ANTENATAL SURVEILLANCE IN HIGH-RISK FETAL CARDIAC DISEASE: FREQUENCY, RESULTS AND RELATIONSHIP WITH SURVIVAL

Certain congenital heart diseases (CHDs) are associated with a high risk of intrauterine fetal demise (IUFD) and post-natal death, including Ebstein's anomaly, tetralogy of Fallot with absent pulmonary valve and cardiomyopathy. Established obstetric guidelines that recommend frequent antenatal surveillance (AS) of fetal wellbeing in the case of specific maternal and fetal risk factors do not currently include fetuses with high-risk CHD. We sought to establish whether frequent antenatal surveillance could improve fetal outcomes in high-risk fetal CHD and if surveillance results are predictive of outcomes in this setting. We hypothesized that fetuses with high-risk cardiac lesions would benefit from frequent AS and that outcomes would be poorer where surveillance results were abnormal.

We undertook a single center, retrospective review of 61 pregnancies with high-risk fetal CHD diagnosed from 2006-2020. Data pertaining to frequency and results of AS were collected. AS was conducted using the biophysical profile score, non-stress testing and/or fetal echocardiogram. Where possible, the cardiovascular profile score (CVPS) was calculated retrospectively. Frequent surveillance was defined as at least weekly fetal wellbeing testing commencing by 28-32 weeks gestation, or from later diagnosis, until delivery. Outcome measures included survival and mode of delivery. Chi-square testing, or Fisher's exact where numbers were small, were used to determine statistical significance. Antenatal surveillance results were abnormal in 18% (10/56) of pregnancies carrying a fetus with high-risk CHD. There was a trend toward survival at last follow up when AS results were normal (72%, 33/46) compared to those in which surveillance results were abnormal (40%, 4/10), p 0.07. Where AS results were abnormal, significantly more had emergency caesarean sections for fetal indications (7/10 (70%), vs. 2/46 (4%), p < 0.001). IUFD occurred in 20% (2/10) of cases where AS results were abnormal, compared to 7% (3/46) of cases where surveillance results were normal, p 0.21. Where AS was infrequent, IUFD occurred in 13% (4/30), compared to 3% (1/31) where surveillance was frequent, p=0.20. A final CVPS of ≤7 carried a significantly higher mortality rate (11/21, 52%) than a score of ≥8 (6/31, 19%), p 0.01.

Abnormal AS results and/or a CVPS of ≤7 may identify compromised fetuses with high-risk cardiac lesions who could benefit from altered management or expedited delivery. Given the high rates of abnormal surveillance results in this population, frequent surveillance should be considered. A larger trial is warranted to establish whether this leads to a reduction in fetal demise.