Prenatal Diagnosis of Aortopulmonary Window in a Twin Pregnancy: Case Report and Review of the Literature

ABSTRACT

Antenatal diagnosis of aortopulmonary window, a rare congenital heart defect, is crucial for timely surgical intervention and prevention of heart failure.

Foetus B at 26 weeks: Doppler echocardiographic imaging demonstrating blood flowing from the pulmonary artery to the aorta.

1. Introduction

Aortopulmonary window (APW) is a rare congenital malformation characterized by a communication between the ascending aorta and the common trunk of the pulmonary artery above the semilunar valves [1]. It accounts for about 0.15%–0.6% of cardiac malformations [2, 3]. At birth, it leads to a left‐to‐right shunt, varying in severity depending on the size of the window and the ratio between pulmonary (RVP) and systemic (RVS) vascular resistances, resulting in heart failure and pulmonary artery hypertension in the newborn. Prenatal diagnosis is crucial, as early surgical correction is typically required to avoid congestive heart failure due to pulmonary overcirculation. Phenotypic discordance in monozygotic twins, who are genetically identical, highlights the role of epigenetic and environmental factors in disease development [4]. The isolated occurrence of a major cardiac malformation such as an APW in only one fetus of a monochorionic diamniotic twin pregnancy is exceptional and raises questions about the epigenetic or developmental mechanisms that may lead to such a phenotypic discordance between monozygotic twins. The identification of a severe cardiac anomaly in only one monozygotic twin challenges the assumption of uniform developmental pathways and emphasizes the importance of individualized monitoring and counseling, even in genetically identical fetuses.

We report a case of an APW diagnosed by prenatal ultrasound during the early third trimester in one of the fetuses of a monochorionic diamniotic twin pregnancy.

2. Case History

Our patient is a 30‐year‐old woman, gravida 2 and para 1, carrying a spontaneous monochorionic diamniotic twin pregnancy. The first pregnancy was uncomplicated. She was referred to our institution at 20 weeks of gestational age (GA) for the monitoring of her twin pregnancy. The ultrasound examination was normal for gestational age with symmetrical growth of both twins. Noninvasive prenatal testing (NIPT) was not performed, in accordance with the patient's preference.

During the follow‐up ultrasound at 25 weeks and 4 days, the cardiac examination of twin B revealed a communication between the aorta and the pulmonary artery in the three‐vessel view (Figure 1) and color Doppler. The diagnosis was supported by sagittal and oblique views of the great vessels showing a direct communication between the ascending aorta and the main pulmonary artery, consistent with a defect in the aortopulmonary septum. The other cardiac structures appeared normal; the four‐chamber view was normal, without ventricular asymmetry. Prenatally, the color Doppler showed blood flows in only one direction, from the pulmonary artery to the aorta (Figure 2). The rest of the morphological study of twin B was unremarkable. The growth and vitality of the fetus were satisfactory. The ultrasound examination of twin A showed no cardiac or extracardiac anomalies. A fetal echocardiogram was performed by a reference pediatric cardiologist at 26 weeks of gestation, which validated the antenatal diagnosis specifying a type II APW.

FIGURE 1.

Foetus B at 26SA: three‐vessel fetal echocardiographic view showing an abnormal pulmonary artery connection with the aorta. (A, aorta; APW, aortopulmonary window; P, pulmonary artery; VC, vena cava.)

FIGURE 2.

Foetus B at 26 weeks: Doppler echocardiographic imaging demonstrating blood flowing from the pulmonary artery to the aorta.

3. Investigations and Treatment

The patient was transferred at 30 weeks to a tertiary centre for follow‐up and delivery, where cardiac surgery could be performed almost immediately after birth. The twins underwent bimonthly follow‐ups, including biometric assessment and Doppler ultrasonography at each visit. No other anomalies were discovered during these follow‐ups. During the third trimester, a 12%–14% weight discrepancy appeared between the twins, probably due to placental sharing in favor of twin B with the cardiac anomaly. Estimated fetal weights were at the 9th percentile for Twin B and the 2nd percentile for Twin A. Doppler measurements remained normal.

