Circulatory changes following intrauterine closure of the ductus arteriosus in the human fetus and newborn

Ductus Arteriosus in Fetal and Perinatal Life

The ductus arteriosus represents an essential vascular structure connecting the pulmonary artery and the aorta. Over the past decades, there has been substantial advancement in our understanding of both the fundamental and clinical aspects of the ductus arteriosus. In particular, the clarification of the regulatory mechanisms governing ductal patency in critical stages such as the fetal and the perinatal period has enabled optimal management of both physiological and pathological conditions in which the ductus arteriosus plays a crucial role. Furthermore, a more in-depth understanding of the regulatory mechanisms controlling this fundamental structure has facilitated the development of advanced therapeutic strategies and personalized interventions. In the present review, we provide a comprehensive overview of the ductus arteriosus during fetal and perinatal life, encompassing its physiological functions, pathological conditions, and clinical implications. Through this examination, we aim to contribute to a broader understanding of the ductus arteriosus' role in these critical developmental stages and its significance in clinical practice.

Cardiovascular fetal-to-neonatal transition: an in silico model

BACKGROUND

Previous models describing the fetal-to-neonatal transition often lack oxygen saturation levels, homeostatic control mechanisms, phasic hemodynamic signals, or describe the heart with a time-varying elastance model.

METHODS

We incorporated these elements in the adapted CircAdapt model with the one-fiber model for myocardial contraction, to simulate the hemodynamics of the healthy term human fetal circulation and its transition during the first 24 h after birth. The fetal-to-neonatal model was controlled by a time- and event-based script of changes occurring at birth, such as lung aeration and umbilical cord clamping. Model parameters were based on and validated with human and animal data.

RESULTS

The fetal circulation showed low pulmonary blood flow, right ventricular dominance, and inverted mitral and tricuspid flow velocity patterns, as well as high mean ductus venosus flow velocity. The neonatal circulation showed oxygen saturation levels to gradually increase to 98% in the first 15 min after birth as well as temporary left ventricular volume overload.

CONCLUSIONS

Hemodynamics of the term fetus and 24-h-old neonate, as well as the events occurring directly after birth and the transition during the first 24 h after birth, were realistically represented, allowing the model to be used for educational purposes and future research.

IMPACT

With the addition of oxygen saturation levels, homeostatic pressure-flow control mechanisms, and the one-fiber model for myocardial contraction, a new closed-loop cardiovascular model was constructed to give more insight into the healthy term human fetal circulation and its cardiovascular transition during the first 24 h after birth. Extensive validation confirmed that the hemodynamics of the term fetus and the fetal-to-neonatal transition were realistically represented with the model. This well-validated and versatile model can serve as an education as well as a research platform for in silico investigation of fetal-to-neonatal hemodynamic changes under a wide range of physiological and pathophysiological conditions.

Isolated Dissection of the Ductus Arteriosus Associated with Sudden Unexpected Intrauterine Death

We report five cases of sudden intrauterine death due to premature closure of the ductus arteriosus. In four cases, this was caused by dissecting the hematoma of the ductus arteriosus with intimal flap and obliteration of the lumen. In one case, the ductus arteriosus was aneurysmatic, with lumen occlusion caused by thrombus stratification. No drug therapy or free medication consumption were reported during pregnancy. The time of stillbirth ranged between 26 and 33 gestational weeks. We performed TUNEL analysis for apoptosis quantification. The dissecting features were intimal tears with flap formation in four of the cases, just above the origin of the ductus arteriosus from the pulmonary artery. The dissecting hematoma of the ductus arteriosus extended downward to the descending aorta and backward to the aortic arch with involvement of the left carotid and left subclavian arteries. TUNEL analysis showed a high number of apoptotic smooth muscle cells in the media in two cases. Abnormal ductal remodeling with absence of subintimal cushions, lacunar spaces rich in glycosaminoglycans (cystic medial necrosis), and smooth muscle cell apoptosis were the pathological substrates accounting for failure of remodeling process and dissection.

