significant bleeding attributed to pre-eclamptic thrombocytopenia at any time in the puerperium (consult with consultant haematologist or obstetric physician).

Table 5. Indications for delivery

Practice points

• Daily obstetric review
• 4-hourly observations for 48 hours:
  • vital signs
  • reflexes
  • clonus
• Send the placenta for pathological examination and follow up results
• Enalapril is the preferred antihypertensive agent:
  • 5 mg daily
  • can be used safely by breastfeeding mothers of term infants
  • exercise caution with breastfeeding mothers of preterm infants.
• Hypertension may persist for up to three months and will require monitoring and slow withdrawal of antihypertensive therapy.
• After delivery, all clinical and laboratory derangements of preeclampsia recover, but there is often a delay.
• The woman and her family are often overwhelmed and distressed from their experience and appropriate counselling post-partum should include psychological and family support.
• All women who develop pre-eclampsia and gestational hypertension are at risk of these disorders in future pregnancies and should receive appropriate counselling before embarking upon another pregnancy.

Practice points

• Minimise separation of mother and baby
• Ensure the breastfeeding woman receives accurate information about the potential effects of any medications she is taking
• Observations of baby as per local guidelines, documented on a track and trigger chart 
• Be aware of the increased risk of:
  • prematurity
  • growth restriction (links to Neonatal eHandbook)
  • hypoglycaemia (links to Neonatal eHandbook).

Audit and performance improvement

All maternity services should have processes in place for:

• auditing clinical practice and outcomes
• providing feedback to clinicians on audit results
• addressing risks, if identified
• implementing change, if indicated.

Potential auditable standards:

• women who maintain an antenatal BP <150/100 mmHg
• women at risk of pre-eclampsia who are prescribed low-dose Aspirin and calcium supplementation
• adherence to 4-hourly observations for 48 hours postpartum.

For more information or assistance with auditing, please contact the Maternity and Newborn Clinical Network: maternityehandbook@safercare.vic.gov.au.

References

• Magee, L.A. et.al. (2015) Less-Tight versus Tight Control of Hypertension in Pregnancy. New England Journal of Medicine 372(5), 407-417. doi: 10.1056/NEJMoa1404595
• Monash Health (2017) Hypertensive disorders in pregnancy: Pre eclampsia / eclampsia management – Clinical guideline.
• NICE (2011) Hypertension in pregnancy pathway – Chronic hypertension.
• Poon, LC.. & Nicolaides, K.H. (2014) First-trimester maternal factors and biomarker screening for preeclampsia. Prenatal Diagnosis 34, 618-627. DOI: 10.1002/pd.4397
• Roberge, S., Nicolaides, K., Demers, S., Hyett, J., Chaillet, N. & Bujold, E. (2017) The role of aspirin dose on the prevention of preeclampsia and fetal growth restriction: systematic review and meta-analysis. American Journal of Obstetrics & Gynecology216(2), 110-120.
• Rolnik, D.L. et.al. (2017) Aspirin versus Placebo in Pregnancies at High Risk for Preterm Preeclampsia. New England Journal of Medicine. doi: 10.1056/NEJMoa1704559
• Tranquilli, AL., Dekker, G., Magee, L., Roberts, J., Sibai, BM., Steyn, W., Zeeman, GG. & Brown, MA. (2014) The classification, diagnosis and management of the hypertensive disorders of pregnancy: A revised statement from the ISSHP. Pregnancy Hypertension: An International Journal of Women’s Cardiovascular Health 4, 97-104.

Definitions

Abbreviations

Service capability level and associated blood product availability