The patient gave birth spontaneously vaginally at 35 weeks and 1 day. The first twin (B), carrying the APW, was born with a weight of 2290 g and an Apgar score of 9/9/9. No resuscitation was required. Twin A was born with a weight of 1790 g and an Apgar score of 7/9/9. Both were admitted to the neonatal intensive care unit (NICU). Postnatal echocardiography confirmed APW type II (6–7 mm diameter), according to the Mori classification. Postnatal ultrasound also revealed an abnormal implantation of the right coronary artery (ARCAPA), which arose from the pulmonary trunk instead of the aorta. Twin B remained in the open air for 10 days. She then required continuous positive airway pressure (CPAP) due to the development of pulmonary overload detected on Doppler ultrasound by an increased pulmonary (RVP)/systemic (RVS) vascular resistances ratio, but no drug treatment was required. One month after birth, the patient underwent surgical repair of the aortopulmonary window with reimplantation of the right coronary artery (ARCAPA). The right coronary artery was re‐implanted into the aortic root using polypropylene sutures. The APW was closed on the aortic side with a glutaraldehyde autologous pericardial patch and on the pulmonary side with an autologous pericardial patch. Postoperative echocardiography on Day 4 showed no evidence of residual flow between the aorta and pulmonary artery. This surgical approach is consistent with current practices described in recent literature for the repair of APW. For instance, Reddy et al. [5] reported excellent early and long‐term outcomes. The postoperative course was uneventful, and the baby was discharged from the hospital two weeks after the operation without further treatment. She is currently undergoing routine biannual follow‐ups, which remain entirely reassuring, with harmonious growth and satisfactory neurodevelopmental progress.

4. Conclusion

This case illustrates the value of foetal echocardiography in identifying rare congenital heart defects such as an APW and stresses the importance of assessing associated anomalies, especially coronary artery abnormalities. Early detection supports timely planning and risk stratification. Collaborative efforts among obstetricians, foetal medicine specialists, and pediatric cardiologists are essential in providing comprehensive care for these complex cases.

5. Discussion

Although monozygotic twins originate from the same oocyte and are genetically identical, numerous cases of discordance in congenital anomalies have been reported, affecting both phenotype and genotype [4]. The prevalence of congenital malformations in monochorionic diamniotic (MCDA) pregnancies (10.7%) is twice as high as in dichorionic diamniotic pregnancies and three times higher than in singletons. In 80% of cases, these malformations affect only one of the twins [4, 6]. According to Machin [7], these discordances could be caused by post‐zygotic mutations such as X‐inactivation or chromosomal mosaicism. Other theories have been proposed, including epigenetic phenomena, environmental factors, mutations in mitochondrial DNA, chromatin remodeling, or posttranslational protein modifications [4, 8]. Cardiac malformations are frequently found in monochorionic twin pregnancies [4]. The management of twin pregnancies involving one malformed twin is complex due to the increased risks of premature birth, intrauterine demise (IUD), and potential risks to the healthy twin. In MCDA pregnancies, the in utero death of one twin leads to a 10%–25% risk of fetal death in utero for the other twin and a 25%–45% risk of neurological sequelae [4]. Therefore, ultrasonographic study is essential to detect malformations antenatally.

The APW results from partial agenesis of the aortopulmonary septum during embryogenesis between the 5th and 9th weeks [9, 10]. The defect, which does not involve the aortic or pulmonary valves, can range in size from a few millimeters to several centimeters. Mori proposed a classification in 1978 [9], distinguishing three types: Type I is located between the ascending aorta and pulmonary trunk, just above the semilunar valves; Type II arises in the distal ascending aorta, near the root of the right pulmonary artery; and Type III, the most severe form, involves most of the ascending aorta [10].