Dysfunction of the foetal arterial duct results in a wide spectrum of cardiovascular pathology

OBJECTIVE

Foetal ductal problems may have various cardiopulmonary consequences. This study aimed to identify the spectrum of ductus arteriosus (DA) dysfunction (closure, constriction, kinking, aneurysm and thrombosis) and the resultant clinical and echocardiographic presentation in foetuses and neonates.

METHODS AND RESULTS

This is a retrospective analysis of serial pre- and post-natal data of 27 cases of foetal ductal dysfunction diagnosed at a median gestational age of 33 weeks (range 20-39). The most common abnormalities observed were premature closure of the DA in 56% (15/27) and constriction in 29% (8/27). Right ventricular hypertrophy was present in 75% (n = 11/15) of foetuses with premature DA closure, while ventricular dilation (4/7, 57%) was a more common feature in foetuses with ductal constriction. After birth, 63% (17/27) of new borns presented with cyanosis and pulmonary hypertension that required active treatment. Three infants died after birth. Abnormalities resolved spontaneously after birth in about 50% of patients. In some children, pulmonary valve stenosis and regurgitation was progressive and required further treatment.

CONCLUSIONS

An abnormal right heart on foetal four-chamber ultrasound view should alert the sonographer to the possible presence of foetal ductal dysfunction. Ductal occlusion, transient or fixed constriction, kinking and aneurysm formation are associated with foetal cardiopulmonary sequelae. Symptoms and pathology is probably related to the type, foetal age, rapidity of progression and duration of intrauterine ductal dysfunction. Correspondingly, clinical outcomes vary ranging from little or no symptoms to severe respiratory distress and even foetal or neonatal death.

Bronchopulmonary dysplasia: A review of pathogenesis and pathophysiology

Bronchopulmonary dysplasia (BPD) is a chronic lung disease of primarily premature infants that results from an imbalance between lung injury and repair in the developing lung. BPD is the most common respiratory morbidity in preterm infants, which affects nearly 10, 000 neonates each year in the United States. Over the last two decades, the incidence of BPD has largely been unchanged; however, the pathophysiology has changed with the substantial improvement in the respiratory management of extremely low birth weight (ELBW) infants. Here we have attempted to comprehensively review and summarize the current literature on the pathogenesis and pathophysiology of BPD. Our goal is to provide insight to help further progress in preventing and managing severe BPD in the ELBW infants.

Prognostic factors of premature closure of the ductus arteriosus in utero: a systematic literature review

BACKGROUND

A number of case reports show various outcomes of premature closure of the ductus arteriosus in utero, including persistent pulmonary hypertension of the newborn and fetal or neonatal death; however, no study clarifies the clinical observations that are related to their prognoses. We aimed to clarify the prognostic factors of intrauterine ductal closure by a systematic literature review. Data sources We searched PubMed database (1975-2014) to identify case reports and studies on intrauterine closure of the ductus arteriosus, including maternal, fetal, and neonatal clinical information and their prognoses.

RESULTS

We analysed the data of 116 patients from 39 articles. Of these, 12 (10.3%) died after birth or in utero. Fetal or neonatal death was significantly correlated with fetal hydrops (odds ratio=39.6, 95% confidence interval=4.6-47.8) and complete closure of the ductus arteriosus (odds ratio=5.5, 95% confidence interval=1.2-15.1). Persistent pulmonary hypertension was observed in 33 cases (28.4%), and was also correlated with fetal hydrops (odds ratio=4.2, 95% confidence interval=1.3-4.6) and complete closure of the ductus arteriosus (odds ratio=5.5, 95% confidence interval=1.6-6.0). Interestingly, maternal drug administration was not correlated with the risk of death and persistent pulmonary hypertension.

CONCLUSIONS

Fetal hydrops and complete ductal closure are significant risk factors for both death and persistent pulmonary hypertension. Cardiac or neurological prognoses could be favourable if the patients overcome right heart failure during the perinatal period.

