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Pregnancy in Women with Complex CHD

Pregnancy in Women with Complex CHD

I distinctly remember the first time I met a patient with congenital heart disease (CHD) – It was during my first year of clinical school, while I was on medical take. She was a pregnant lady in her mid-20s with a Fontan circulation. The medical registrar and I had to whip out our phones to Google ‘Fontan circulation’ and as I did, many questions ran through my mind. Surely this is a high-risk pregnancy? Is her body going to be able to cope with the extra demands of carrying a developing foetus? Is her baby at an increased risk of CHD? This encounter led me to think that the greatest challenge in CHD is the management of pregnancy in women with complex CHD (as defined Bethesda conference).

Major advances in the treatment of CHD have led to an increase in the survival of patients with complex CHD, with many living till child-bearing age and beyond. The challenge really starts when patients reach child-bearing age. Maternal risk assessment can be carried out in a number of different ways – common ones include the ZAHARA score, CARPREG index, and the modified World Health Organisation (mWHO) classification. Several studies have suggested that the mWHO classification is the best at predicting maternal cardiac and birthing complications. This may be because the mWHO classification is the only risk score that takes into account the specific heart condition and clinical cardiac status of patients, and includes other key conditions like pulmonary hypertension.  Pre-pregnancy counselling goes beyond maternal risk assessment – factors that need to be discussed include contraception, optimisation of medication to reduce risk of congenital malformations produced in an embryo or foetus, genetics of CHD, foetal and neonatal risks, and the mode and timing of delivery.

If a patient with complex CHD falls pregnant, intensive monitoring will be required. During pregnancy, the body undergoes various changes to the flow of blood to different organs, in order to accommodate the increased bodily demands of foetal growth and development. Patients with complex CHD need to be managed by a multi-disciplinary team, with regular reviews at an experienced specialist centre. This may be particularly difficult for patients who have limited access to healthcare due to various barriers like geographical distance or financial constraints. 

Foetal echocardiography (using ultrasound waves to analyse the action of the heart) is recommended during the second trimester, as there is a 3-50% risk of the child being born with a heart condition also. Prenatal diagnosis offers parents a chance to learn about treatment options, it also improves neo-natal outcome. Despite foetal echocardiography being the crucial tool for detecting CHD, it is far from perfect. There are no clear guidelines about which measurements are required under these circumstances. Overall, foetal echocardiography can be described as 99.9% specific, but only a moderate accuracy which varies according to the echocardiographic equipment and operator. Therefore, even with foetal echocardiography, a significant number of CHD cases may still be missed. When foetal CHD is diagnosed, it may be difficult to advise patients on treatment options. As the field of foetal treatment is still in its early days and evolving, few randomised controlled trials exists to assist with the recommendation of treatment. Moreover, such treatments are only available at limited specialised centres, which may not be accessible to all patients.    

The timing and mode of delivery is yet another hurdle – it involves a careful balancing act between the risks of the mother and the child (e.g. the cardiac status of the mother versus foetal maturity). The large number of variables that need to be considered along with ethical challenges involved, mean that well-designed trials, and consequently standardised guidelines, do not exist. Ruys et al. used data from the Registry of Pregnancy and Cardiac disease to investigate the relationship between mode of delivery and pregnancy outcome in 1,262 women with cardiac disease (with CHD being the most prevalent cardiac disease at 66%). The authors concluded that planned caesarean section did not have any advantage over planned natural delivery in terms of maternal outcome; those with planned natural delivery in which emergency caesarean section had to be performed had similar outcomes to those with planned caesarean section. However, the baseline characteristics of the planned caesarean group were different, and included more high-risk cases, making the conclusion of the study far less reliable. 

Regardless of the timing and mode of delivery, the time during, and immediately after the birth are challenges in themselves. These periods involve significant changes in the flow of blood, close monitoring and special considerations are needed, when it comes to anaesthesia for example. 

For many, pregnancy is a beautiful experience. For patients with complex CHD, this ‘miracle’ comes at a higher price. Pregnancy in patients with complex CHD demands meticulous planning by a multidisciplinary team from before conception to after delivery, with each phase involving different challenges. Adult patients with CHD form a diverse group of patients, which makes it difficult to build an evidence base and conduct studies that can be applied to CHD on a whole. For complex CHD, such as patients with Fontan repair, the evidence base available is currently restricted to case reports and there is little information on the longer term impact of pregnancy. As more CHD patients reach adulthood, more data will be available to help us fine-tune the management of this group of patients. Hopefully this, along with further advances in midwifery, cardiovascular, foetal and neonatal medicine, what I feel to be the greatest challenge in CHD will be less of a challenge in time to come.   

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