Throughout the world, heart disease remains the leading indirect cause of maternal death. Many cardiac problems are predictable with knowledge of the mother’s underlying cardiac condition, but cardiac events can occur rapidly and unexpectedly. In the latest Australian maternal mortality review, 20% of maternal deaths occurred during birth or the first 24 hours after delivery. Mortality was higher in older women, Indigenous people, those living in very remote areas and mothers from low socioeconomic groups.¹

Risk stratification

Critical to managing women with heart disease in pregnancy is a careful cardiac assessment, ideally prepregnancy or early in the pregnancy, to gain a complete picture of the type of underlying cardiac abnormality and its severity. Cardiovascular risk has been best classified by the modified World Health Organization (mWHO) classification of maternal cardiovascular risk.^{2 3} This discussion will only consider women at mWHO risk levels 1 and 2 as women at higher mWHO risk require individualised specialist management with a cardio-obstetric team and delivery at a specialised hospital.

Table 1. Modified WHO Criteria I and II.

Multidisciplinary planning for delivery, discussed with the mother, is important to minimise complications. It is essential that this is well documented and immediately available at all times.

Women with underlying heart disease may decompensate rapidly if they develop gestational hypertension or preeclampsia due to the sudden increase in afterload to the heart.

In lower risk women, the mode of delivery should be determined by obstetric indications. Elective caesarean sections for women with cardiac disease are only recommended for women with aortic pathology, severe mitral and aortic valve stenosis, intractable heart failure, pulmonary artery hypertension and for some who are anticoagulated.

Labour may be induced in cardiac women with artificial rupture of the membranes and the use of oxytocin. Misoprostol is usually safe for women with cardiac disease but can cause coronary vasospasm.⁴ The American College of Obstetrics and Gynecology recommends elective induction of labour in pregnant women with cardiac disease between 39 and 40 weeks.⁵

Cardiac ECG monitoring for most low-risk cardiac women is not necessary in labour but for women with a history of arrhythmias it is wise to have ECG monitoring (and medication to treat the arrhythmia) in the delivery room. If cardiac monitoring is planned, it is important that suitably trained staff are available who can interpret the ECG changes and give emergency antiarrhythmic therapy. For women with intracardiac shunts (ASD, VSD) care needs to be taken with peripheral venous lines because of the risk of introducing air emboli that could cross the defect when the mother is pushing, as right heart pressures are significantly elevated at this time. Careful attention to maternal blood pressure and fluid administration is important for all women.

Good analgesia for labour will reduce maternal cardiac stress by reducing maternal tachycardia. Care needs to be taken with the use of epidural analgesia and anaesthesia to minimise sudden falls in maternal blood pressure or volume overload from intravenous fluids given. Use of a continuous epidural and careful fluid management can minimise this and is the preferred approach for cardiac women.

Labouring in the lateral position will improve cardiac return to the heart. The active stages of labour cause many haemodynamic changes increasing right heart pressures, the return of blood to the heart and the need for an increased maternal cardiac output. An assisted delivery will reduce maternal cardiac work but is not usually necessary for low-risk cardiac women.

Antibiotic prophylaxis for the prevention of endocarditis is no longer recommended for delivery in women with valvular heart disease.

Oxytocin given by a slow infusion is the ecbolic of choice. PGE analogues may be given for postpartum haemorrhage but ergometrine and PGF analogues should be avoided due to vasoconstriction.

Major haemodynamic changes continue in the early postpartum period. Mothers should remain in hospital and under close observation over this time.

Managing the unexpected cardiac problems in labour

Women with undiagnosed cardiac problems may present in labour or may deliver after an acute cardiac event.