Selective serotonin reuptake inhibitor exposure constricts the mouse ductus arteriosus in utero

Use of selective serotonin reuptake inhibitors (SSRIs) is common during pregnancy. Fetal exposure to SSRIs is associated with persistent pulmonary hypertension of the newborn (PPHN); however, a direct link between the two has yet to be established. Conversely, it is well known that PPHN can be caused by premature constriction of the ductus arteriosus (DA), a fetal vessel connecting the pulmonary and systemic circulations. We hypothesized that SSRIs could induce in utero DA constriction. Using isolated vessels and whole-animal models, we sought to determine the effects of two commonly prescribed SSRIs, fluoxetine and sertraline, on the fetal mouse DA. Cannulated vessel myography studies demonstrated that SSRIs caused concentration-dependent DA constriction and made vessels less sensitive to prostaglandin-induced dilation. Moreover, in vivo studies showed that SSRI-exposed mice had inappropriate DA constriction in utero. Taken together, these findings establish that SSRIs promote fetal DA constriction and provide a potential mechanism by which SSRIs could contribute to PPHN.

Diagnosis and management of fetal ductus arteriosus constriction-closure

Pathognomonic features of in utero premature restriction/closure of the ductus arteriosus (DA) are increased right ventricular afterload, impaired right ventricular function, and consequently tricuspid regurgitation and right heart dilation. The most common reason for constriction-closure of DA is maternal administration of non-steroidal anti-inflammatory drugs (NSAIDs) during the 3rd trimester of gestation. The idiopathic form is a rare event and, maybe, an underestimated abnormality that, if it is not promptly recognized, may result in severe fetal-neonatal compromise. We describe a case of a 38-year-old woman presenting at 34+0 weeks of gestation with a normally grown male fetus whose fetal echocardiography had shown right ventricular hypertrophy, a tortuous S-shaped DA and a significant pulmonary hyperflow. All signs were consistent of an idiopathic severe constriction of DA with a significant fetal cardiac involvement. The patient was admitted to a tertiary care center equipped with Neonatal Intensive Care Unit (NICU), and delivered by cesarean section at 34+4 weeks with a good maternal and neonatal outcome. Based on our experience and a review of the Literature we propose a management algorithm to use when dealing with preterm or early term pregnancy complicated by this fetal hemodynamic malfunction.

Prenatal sonographic diagnosis of premature constriction of the fetal ductus arteriosus after maternal self-medication with benzydamine hydrochloride: report of 3 cases and review of the literature

We report 3 cases of prenatal diagnosis of premature constriction of the ductus arteriosus after maternal benzydamine hydrochloride therapy (3-mg lozenges) in third-trimester pregnancies. In each case, fetal echocardiography revealed a dilated, hypocontractile right ventricle with severe tricuspid regurgitation and constriction of the ductus arteriosus. Although the effect of indomethacin and other nonsteroidal anti-inflammatory drugs on prenatal ductal constriction is well known, readily available over-the-counter nonsteroidal anti-inflammatory drugs such as benzydamine can have an equally deleterious effect and are best avoided in the third trimester of pregnancy.

Dextro-transposition of the great arteries in a neonate with ventricular septal defect and pulmonary stenosis complicated by premature closure of the ductus arteriosus and possible pathophysiology of both defects

