The risk of cardiovascular complications during pregnancy in women with cyanotic congenital heart defects is high, affecting about one third of such women [9, 10]. The most common complication is heart failure, affecting 18.9 % of pregnancies, as reported in the meta-analysis by Drenthen et al. [10]. Other common complications are arrhythmias (4.8 %), endocarditis (4.1 %) and thromboembolic complications (3.6 %). In contrast to cardiovascular complications, obstetric complications seem not to be particularly increased, apart from postpartum haemorrhage, which may be related to coagulation abnormalities and thrombocytopenia, frequently observed in patients with long-standing cyanosis. Nonetheless, the occurrence of obstetric complications, such as hypertensive disorders of pregnancy, pre-eclampsia or multiple pregnancies, increases the haemodynamic load of pregnancy and thus increases the risk of maladaptation and subsequently increases the risk of cardiovascular complications in vulnerable patients [6, 7, 11, 12]. The increased risk of multiple pregnancies may be of particular importance in women seeking assisted fertilisation and underscores the need for optimal multidisciplinary pre-pregnancy communication, counselling and planning.

The occurrence of cardiovascular complications, such as tachyarrhythmias during pregnancy and peripartum may further impair the adaptive capacity of the cardiovascular system and precipitate decompensation. The impact of pregnancy on long-term outcomes in women with cyanotic heart defects is not well defined. Pregnancy may, however, lead to worsening of functional capacity [9].

Based on data from lesion-specific outcome series and multicentre studies, the risk of adverse fetal events is extremely high in women with unrepaired cyanotic defects [6, 7, 9]. About half of pregnancies end in spontaneous abortion [9]. In on-going pregnancies beyond 20 weeks of gestation the risk of premature delivery is more than 40 % and two thirds of babies are born small for gestational age [10]. Prematurity can result from spontaneous premature labour but also from early, induced delivery for maternal (cardiac) reasons. For women with cyanotic congenital heart defects, the risk of having a stillbirth is among the highest in all congenital cardiac defects. The high rate of offspring outcomes is illustrated in Fig. 16.3a, adapted from the study of Presbitero et al. [9]. As illustrated in Fig. 16.3b, the risk of fetal complications is strongly predicted by the severity of cyanosis. The fact that women with resting oxygen saturations below 85 % have a very low chance of delivering a viable offspring may have an important bearing on pregnancy counselling and pre-pregnancy optimisation of the underlying cardiac condition.

Apart from the maternal cardiac condition, the risk for offspring events is also determined by obstetric risk factors, such as maternal age, multiple gestations, history of premature delivery or rupture of membranes, incompetent cervix or antepartum bleeding and placental abnormalities [13]. This underscores the need for a multidisciplinary team approach not only during pregnancy but for pre-pregnancy risk assessment and counselling as well.

The recurrence risk of isolated congenital heart defects in the offspring ranges on average between 3 and 5 % [14]. There is however substantial variability in recurrence risk, depending on familial occurrence and type of defect [15, 16]. Some congenital heart defects that may be encountered in women with unrepaired cyanotic defects (i.e. pulmonary atresia or tetralogy of Fallot) are associated with the 22q11 microdeletion syndrome. The inheritance of the 22q11 microdeletion syndrome is autosomal dominant, and recurrence risk is thus 50 %, with a high risk of congenital cardiac defects (particularly conotruncal defects) in the affected offspring.

Women with unrepaired cyanotic heart defects may be prone to develop heart failure, as many have diastolic ventricular dysfunction and may not tolerate the increasing volume load of pregnancy. Serial measurements of natriuretic peptides (Pro-BNP or BNP) may help in diagnosis and risk stratification of heart failure during pregnancy [19, 20].

In women with unrepaired cyanotic heart defects, heart failure may present with worsening cyanosis, as shifts in the balance between systemic and pulmonary vascular resistance may precipitate increased right-to-left shunting. For these women, the mainstay of therapy is bed rest to reduce further exacerbation of cyanosis triggered by physical activity.

If overt heart failure occurs, patients should be admitted to a specialised centre, and precipitating factors, such as infection or arrhythmias, should be actively sought and excluded. Bed rest, supplemental oxygen and careful fluid balance with daily weight measurements should be initiated. Careful administration of diuretics may be used but with caution to avoid overdiuresis which can reduce uteroplacental blood flow.

In the case of refractory heart failure, delivery should be contemplated as soon as the fetus is viable, or, in the case of persistent haemodynamic instability, irrespective of the duration of gestation. Antenatal steroids to improve fetal lung maturity may lead to maternal fluid retention and worsening of heart failure.

There are no data on whether vaginal delivery or Caesarean section is superior in women with cyanotic heart defects. Depending on the type of defect, myocardial function and residual haemodynamic lesions, women with cyanotic heart defects may have limited cardiovascular reserves to cope with the haemodynamic needs of labour and delivery. Effective analgesia and assisted second stage of delivery can effectively decrease the additional haemodynamic load of labour. Assisted delivery may however be associated with a higher risk of postpartum haemorrhage and high-degree lacerations [21]. The average blood loss during vaginal delivery of 500 ml counteracts the impact of autotransfusion from the contracting uterus at stage 3 of delivery. Blood loss with Caesarean section is usually higher (on average 1,000 ml) which may be a disadvantage in women for whom (relative) anaemia may be deleterious.

A multidisciplinary delivery plan, based on local experience, logistics and infrastructure (e.g. possibilities for monitoring on labour ward), should be developed early in all women with cyanotic heart defects. Given the high rate of premature delivery, this detailed delivery plan must be available and easily accessible as soon as the fetus is viable. Early involvement of experienced obstetric anaesthetists and, if required, the input of cardiac anaesthetists are vital. Important aspects that need to be covered by the delivery plan are summarised in Table 16.2. A schematic drawing of the patient’s cardiac anatomy is always helpful and may be of critical importance if emergency central venous line or temporary pacemaker insertion is required in women with unusual systemic venous anatomy. It is wise to ensure that air bubble filters are easily available on the labour ward.