In women with Fontan circulation, there is a higher risk of fetal and neonatal adverse events (Tables 15.1 and 15.2). The fetus is at risk of miscarriage, intrauterine growth retardation and prematurity. If the mother is cyanotic, this risk is even higher [5]. In addition, maternal drug therapy may adversely affect the fetus; the most common of these are oral anticoagulants [6] and beta-blockers [7]. The high incidence of miscarriage could be also the effect of ovarian dysfunction and pelvic venous hypertension. The most common neonatal complications are prematurity and small for gestational age birthweight [8–10]. Different causes may account for this: (a) obstetric complications such as premature rupture of membranes and preterm labour, (b) the limited ability of the heart after a Fontan operation to increase cardiac output and cope with the increased demands of pregnancy and delivery, and (c) the decreased placental oxygen delivery and poor neonatal outcome in a cyanotic patient. In any case, premature delivery is a leading cause of infant morbidity and mortality. Growth of the fetus should be monitored frequently throughout pregnancy.

Despite the severe complexity of mother’s heart condition, the overall incidence of congenital heart disease (CHD) in the children is not high (5.6 % and 6.9 %, respectively, in the French and Mayo Clinic series). Furthermore, when CHD recurs, it does not need to be severe (overall one case with the single ventricle, one with the left superior vena cava, one with the patent ductus arteriosus and one with the membranous ventricular septal defect) [9, 10]. However, all pregnant patients with Fontan circulation should be offered a detailed fetal echocardiogram at 16–23 weeks of gestation.

Maternal complications are low in a well-functioning Fontan patient. In the largest series of pregnant women with Fontan operation published to date (59 pregnancies in 37 patients from a multicentre French study [9]; 70 pregnancies in 19 patients from the Mayo Clinic’s experience [10]), there have been no reported maternal deaths; medical issues with earlier pregnancies were not always predictive of difficulties with later pregnancies in the multiparous women. Although there is a risk of maternal morbidity, most complications are treatable (Table 15.1).

The most common cardiac complication reported is a supraventricular arrhythmia. Past medical history of arrhythmia was significantly predictive of atrial arrhythmia during pregnancy, while no association was found with the type of palliation, although review of the literature indicates that the type of Fontan palliation may play a role in arrhythmia genesis during pregnancy [8]. The mechanism behind this complication involves scar tissue formation in the right atrium, damage to the sinoatrial node during previous atriotomy and exposure of the right atrium tissue to elevated pressures. In addition, pregnancy increases plasma volumes, and elevated levels of oestrogen and progesterone cause augmentation of adrenergic receptor activity. Atrial arrhythmias are considered to be a medical emergency and are notoriously resistant to pharmacological therapy. Hence, electrical cardioversion is often required. In this case, the fetal heart rate should be checked before and after for the risk of fetal bradycardias. However, energies of up to 300 W/s have been used without affecting the fetus or inducing premature labour. Recurrent arrhythmias may be managed with catheter ablation using CARTO navigation system without fluoroscopy in tertiary ACHD centres [11].

Physiological changes related to pregnancy may worsen the mother’s functional capacity and symptoms of heart failure [12], particularly those with morphological right ventricles [13], who, when compared to patients with a left ventricle, are more prone to failure. As a result, there is a high incidence of miscarriage, prematurity and intrauterine fetal growth retardation. Depending on the woman’s clinical status, in-patient bed rest, oxygen supplementation and medical treatment of arrhythmia (diuretic, etc.) should be considered, especially during the third trimester.

Thromboembolic complications are possible in patients with the Fontan circulation. However, in the largest series, the incidence was low, three cases in 59 pregnancies, two during the antepartum period and one during the peripartum, and there were no thromboembolic complications amongst 70 pregnancies from the French and American experience [9, 10]. One can speculate, if these lower complication rates may be at least in part due to the anticoagulation/antiplatelet therapy and the lower thrombotic profile of TCPC, present in the majority of the younger pregnant women with the Fontan circulation.

Obstetric complications appear to be a major problem of pregnancy in the context of Fontan palliation: miscarriages with higher rates observed in cyanotic patients, preterm rupture of membranes, premature labour and delivery between 26 and 33 weeks and postpartum haemorrhage are the most common complications. Although these complications do not lead to maternal mortality, they pose a major morbidity and mortality risk to the fetus.

The duration of gestation period is often reduced in women with a Fontan circulation (between 26 and 36 weeks) due to preterm rupture of membranes, premature labour and delivery [8–10]. Monitoring should focus on early signs of heart failure, arrhythmia, thromboembolic complications and worsening cyanosis. Serial echocardiograms are needed to assess overall ventricular size and function and valve gradients and determine any changes, which may influence delivery plans. In this phase, Fontan patients should limit strenuous exercise, obtain adequate rest and be advised against lying flat during pregnancy to avoid aortocaval compression (rolling from the supine to the left lateral position increases the stroke volume and cardiac output). Depending on the individual’s clinical status, in-patient bed rest and oxygen supplementation may be considered during the third trimester.