Premature closure of the ductus arteriosus (PCDA) and transposition of the great arteries (TGA) cause persistent pulmonary hypertension of the newborn (PPHN). We present a case of a newborn who demonstrated d-TGA with ventricular septal defect (VSD) and pulmonary stenosis (PS) complicated by PCDA. The neonate showed severe cyanosis resistant to resuscitation soon after birth, and was diagnosed with d-TGA with VSD by echocardiography. PPHN was also suspected based on physical symptoms and results of echocardiography. The neonate was given inhaled nitric oxide, prostaglandin E1, and catecholamines under sedation, and underwent a balloon atrial septostomy (BAS). His condition gradually improved, and he was extubated on day 7, but his pulmonary subvalvular stenosis gradually worsened and pulmonary blood flow was markedly decreased. A second BAS was performed on day 27 and he showed no improvement. Blalock-Taussig shunt surgery was performed on day 34, which markedly improved his condition. The co-existence of d-TGA and PCDA is generally a lethal state. In our patient, an increase in pulmonary blood flow during the fetal period was restricted because of PS and outlet flow from the left ventricle to the right ventricle via the VSD. This restricted blood flow through the ductus arteriosus, which led to narrowing of the DA. At the same time, damage to and constrictive changes of the pulmonary vessels were prevented. The ductus arteriosus should be carefully evaluated to exclude PCDA in cases of d-TGA. The presence of both VSD and PS may be a prognostic factor in such cases.

A case of progressive ductal constriction in a fetus

The ductus arteriosus is a normal and essential structure in fetal circulation. Since the introduction of fetal echocardiography, there have been reports of ductal constriction, many of which were related to maternal use of some medications. However, there have been some reports of idiopathic ductal constriction, which usually present in later gestation. Recently we experienced a case, which initially showed an S-shaped ductus with mild narrowing at 23 weeks and 27 weeks gestation and developed severe ductal constriction at 33 weeks. Soon after birth, ductus was searched for but no ductus was found in 2-D and color images. The neonate required mechanical ventilation with supplemental oxygen for 3 days. All echocardiographic abnormalities were normalized in 7 months. We report progressive ductal constriction in an S-shaped ductus and emphasize the importance of continuous follow up extending to the third trimester and even immediately after birth.

Tricuspid atresia with progressive ductal restriction in a fetus

We report a unique case of tricuspid and pulmonary atresia with idiopathic progressive ductus arteriosus restriction in utero. Diligent predelivery planning and a controlled delivery environment led to a favorable outcome.

Idiopathic constriction of the fetal ductus arteriosus: three cases and review of the literature

Premature constriction or closure of the ductus arteriosus can occur during fetal life. It is a rare phenomenon and has been described secondary to medication or structural lesions or as idiopathic constriction. Premature closure of the ductus arteriosus can lead to progressive right heart dysfunction with tricuspid regurgitation, congestive heart failure, fetal hydrops, and intrauterine death. This series describes diagnosis of fetal ductus arteriosus constriction of unknown etiology in 3 cases, prenatal management, and outcomes. Constriction of the ductus arteriosus can be diagnosed prenatally with careful interrogation of the ductal arch using pulsed Doppler sonography and complete fetal echocardiography. Close monitoring is mandatory to rule out development of right heart failure and to determine the intervention time.

Enhanced central and conduit pulmonary arterial reservoir function offsets reduced ductal systolic outflow during constriction of the fetal ductus arteriosus

Constriction of the fetal ductus arteriosus (DA) has disparate effects on mean and phasic hemodynamics, as mean DA blood flow is preserved until constriction is severe, but DA systolic and diastolic blood velocities change with only mild constriction. To determine the basis of this disparity and its physiological significance, seven anesthetized late-gestation fetal sheep were instrumented with pulmonary trunk (PT), DA, and left pulmonary artery (PA) micromanometer catheters and transit-time flow probes. Blood flow profile and wave intensity analyses were performed at baseline and during mild, moderate, and severe DA constriction (defined as pulmonary-aortic mean pressure differences of 4, 8, and 14 mmHg, respectively), produced with an adjustable snare. With DA constriction, mean DA flow was initially maintained but decreased with severe constriction (P < 0.05) in conjunction with a reduction (P < 0.05) in PT flow (i.e., right ventricular output). By contrast, DA systolic flow fell progressively during DA constriction (P < 0.001), due to decreased transmission of both early and midsystolic proximal flow-enhancing forward-running compression waves into the DA. However, DA constriction was also accompanied by greater systolic storage of blood in the PT and main PA (P < 0.025), and increased retrograde diastolic flow from compliant major branch PA (P < 0.001). Transductal discharge of these central and conduit PA blood reservoirs in diastole offset systolic DA flow reductions. These data suggest that, during DA constriction in the fetus, enhanced central and conduit PA reservoir function constitutes an important compensatory mechanism that contributes to preservation of mean DA flow via a systolic-to-diastolic redistribution of phasic DA flow.