The APW may be isolated or associated with various cardiac and extracardiac anomalies [11], including septal defects, interrupted aortic arch, persistent ductus arteriosus, valvular stenoses, Tetralogy of Fallot, transposition of the great vessels, and coarctation of the aorta [3]. Its pathogenesis resembles that of a large persistent ductus arteriosus or a ventricular septal defect. Clinically, it presents as a left‐to‐right shunt. After birth, due to the defect between the aorta and the pulmonary artery, the lung is subjected to increased blood flow and volume, leading to pulmonary arterial hypertension and heart failure, which is initially reversible. If uncorrected, this can progress to Eisenmenger syndrome. Early prenatal diagnosis is critical to guide perinatal care. The prognosis is favorable in isolated cases with timely surgery, whereas without repair, first‐year mortality reaches 40% [10]. Outcome depends on associated anomalies and the timing of surgical intervention [2, 10].

In our case, the observed malformation is associated with an anomaly in the implantation of the right coronary artery. The abnormal origin of the right coronary artery from the pulmonary artery (ARCAPA) is very rare with an incidence of 0.002% in patients undergoing coronary angiography [12]. Patients with ARCAPA are generally asymptomatic and are diagnosed during cardiac evaluation for other issues. Symptoms, although rare, may include dyspnoea, fatigue, congestive heart failure, angina, and even sudden cardiac death [13]. ARCAPA is isolated in most cases, but 40% of patients have an associated malformation. APW is the most common associated congenital lesion. To our knowledge, no cases of prenatal diagnosis are reported in the literature.

In their 2017 review, Tongprasert et al. [14] reported that most prenatally diagnosed APW were type I (80%), with over half associated with major cardiac anomalies such as interrupted aortic arch and Tetralogy of Fallot. While diagnosis was most commonly made in the late second or third trimester, a significant proportion of cases were identified as early as midpregnancy. Although surgical outcomes were generally favorable, approximately 25% of neonates developed cardiac failure, sometimes resulting in death. Building upon this earlier work, we conducted an updated review of the literature from 2017 to 2025 (Table 1), identifying 37 antenatally diagnosed cases. Of these, 67% were associated with additional cardiac malformations, whereas only two involved extracardiac anomalies, and none were linked to chromosomal abnormalities. The increasing number of reported cases in recent years likely reflects advancements in prenatal ultrasound technology. Nevertheless, APW remains a rare condition, and clinical experience with its prenatal diagnosis is still limited. Importantly, no correlation was found between isolated APW and microduplication 22q11 or any other chromosomal disorder, suggesting that further genetic investigations may not be required when antenatal ultrasound confirms an isolated defect.

TABLE 1.

Antenatal diagnosis of aortopulmonary window (review of literature 2017–2025).