The cardiovascular system is affected by pain, uterine contractions, medications, maternal position and type of delivery. The timing and mode of delivery and anaesthesia may be selected according to the specific clinical scenario; in general it should be agreed after a multidisciplinary case discussion including the patient. Vaginal delivery is preferable because it is associated with less blood loss, less risk of infection and fewer thromboembolic events [14]. However, it should be undertaken at institutions where there is considerable experience in neuraxial blockade and assisted vaginal deliveries. It is important to ensure good control of pain and anxiety to minimise any further increase in cardiac output. This is achieved using regional techniques, intravenous pain medications and other non-pharmacological techniques [15]. From a haemodynamic point of view, the uterine contractions result in a further increase in cardiac output by up to 60 %, and after immediately delivery, stroke volume increases due to autotransfusion of uterine blood and enhanced venous return following relief of vena cava obstruction [7, 16].

There is no consensus regarding absolute contraindications to vaginal delivery, but Caesarean section is reserved for obstetric indications and for patients in severe heart failure [15]. Delivery by Caesarean section does provide the benefits of minimising the deleterious cardiovascular effects caused by repeated Valsalva manoeuvres and the increases in positive intrathoracic pressure required to achieve a vaginal delivery. Furthermore, a delivery should be scheduled at the time when maximum clinical support is available, which is more difficult to arrange in the case of an attempted vaginal delivery. Maternal monitoring during labour and delivery is obviously necessary and usually includes continuous electrocardiographic, blood pressure monitoring and pulse oximetry and occasionally invasive blood pressure recording. It is important to avoid dehydration, which may reduce central venous pressure and blood flow through the cavopulmonary connection to the lungs. With adequate hydration in combination with the use of compression stockings, it is also possible to minimise the risk of thrombotic events during labour and delivery.

The immediate postpartum period is the third phase and also a potentially high-risk period. It is characterised by further 30 % increase in cardiac output. Despite an estimated 500–1,000 mL of blood lost during delivery, blood volume expands as a consequence of the loss of the placental circulatory bed and the contracting uterus. Hence, there is a risk of cardiac decompensation up to 1 week postpartum. Oxytocin should be infused at the slowest effective dose in such patients because it can produce significant vasodilation and hypotension, which may result in devastating cardiovascular consequences in single ventricle patients [17].

Patients with good function of the Fontan circulation usually do not need regular/chronic medications, with the exception of anticoagulation/antiplatelet therapy. However, if the patient with single ventricle physiology is optimised with cardiac drugs, these medications should be continued throughout pregnancy, but the lowest possible effective dose should be applied. The use of various cardiovascular drugs during pregnancy has been recently and comprehensively reviewed [18–20]. With the exception of heparin, almost all cardiovascular medications can be expected to cross the placental barrier. Whenever possible, medications with the lowest-risk profile should be used for the management of cardiac disease during pregnancy. Commonly used cardiac medications that can have detrimental effects on the fetus or neonate include warfarin, angiotensin-converting enzyme inhibitors and angiotensin receptor blockers. Timing of exposure may be important, and risks and benefits of the medications for the mother need to be considered.

Due to lack of evidence that infective endocarditis is related to vaginal or Caesarean section, antibiotic prophylaxis is not generally recommended by the American Heart Association (AHA)/American College of Cardiology (ACC) or European guidelines [20, 21]. Nevertheless, antibiotic prophylaxis is helpful at the time of delivery for repaired single ventricle patients. These patients are considered to be at risk because of the prosthetic material used in the procedure; further the presence of a shunt increases the risk of a paradoxical septic embolism [17].

Patients with the Fontan operation are at increased risk of intracardiac thrombus formation with a reported incidence ranging from 17 to 33 % [22, 23]. This risk is due to a combination of factors, including the existence of prosthetic material, increased risk of atrial arrhythmia and low cardiac output resulting in a low-flow prothrombotic state [24]. In addition, there is evidence that single ventricle physiology is associated with a baseline deficiency in anticoagulant factors, such as antithrombin III and proteins C and S. However, this finding may be balanced by an equivalent deficiency in procoagulant factors [25]. Overall, there remains controversy regarding the need for routine anticoagulation in all patients following Fontan surgery. Some groups, such as patients with a history of thrombosis, low cardiac output, arrhythmias, atrial dilation and original right atrium-pulmonary artery connection, are more routinely anticoagulated. A randomised trial suggested that aspirin is as effective as coumadin in preventing thrombotic events. However, despite full anticoagulation, thromboembolic events may still occur in these patients [26]. As showed by Tomkiewicz-Pajak et al. patients with a Fontan circulation, despite having significantly reduced platelet numbers, have increased basal platelet activity, increased thrombogenesis, endothelial dysfunction and evidence of systemic inflammation. Although these data support the use of antiplatelet therapy in the same study, a significant proportion of aspirin-treated adults with a Fontan circulation were resistant to aspirin, which may account for the inability of aspirin to prevent thrombotic complications in these patients [27]. Pregnancy itself intensifies the risk of venous thromboembolic complications, with an estimated eightfold increase, which rises to 11-fold during the peripartum period [28]. Therefore, despite the lack of solid evidence, pregnant women with Fontan circulation should be considered for some form of antithrombotic therapy, either full anticoagulation with low molecular weight heparin in higher thrombotic risk patients, prophylactic weight-adjusted low molecular weight heparin (owing to the teratogenic effects of coumadin) or aspirin. The last can be used either in isolation or combined with anticoagulant agents but should be stopped at 35 weeks of gestation.