Clinical features of the complete closure of the ductus arteriosus prenatally

OBJECTIVE

Prenatal constriction of the ductus arteriosus associated with maternal drug ingestion was reported several decades ago. There are fewer reports of the complete closure of the ductus arteriosus; therefore, the clinical features of the latter are poorly understood. The aim of this study is to clarify the clinical features of complete ductal closure and postnatal pulmonary hypertension by performing echocardiography of the fetus.

PATIENTS

We diagnosed four fetuses with complete ductal closure by performing fetal echocardiography and reviewed the prenatal and postnatal medical records of the mother and fetus.

RESULTS

One mother each had bronchial asthma, ulcerative colitis, and idiopathic thrombocytopenic purpura, and they had received nonsteroidal anti-inflammatory drugs and/or corticosteroids during pregnancy. The fourth mother did not have basal disease and had not ingested any drugs. Fetal diagnosis was performed at 32-38 weeks of gestation. All fetuses had right heart dilatation with tricuspid regurgitation in the absence of any cardiac defects, and Doppler echocardiography indicated that the right ventricular pressure was elevated. Two of the fetuses had fetal hydrops, which suggested severe right heart dysfunction. All fetuses were delivered by emergent cesarean delivery. After birth, all the infants developed persistent pulmonary hypertension and required oxygen inhalation. Of these, three required mechanical ventilation, and two, nitric oxide inhalation. All infants improved within 2 weeks, and they had no neurological and cardiac complications after discharge.

CONCLUSION

Right heart dilatation and severe tricuspid regurgitation in the absence of a cardiac defect in the fetus strongly suggested ductal dysfunction. Careful evaluation of ductal patency and right ventricular function can lead to precise early diagnosis and good prognosis.

Idiopathic severe constriction of the fetal ductus arteriosus: a possible underestimated pathophysiology

Idiopathic intrauterine constriction/closure of the ductus arteriosus, which is distinct from that secondary to maternal exposure to non-steroidal anti-inflammatory drugs, such as indomethacin, or structural cardiac defect, is an uncommon event that often results in severe fetal-neonatal morbidity and mortality. We reported a case of idiopathic fetal ductal constriction, in which the diagnosis was confirmed by documentation of an abnormal four-chamber view of the fetal heart at 38 weeks of gestation on obstetric ultrasound examination. A female infant weighing 2,816 g was born by Cesarean section, and her postnatal course was mild; transient tachypnea requiring only several days of supplemental oxygen with spontaneous regression of the abnormal echocardiographic findings by 3 months of age. The incidence of idiopathic constriction/closure of the fetal ductus arteriosus may be underestimated, particularly with a negative history of maternal drug exposure and mild postnatal clinical presentation.

Fermeture anténatale du canal artériel chez un fœtus suite à une intoxication maternelle par acide niflumique

Antenatal closure of the ductus arteriosus is an uncommon event that has been considered as a risk factor for development of congestive heart failure and persistent pulmonary hypertension of the newborn. We report here on a case of antenatal ductus arteriosus closure due to niflumic acid maternal intoxication at 32 weeks of gestation. Fetal extraction was performed few days later because of echographic signs of congestive heart failure. The child survived after 3 days of severe persistent pulmonary hypertension. This case emphasizes the potential risk of niflumic acid during pregnancy and the need of antenatal echographic monitoring for optimal management.

