European Journal of Cardiovascular Medicine

Congenital Heart Diseases (CHD’s) are among the most common structural anomalies detected prenatally, with an incidence of approximately 8-10 per 1000 live births. Fetal aortic stenosis (AS), a form of left ventricular outflow tract obstruction, represents about 3-6 % of all CHDs.^[1] Early prenatal diagnosis through anomaly scan and fetal echocardiography has improved understanding and management of these complex lesions. Maternal hypothyroidism can lead to fetal cardiac remodelling and functional alterations such as changes in ventricular wall thickness and cardiac output. There is evidence that children born to hypothyroid mothers may face risks such as low birth weight and neurodevelopmental delays.^[2] Direct literature evidence of fetal aortic stenosis with maternal gestational hypothyroidism is sparse. We report a case of a 33-year-old primigravida diagnosed antenatally with gestational hypothyroidism and fetal aortic stenosis, successfully managed through elective lower segment caesarean section (LSCS), followed by neonatal intensive care support. The case underscores the importance of multidisciplinary management in optimizing both maternal and fetal outcomes in the presence of congenital cardiac anomalies.

A 33-year-old Primigravida was admitted at 37 weeks of gestation with complaints of decreased fetal movements for one day. There was no significant medical or surgical history apart from hypothyroidism diagnosed in early pregnancy, for which she was on treatment with Levothyroxine 50 mcg. She had no known allergy and her previous menstrual cycles were regular with a flow of 4-5 days. She was on regular antenatal checkups. Her level 1 anomaly scan and Double marker test were done at 12 weeks and were reported as normal. She was referred to our Centre at 22 weeks when her Level II Anomaly scan showed mild cardiomegaly with dilated LVOT and a small subaortic VSD. Further evaluation with fetal echocardiography was carried out, which showed mild aortic stenosis with biventricular hypertrophy and LV Z score of 0.60, which was within normal limits. Hence, she was advised to continue her pregnancy. The rest of her antenatal period was uneventful, and repeat fetal echocardiography at 34 weeks revealed progression of biventricular hypertrophy(Figure 1) with dilation of the RA and RV with mild flow acceleration in the LV mid cavity and valve level (Figure 2) with V max across the aortic valve 112 cm/sec, suggesting possible aortic stenosis. With these findings there was also evidence of right ventricular dysfunction; hence severity of LVOT obstruction was difficult to quantify (Figure 3),considering this the patient was counselled for elective LSCS at 37 weeks. High risks and need for neonatal intervention were explained to parents.

She was scheduled for elective LSCS at 37 weeks of gestation. On admission, her vitals were stable, with term term-sized uterus with no contractions. FHR was regular, and she was not in labour. Her USG on admission showed a term active fetus. She was given 2 doses of Betnesol and prepared for elective LSCS after 2 days. She underwent elective LSCS under spinal anaesthesia. A 2.7Kg Male baby was delivered by LSCS with an APGAR of 4/10. The baby was pale with a weak cry and a pulse rate of less than 100 beats per minute. The neonate was resuscitated and shifted to the NICU. Echocardiography of the neonate showed subvalvular mild aortic stenosis with biventricular hypertrophy with RV dysfunction. There was no coarctation of the aorta but there was mild pulmonary hypertension. The baby was managed with Injection furosemide and high-flow nasal oxygen. The baby was on conservative management for 7days and no immediate surgical intervention was necessary. Oxygen was weaned off and furosemide was continued orally and oral propanalol was added considering hypertrophied ventricles. The baby was shifted with the mother once there was no signs of distress and the baby was sucking well. The condition of both the mother and the baby were stable and they were discharged on day 10.

