Cardiac defects in 1st-trimester fetuses with trisomy 18
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J A Hyett1, G Moscoso, K H Nicolaides
1Harris Birthright Research Centre for Fetal Medicine, Kings College Hospital Medical School, London, UK.
Insights
Trisomy 18 fetuses show a 100% incidence of cardiac defects, including common ventricular septal defects and valvular abnormalities. These findings in early pregnancy offer insights into fetal development and potential diagnostic markers.
Area of Science:
- Medical Genetics
- Fetal Cardiology
- Developmental Biology
Background:
- Trisomy 18 is associated with a high incidence of cardiac defects in neonates, stillbirths, and infants.
- Early detection of trisomy 18 at 11-14 weeks gestation allows for examination of cardiac defects during the first trimester.
Purpose of the Study:
- To determine the incidence and types of cardiac defects in first-trimester fetuses with trisomy 18.
- To investigate potential mechanisms linking cardiac abnormalities to increased nuchal translucency in trisomic fetuses.
Main Methods:
- Pathological examination of hearts and great vessels in 19 fetuses with trisomy 18.
- Karyotype diagnosis via chorionic villus sampling in pregnancies with increased fetal nuchal translucency.
- Examination conducted after termination of pregnancy at 11-14 weeks gestation.
Main Results:
- All 19 trisomy 18 fetuses exhibited cardiac defects.
- Ventricular septal defects (84%) and valvular abnormalities (84%) were the most common defects.
- Hypoplastic aortic isthmus or pulmonary trunk occurred in 10 cases (53%), and persistent left superior vena cava in 6 cases (32%).
Conclusions:
- First-trimester trisomy 18 fetuses have a high frequency of cardiac defects, similar to affected neonates.
- Valvular abnormalities and great vessel hypoplasia may contribute to increased nuchal translucency.
- Persistent left superior vena cava might be linked to head and neck venous congestion.
Abstract:
In trisomy 18, echocardiographic studies of affected neonates and pathological studies of stillbirths and infants have demonstrated a high incidence of cardiac defects. Fetal trisomy 18 can now be detected at 11-14 weeks of gestation, providing the opportunity to examine the incidence of cardiac defects at this gestational age. In 19 fetuses with trisomy 18 pathological examination of heart and great vessels was carried out after termination of pregnancy at 11-14 weeks of gestation. The abnormal karyotype was diagnosed by chorion villus sampling in pregnancies with increased fetal nuchal translucency thickness. All 19 fetuses had cardiac defects, and the commonest were ventricular septal defects in 16 (84%) and valvular abnormalities in 16 (84%). In 14 of the 16 cases with valvular abnormalities more than one valve was affected. The great vessels were available for examination in 18 of the 19 cases, and in 10 there was a hypoplastic aortic isthmus or pulmonary trunk. In 6 (32%) cases there was persistence of the left superior vena cava. In 1st-trimester fetuses with trisomy 18, the frequency of perimembranous ventricular septal defects and valvular abnormalities is similar to that in affected neonates. Haemodynamic changes due to the valvular abnormalities, especially imperforate valves, and hypoplasia of the great vessels may be the underlying mechanisms for the increased nuchal translucency of trisomic fetuses. Persistence of the left superior vena cava may result from venous congestion of head and neck.