Severe ductal constriction in the third-trimester fetus following maternal self-medication with nimesulide

OBJECTIVE

This was a multicenter series of 10 cases of constriction of the fetal ductus arteriosus occurring after maternal ingestion of one or two oral doses of nimesulide, which led to emergency delivery in four cases.

METHODS

The computerized databases of three referral centers were searched for all cases of ductal constriction detected during the last 8 years in association with maternal ingestion of nimesulide. Ten cases were retrieved and represent the study population. The following variables were analyzed: gestational age at diagnosis, reason for nimesulide ingestion, total nimesulide dose, time interval between drug intake and ultrasound examination, indication for echocardiography, presence of right ventricular hypertrophy, presence of tricuspid valve regurgitation, ductal systolic and diastolic peak velocities, ductal pulsatility index, signs of fetal heart failure, pregnancy and feto-neonatal outcome, and ductal status at neonatal echocardiography.

RESULTS

Nimesulide ingestion was the result of self-medication in all cases. The mean gestational age at diagnosis was 36.3 weeks and the mean time interval between nimesulide intake and echocardiographic examination was 2.9 days. The five cases with ductal peak velocities > 2.5 m/s showed right ventricular dysfunction with significant tricuspid regurgitation. At echocardiography performed immediately after birth, the ductus appeared closed in all cases and two neonates showed persistent pulmonary hypertension requiring intermittent positive pressure ventilation and nitric oxide therapy for 1 week.

CONCLUSIONS

Although the true incidence of the adverse effect of nimesulide ingestion during pregnancy cannot be deduced, we believe that patients and their clinicians should be alerted to the possibility that clinically significant ductal constriction may follow maternal self-medication with just one or two oral doses of nimesulide, at least if the drug is taken near term.

Double-chamber right ventricle associated with severe fetal cardiac failure

Fetal cardiac defects leading to intrauterine cardiac failure and subsequent fetal hydrops are rare. We report an unusual case of a double-chamber right ventricle leading to progressive fetal cardiac insufficiency and hydrops. The patient was first managed conservatively. Delivery by Cesarean section was performed for a pathological fetal heart-rate tracing at 28 weeks of gestation. The newborn died 4 h postpartum due to generalized cardiac insufficiency.

Coexistence of ductal constriction and closure of the foramen ovale in utero

We report a fetus with an unusual combination of a narrow ductus arteriosus (DA) and foramen ovale. A pregnant mother was referred at 26 weeks of gestation for fetal pericardial effusion. Fetal echocardiography showed pericardial effusion, right atrial enlargement, right ventricular hypertrophy, and tricuspid regurgitation. The DA looked tortuous with S-shaped kinking. The atrial septum primum bulged into the left atrium. Color Doppler did not show any flow across the atrial septum. Cesarean section was performed at 31 weeks of gestation. Admission to intensive care was required after delivery, but the infant gradually improved and was discharged home without any sequela.

Interventional treatment for fetus and newborn infant with congenital heart disease

BACKGROUND

Catheter intervention has become popular not only in adult patients but in younger patients with congenital heart disease. The early neonatal catheter interventional treatment has also been attempted in conjunction with the development of prenatal diagnosis of the congenital heart disease.

METHOD

Recent articles concerning several severe structural cardiac diseases in newborns, such as critical aortic stenosis, complete transposition of the great arteries, premature constriction of the ductus arteriosus, and pulmonary stenosis or atresia with intact ventricular septum are introduced with consideration.

RESULTS

This study investigated our own experiences of early neonatal balloon valvuloplasty in a patient with critical aortic stenosis carried out immediately after the delivery following prenatal diagnosis. A case with prenatal diagnosis of premature constriction of ductus arteriosus which could prevent persistent pulmonary hypertension of the newborn by early delivery at 39 weeks and 1 day of gestation were reported.

CONCLUSION

Several cardiac interventional treatments performed in the present time during the perinatal period and some prospects in the near future are described in the discussion.