Aortic stenosis in the fetus is relatively rare, occurring in less than 10% of new borns,^[1] most often caused by valvular dysplasia or narrowing of the left ventricular outflow tract. Congenital aortic stenosis originates from improper development of the aortic valve during the first 8 weeks of fetal life. The valve leaflets may be thickened, fused, or hypoplastic, resulting in restricted valve opening. The stenosis causes increased afterload on the left ventricle, which leads to compensatory left ventricular hypertrophy initially, and if severe or untreated, progressive left ventricular dilation and dysfunction occurs. Critical stenosis may lead to endocardial fibroelastosis (EFE), a thickening of the endocardium due to fibrosis, further impairing ventricular compliance. Reduced forward flow across the aortic valve increases left ventricular pressure, reduces stroke volume, and increases left atrial pressure. The left ventricular end-diastolic volume can fall over time, contributing to evolving hypoplastic left heart syndrome (HLHS) if untreated.^[3]

It is typically diagnosed between 18 to 24 weeks gestation. Detection is essential for timely counseling, planning delivery at tertiary centers, and potential fetal interventions. Clinical manifestations in utero are usually identified by abnormalities in fetal echocardiography. Severe cases may progress to hydrops fetalis due to congestive heart failure, evident by fetal edema and effusions.^[4]

Prenatal diagnosis is typically achieved during the mid -trimester anomaly scan or through targeted fetal echocardiography. Doppler evaluation assesses valve gradients and flow patterns across the left heart, although quantification of stenosis severity can be challenging due to altered ventricular function and fetal shunts like the ductus arteriosus. Serial echocardiography is necessary for monitoring progression, as severity of the obstruction and ventricular dysfunction may worsen as pregnancy advances.^[5]

Mild to moderate stenosis can be managed conservatively while severe cases can occasionally benefit from in utero intervention such as fetal aortic valvuloplasty, though access remains limited in many regions. Fetal aortic valvuloplasty (FV) is offered in the setting of significant aortic stenosis, with the intent to alter fetal left heart hemodynamics that might result in univentricular (UV) circulation after birth. However, the procedure is not without risk and experienced centers report a 10% procedure-related loss.^[6,7] with higher losses reported by multicenter registries with more varied experience.^[8]

Several studies^[9,10] have emphasized that the prognosis largely depends on the degree of obstruction, ventricular function, and associated anomalies such as ventricular septal defect (VSD) .Postnatal management involves careful haemodynamic stabilization , diuretic therapy and surgical correction if indicated.

Our case, characterized by mild subvalvular aortic stenosis, adds to existing evidence supporting conservative postnatal management in hemodynamically stable neonates. This case highlights the value of antenatal detection and multidisciplinary coordination among obstetricians, fetal medicine specialists, neonatologists and paediatric cardiologists. The presence of mild to moderate obstruction allowed favorable neonatal adaptation.

Previous literature suggests that fetuses with mild or moderate AS often survive the perinatal period without the need for emergency cardiac surgery. Continuous follow-up is crucial as progressive obstruction or ventricular dysfunction can occur postnatally. With improvements in fetal imaging, more of these patients are identified and they have variable outcomes. Approximately one third of these patients underwent aortic valve intervention by one year of life.^[11] Survival rates for critical AS diagnosed prenatally have improved due to better prenatal assessment and neonatal care. Nevertheless, morbidity remains significant, especially when HLHS develops. The goal of postnatal care is to ensure adequate cardiac output and prevent heart failure while planning definitive repair or palliation.^[12]

Continued advancements in fetal cardiac interventions and improved prenatal diagnostics hold promise for better long-term outcomes for affected foetuses. Hereby we report a mild foetal AS, wherein timely diagnosis, planned delivery, and coordinated neonatal care contributed to a positive outcome. Continuous follow-up is crucial, as progressive obstruction or ventricular dysfunction can occur postnatally.

Early recognition of fetal cardiac anomalies through targeted ultrasound and echocardiography enables optimal planning of delivery and neonatal management. In mild forms of Aortic Stenosis with stable hemodynamics, conservative neonatal care can yield favorable outcomes. Regular follow-up remains essential to monitor potential progression.

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