Syncope toolkit

Syncope is very common and will affect 42% of people during their lifetime

Pregnancy and syncope

Syncope occurs in up to 4.6% of pregnancies. Most women with vasovagal syncope (VVS), orthostatic hypotension (OH) and postural tachycardia syndrome (PoTS) will have a safe delivery and a healthy baby. However, syncope may be associated with slightly higher rates of adverse outcomes including preterm births and congenital anomalies, and an increased incidence of maternal cardiac arrhythmias and syncope in the first-year postpartum.

In this section: 

Causes of syncope in pregnancy

Causes of syncope and low blood pressure in pregnancy include:

  • Vasovagal syncope
  • Pulmonary embolism
  • Haemorrhage eg ruptured ectopic pregnancy, aortic dissection
  • Uterine rupture
  • Amniotic fluid embolism
  • Cardiac causes include peripartum cardiomyopathy, coronary or aortic dissection, SVT, VT
  • Supine hypotensive syndrome (aorto-caval compression)
  • Orthostatic hypotension
  • In relation to PoTS.

Non syncopal causes of blackouts in pregnancy:

  • Hypoglycaemia
  • Eclamptic seizures.

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Risks of VVS, OH and PoTS in pregnancy

Vasovagal Syncope - occasional report of abruption, fetal hypoxia.

Low blood pressure – some small studies suggest a slight reduction in birth weight and increase in stillbirth. Mechanism and management is unclear.

PoTS – pregnancy is safe in PoTS for mum and baby. No increase in miscarriage, preterm delivery, stillbirth or perinatal mortality.

Paternal syncope is not uncommon and is also a risk! Trauma to both mother and father can occur.   

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Supine hypotensive syndrome

Points to consider:

  • This occurs due to aorto-caval compression
  • Within 3-7 minutes, around 30% of the effective circulating blood volume can be effectively lost and significant hypotension occurs
  • Can occur from 19 weeks of pregnancy – when supine
  • Effect on mum: hypotension associated with dizziness, pallor, sweating, nausea, syncope or near syncope, tachycardia (bradycardia in late stages), lower limb oedema
  • Effect on baby: fetal hypoxia or death
  • Management – turn onto left side when supine or sit upright.

Palpitation and Arrhythmias in pregnancy

The majority of arrhythmias in pregnancy are not harmful. However physiological changes in pregnancy may trigger arrhythmias, some of which can lead to syncope.

Benign palpitations – it is normal for heart rate to increase by 25% in pregnancy, and ectopic beats occur in around 50%, and both therefore cause palpitations.

Structural heart disease - this may present for the first time in pregnancy, for example mitral stenosis. In women with known structural heart disease (such as congenital heart disease, acquired valvular disease, cardiomyopathy), arrhythmia is a predictor of a cardiac event during the pregnancy and should therefore be treated as a red flag. Women with structural heart disease may require referral to a tertiary obstetric centre to plan a safe pregnancy and delivery.

Electrical heart disease – such as accessory pathways or Wolff-Parkinson-White, AV-nodal re-entrant tachycardia, channelopathies, drug-related long QT.

Planning a pregnancy with syncope

When planning a pregnancy with syncope, you should:

  • Provide the usual preconception advice
  • Maximize wellness before pregnancy – self-care measures
  • Stop any drugs that are contraindicated - see UKTIS website
  • Counsel the patient regarding the risk and benefit of continuing drugs and seek secondary care consultant advice where appropriate
  • Consider any associated conditions which may impact the pregnancy such as cardiac disease, hypermobile Ehlers-Danlos syndrome, chronic fatigue syndrome and autoimmune conditions
  • Refer to specialist maternity services if syncope is due to a cardiac cause for preconception advice - find out more about cardiac disease and pregnancy from the Royal College of Obstetricians and Gynaecologists.

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Safety in pregnancy of medication used in VVS, OH and PoTS

DrugUse in pregnancyEffectsSafety in pregnancy and breast feeding
Fludrocortisone Addison’s Monitor sodium, potassium and magnesium Safe
Ivabradine Harmful in animals Not safe
Midodrine Limited experience

Gastroschisis (theoretical risk)

No human data

Not recommended - no data

B Blockers: Labetalol


1st line in hypertension

Slight intrauterine growth retardation


B Blockers: Propranolol

Various uses

Slight intrauterine growth retardation Small dose safe            

B Blockers: Bisoprolol

Newer drug Slight intrauterine growth retardation


Pyridostigmine Myasthenia Gravis Safe
Clonidine Pre-eclampsia Like methyl dopa Probably safe
Octreotide Limited data Caution

Table adapted from consensus document 2007.

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Self-care measures for VVS, OH and PoTS in pregnancy

Self-care measures include:

  • High fluid intake (unless contraindicated)
  • Increase salt (unless contraindicated)
  • Compression tights or stockings
  • Some women will improve as pregnancy progresses; this is thought to be related to the 50% increase in plasma volume in late pregnancy.

Labour and delivery

In general the management of the delivery follows normal obstetric guidelines and is not altered by the fact that the patient experiences syncope.

Note that:

  • Upright posture and warm baths should be avoided
  • Squatting may relieve symptoms, but standing up after squatting may exacerbate them.

Anaesthetic considerations

Anaesthetic considerations include:

  • Hypotensive tendency or intraoperative hypotension
  • Epidurals and spinals can be used but can worsen hypotension
  • Early use of intravenous infusion, especially if fasting.

Postnatal period

Things to consider in the postnatal period: 

  • Early mobilisation after delivery
  • Extra fluids when breast feeding
  • Consider compression tights
  • Pacing of activities.

In PoTS, most women report improvement 6-12 months after pregnancy

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    Syncope investigations in pregnancy

    Considerations for syncope investigations in pregnancy:

    • Mostly investigations can wait unless cardiac syncope is suspected
    • Echo, exercise ECG and some pharmacological challenges may be undertaken
    • Active stand test can be undertaken in pregnancy
    • Tilt test is contraindicated in pregnancy
    • Symptom diary and heart rate or blood pressure recordings can be helpful.

    Devices in pregnancy

    Considerations for devices in pregnancy:

    • Insertable Cardiac Monitors (ICMs) are not contraindicated in pregnancy
    • DC cardioversion can be safely administered where necessary throughout pregnancy
    • pacemakers – should be avoided if possible under 40 years old - however, insertion of a pacemaker during pregnancy does not appear to cause maternal or fetal complications
    • women with implantable cardioverter defibrillators (ICDs) have achieved successful pregnancies, even when the devices have been triggered.

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