Cardiac output and central distribution of blood flow in the human fetus

BACKGROUND

The objectives of this study were to establish reference ranges for left and right cardiac output and to investigate blood flow distribution through the foramen ovale, ductus arteriosus, and pulmonary bed in human fetuses.

METHODS AND RESULTS

A prospective study was performed in 222 normal fetuses from 13 to 41 weeks of gestation with high-resolution color Doppler ultrasound. Cardiac output and ductal flow were calculated by use of vessel diameter and the time-velocity integral. Pulmonary blood flow was expressed as the difference between right cardiac output and ductal flow. Foramen ovale flow was estimated as the difference between pulmonary flow and left cardiac output. Gestational age-specific reference ranges are given for left, right, and biventricular output and volume of ductal blood flow, showing an exponential increase with gestational age. Median ratio of right to left cardiac output was 1.42 and was not associated with gestational age. Right cardiac output was 59% and left cardiac output was 41% of biventricular cardiac output. Median biventricular cardiac output was estimated to be 425 mL. min(-1). kg(-1) fetal weight. Ductal blood flow was 46%, estimated pulmonary flow was 11%, and estimated foramen ovale flow was 33% of biventricular output.

CONCLUSIONS

The study establishes reference ranges for fetal cardiac output and offers insights into the central blood flow distribution in human fetuses from 13 weeks to term. There is a clear right heart dominance. The estimated ratio of pulmonary blood flow to cardiac output is higher than in fetal lamb studies.

Reference ranges for two-dimensional echocardiographic examination of the fetal ductus arteriosus

OBJECTIVES

To establish reference ranges for 2D-echocardiographic examination of the fetal ductus arteriosus and its relationship to the main pulmonary artery and the aorta.

METHODS

A prospective cross-sectional echocardiographic study was performed in 222 normal fetuses from 13 to 41 weeks of gestation using high resolution/color Doppler ultrasound equipment.

RESULTS

Gestational age-specific reference ranges are given for the diameter of the pulmonary valve anulus, diameter of the ductus arteriosus at its beginning, middle, and end, ductal length, ductal diameter-to-pulmonary valve anulus diameter ratio, and the spatial relationship of the ductus arteriosus to the main pulmonary artery and to the aorta.

CONCLUSIONS

The presented data derived from a study group of 222 normal fetuses provide in-vivo insights into the morphology of the ductus arteriosus and its relationship to the adjacent vessels. The reference ranges may be helpful in prenatal diagnosis of cardiac malformations and abnormalities of the ductus arteriosus, such as obstruction or aneurysm from 13 to 41 weeks of gestation.

Blood flow velocity waveforms of the fetal pulmonary artery and the ductus arteriosus: reference ranges from 13 weeks to term

OBJECTIVE

To establish reference ranges for blood flow velocity waveforms of the fetal main pulmonary artery and the ductus arteriosus during the second and third trimesters of pregnancy.

METHODS

A prospective cross-sectional echocardiographic study was performed in 222 normal fetuses from 13 to 41 weeks of gestation using high resolution/color Doppler ultrasound equipment.

RESULTS

Gestational age-specific reference ranges are given for peak velocity across the pulmonary valve, velocities in the ductus arteriosus, peak systolic velocity in the ductus arteriosus-to-peak velocity across the pulmonary valve ratio, ductal systolic velocity-to-diastolic velocity ratio, ductal resistance index and ductal pulsatility index. In the ductus arteriosus, increasing fetal heart rate was significantly associated with increasing end-diastolic velocity and decreasing systolic-to-diastolic ratio, decreasing resistance index, and decreasing pulsatility index.

CONCLUSIONS

Based on a prospective study in more than 200 normal fetuses, the data provide gestational age specific reference ranges for blood flow velocity waveforms of the fetal pulmonary artery and the ductus arteriosus. The reference ranges may be helpful in prenatal diagnosis of cardiac malformations and ductal obstruction from 13 to 41 weeks of gestation.