Prenatal incidence of isolated right aortic arch and double aortic arch.

Objective: To define the incidence of variants of aortic arch sidedness in fetuses undergoing routine first trimester ultrasound examination.

Methods: The data for this study were derived from prospective routine ultrasound examination at 11 to 13 weeks' gestation in singleton pregnancies examined in a local population between January 2014 and March 2018. We examined the incidence of isolated right aortic arch (RAA) and double aortic arch (DAA) in the local, screened population and compared the groups with and without these abnormalities.

Results: The study population of 33,202 pregnancies included 18 (5.4 per 10,000) cases with isolated RAA and 5 (1.5 per 10,000) with DAA. In the group with isolated RAA or DAA, compared to those without, the median maternal age was higher and the incidence of conceptions from fertilization (IVF) was eight-fold higher. The prevalence of 22q11microdeletion was 5% in patients with RAA from this local population.

Conclusions: The incidence of isolated RAA and DAA in a local population undergoing routine first-trimester ultrasound examination is 2-3-fold higher than that reported in postnatal studies and the risk for these abnormalities is substantially increased in fetuses conceived by IVF.