Intermittent Constriction of the Ductus Arteriosus in the Fetus: A Cause for Concern?

In November 1999, a 35-year-old woman was referred for a routine screening fetal echocardiogram at 23 weeks' gestation because she had previously given birth to a child with congenital heart disease. The current pregnancy was uncomplicated. A level I ultrasound examination at 20 weeks' gestation had been normal. The mother had not been ill, nor had she ingested any medications during her pregnancy.

The initial fetal echocardiogram at 23 weeks demonstrated constriction of the ductus arteriosus, with a 20–25 mmHg ductal gradient from the pulmonary artery to the descending aorta (Fig. 1). The remainder of the fetal echocardiogram was normal: there was no evidence of ventricular dysfunction, valvular regurgitation, or hydrops fetalis. Repeat fetal echocardiography at 26 weeks' gestation revealed normal ductal patency. Color-flow and pulse-wave Doppler examinations were normal (Fig. 2). Another echocardiographic examination at 29 weeks' gestation was also normal; however, at 33 weeks the ductus was again noted to be constricted at its distal insertion into the descending aorta.

Fig. 1 A) Fetal 2-D echocardiogram in the short-axis view at 23 weeks' gestation reveals the constricted ductus arteriosus. B) Color-flow Doppler echocardiogram in the short-axis view demonstrates flow acceleration in the ductus arteriosus. C) Pulse-wave Doppler in the ductus arteriosus shows a velocity of 2.3 m/s (21 mmHg gradient).

Fig. 2 A) Color-flow Doppler echocardiogram at 26 weeks' gestation shows normal flow through the fetal ductus arteriosus. B) Pulse-wave Doppler shows normal flow velocities (<1 m/s) in the ductus arteriosus.

Intrauterine growth retardation was noted at 37 weeks' gestation. Amniocentesis revealed a mature fetus, and elective induction of labor was performed. Delivery of the infant was uneventful, and Apgar scores were normal (9 at 1 and 5 minutes). The placenta was also examined and found to be normal. Except for small size (birth weight, 2.4 kg), the newborn physical examination was completely normal. Echocardiography was performed immediately after delivery. This study revealed constriction of the ductus arteriosus at the distal insertion into the descending aorta, similar to that noted on the fetal echocardiograms at 23 and 33 weeks (Fig. 3). The remainder of the ductus arteriosus was widely patent. A mild to moderate degree of left-to-right shunting was present at the ductal level. The remainder of the neonatal echocardiogram was normal for age.

Fig. 3 A) Neonatal 2-D echocardiogram in the short-axis view reveals the constricted ductus arteriosus. B) Color-flow Doppler demonstrates constriction of the ductus at its point of insertion into the descending aorta.

This case demonstrates that intermittent constriction of the ductus arteriosus can occur in the absence of identifiable causes. In these cases, the fetus may be at risk for intrauterine complications, including growth retardation, cardiac compromise, and hydrops fetalis. Careful echocardiographic follow-up throughout gestation seems warranted.