Case	References	Maternal age	Gestational age	Aortopulmonary window	Cardiac abnormality	Extracardiac abnormality	Chromosome abnormality
1	Tongprasert et al. Case 1 [14]	29	19	Type I	Left superior vena cava	Hydrocephalus	46XY del 22q11 not done
2	Tongprasert et al. Case 2 [14]	31	20	Type I	Abnormal course of the pulmonary artery	None	46XY del 22q11 not done
3	Tongprasert et al. Case 3 [14]	25	21	Type I	Abnormal course of the pulmonary artery	None	46XY No del 22q11
4	Li et al. 2018 Case 1 [15]	31	27	Type II	Interrupted aortic arch type A; Right pulmonary artery originated from the aorta	None	46XY del 22q11 not done
5	Li et al. 2018 Case 2 [15]	29	27	Type II	None	None	46XY del 22q11 not done
6	Li et al. 2018 Case 3 [15]	41	25	Type II	Right aortic arch	None	46XY del 22q11 not done
7	Li et al. 2018 Case 4 [15]	26	27	Type II	None	None	46XY del 22q11 not done
8	Li et al. 2018 Case 5 [15]	32	26	Type II	Interrupted aortic arch type A; Right pulmonary artery originated from the aorta	None	46XY del 22q11 not done
9	Li et al. 2018 Case 6 [15]	28	25	Type III	None	None	46XY del 22q11 not done
10	Li et al. 2018 Case 7 [15]	27	29	Type II	Right aortic arch	None	46XY del 22q11 not done
11	Li et al. 2018 Case 8 [15]	30	30	Type II	None	None	46XY del 22q11 not done
12	Babaoğlu et al. [16]	28	22	Type I	None	None	46XY No del 22q11
13	Louis‐Jacques et al. [17]	26	30	Type III	Aberrant right subclavian artery	None	NA
14	Kaya et al. Case 1 [18]	23	24	Type I	None	None	No del 22q11
15	Kaya et al. Case 2 [18]	26	25	Type I	Hypoplastic left heart	None	NA
16	Bernal Quintero et al. [19]	25	22	Not disclosed	Double aortic arch	None	46XY
17	Tang et al. Case 1 [20]	24–33	26	Type I	Ventricular septal defect	None	46XY
18	Tang et al. Case 2 [20]		25	Type II	Ventricular septal defect, Interrupted aortic arch	None	NA
19	Tang et al. Case 3 [20]		26	Type II	Dandy–Walker Syndrome	None	46XY
20	Tang et al. Case 4 [20]		27	Type I	Ventricular septal defect	None	NA
21	Tang et al. Case 5 [20]		26	Type II	Atrioventricular defect	None	46XY
22	Tang et al. Case 6 [20]		24	Type II	None	None	46XY
23	Tang et al. Case 7 [20]		25	Type I	None	None	46XY
24	Tang et al. Case 8 [20]		28	Type II	None	None	NA
25	Tang et al. Case 9 [20]		27	Type II	Ventricular septal defect	None	NA
26	Tang et al. Case 10 [20]		24	Type I	None	None	NA
27	Yu et al. [21] Case 1	24 + 2	27.9 ± 4.3	Type I	TOF + pulmonary atresia	None	NA
28	Yu et al. [21] Case 2	28 + 3		Type I	None	None	NA
29	Yu et al. [21] Case 3	19 + 5		Type I	Single atrium, single ventricle, aortic valve atresia	None	NA
30	Yu et al. [21] Case 4	24 + 0		Type I	Permanent upper left cavity	None	NA
31	Yu et al. [21] Case 5	25 + 3		Type II	Berry syndrome	None	NA
32	Yu et al. [21] Case 6	24 + 5		Type II	Berry syndrome	None	NA
33	Yu et al. [21] Case 7	26 + 5		Type II	None	None	NA
34	Yu et al. [21] Case 8	35 + 0		Type III	Ventricular septal defect, right aortic arch	Hydrocephalus	NA
35	Hejazi et al. [22]	22	20	Type II	Bicuspid aortic valve ASD	None	46XX
36	Sylwestrzak et al. [23]	34	30	NA	ASD + ARCAPA	None	NA
37	Li et al. 2024 [24]	23	30	NA	Berry syndrome	None	NA

Abbreviations: ARCAPA, anomalous right coronary artery from the pulmonary artery; ASD, atrial septal defects; NA, not available; TOF, Tetralogy of Fallot.

Further research and case studies are needed to improve prenatal diagnosis of this rare condition. Given the potential severity of APW, early recognition is critical to guide delivery planning, surgical intervention, and long‐term follow‐ups.

Author Contributions

Clara Cao: conceptualization, writing – original draft. Aurélie D'Hondt: validation, writing – review and editing. Hughes Dessy: writing – review and editing. Catherine Donner: project administration, writing – original draft, writing – review and editing.

Disclosure

The authors have nothing to report.

Consent

Written informed consent was obtained from the mother for the use of clinical data and the publication of this case report. A copy of the signed consent form is available and retained by the authors.

Cao C., D'Hondt A., Dessy H., and Donner C., “Prenatal Diagnosis of Aortopulmonary Window in a Twin Pregnancy: Case Report and Review of the Literature,” Clinical Case Reports 13, no. 9 (2025): e70884, 10.1002/ccr3.70884.

Data Availability Statement

Data sharing not applicable to this article as no datasets were generated or analyzed during the current study.