Myocardial infarction

Acute myocardial infarctions occur 3–4 times more commonly in pregnancy than in an age-matched nonpregnant population. Events occur most commonly postpartum (73%) and in the third trimester (21%).⁶ Risk is increased with the administration of ergotamine causing vasoconstriction, paradoxical emboli where there are atrial or ventricular septal defects or as part of the hypercoagulable state of pregnancy.^{2 4} Important differential diagnoses in a woman presenting with chest pain are aortic dissection and pulmonary embolus. Diagnosis is made predominantly by history, ECG changes and troponin rise with echocardiography and angiography where indicated.

Aortic dissection

An aortic dissection is a medical emergency. With a viable fetus, immediate delivery by caesarean section with repair of the aorta is recommended for Stanford type A dissection (involves ascending aorta) and medical management for Stanford Type B dissection (confined to the descending thoracic aorta).²

Maternal cardiac arrest

A maternal cardiac arrest necessitates immediate resuscitation of the mother and treatment where possible of the underlying cause.⁷

CPR is recommended as for nonpregnant patients with careful attention to airway management to minimise hypoxia and early consideration of delivery by perimortem caesarean section. Maternal survival is significantly improved when delivery is within five minutes of the arrest, but in a series of 57 deliveries following cardiac arrest, maternal survival occurred with delivery at 10.0 + 7.2 mins compared to 22.6 + 13.3 mins in non-survivors of cardiac arrest. Neonatal survival was seen at an average of 14 + 11 minutes from cardiac arrest compared to 22 + 13.3 minutes in non-survivors.⁸

Arrhythmia

All arrhythmias occur more commonly in pregnancy. In an otherwise well woman, SVTs occur most commonly and may complicate delivery. Management is the same as for a nonpregnant woman: with immediate Valsalva manoeuvre and, if unsuccessful, intravenous adenosine as first-line therapy followed by verapamil or metoprolol if unsuccessful. In labour, the goal is to restore normal rhythm promptly to minimise maternal hypotension and fetal compromise.⁹

Rare causes of ventricular tachycardia presenting in labour or immediately postpartum include long QT syndrome. Beta blockers are the drugs of choice for these patients.

There will always be a risk of unexpected complications with cardiac women in labour, but careful assessment of the pregnant woman, labour planning and good communication between the multidisciplinary team will significantly reduce risk and help ensure a good pregnancy outcome for the mother and baby.

1. Australian Institute of Health and Welfare 2020. Maternal deaths in Australia 2015–2017. Cat. No. PER 106. Canberra: AIHW.
2. Regitz-Zagrosek V, Roos-Hesselink JW, Bauersachs J, et al. 2018 ESC Guidelines for the management of cardiovascular diseases during pregnancy. Eur Heart J. 2018;39(34):3165-3241.
3. Roos-Hesselink J, Baris L, Johnson M, et al. Pregnancy outcomes I women with cardiovascular disease: evolving trends over 10 years in the ESC Registry of Pregnancy and Cardiac disease (ROPAC). Eur Heart J. 2019;40:3848-55.
4. Mehta LS, Warnes CA, Bradley E, et al. Cardiovascular considerations in caring for pregnant patients. A scientific statement from the American Heart Association. Circulation. 2020;141:e884-e903.
5. ACOG Practice Bulletin No. 212: pregnancy and heart disease. Obstet Gynecol. 2019;133:e320-e356.
6. Elkayam U, Jainapurkar S, Barakkat MN, et al. Pregnancy-associated acute myocardial infarction: a review of contemporary experience inn 150 cases between 2006 and 2011. Circulation. 2014;129:1695-1702.
7. Jeejeebhoy FM, Zelop CM, Lipman S, et al. Cardiac arrest in pregnancy: A scientific statement from the American Heart Association. Circulation. 2015;132:1747-73.
8. Einav S, Kaufman N, Sela HY. Maternal cardiac arrest and perimortem caesarean delivery: evidence or expert-based? Resuscitation. 2012;83:1191-1200.
9. Bircher CW, Farrakh S, Gada R. Supraventricular tachycardia presenting in labour: A case report achieving vaginal birth and review of the literature. Obstetric Medicine. 2016;9:96-7.