In utero, the ductus arteriosus (DA) serves to divert ventricular output away from the lungs and toward the placenta by connecting the main pulmonary artery to the descending aorta. A patent ductus arteriosus (PDA) in the first 3 days of life is a physiologic shunt in healthy term and preterm newborn infants, and normally is substantially closed within about 24 hours after bith and completely closed after about three weeks. Failure of physiologcal closure is referred to a persistent or patent ductus arteriosus (PDA). Depending on the degree of left-to-right shunting, PDA can have clinical consequences.

Failure of the foramen ovale to seal postnatally, leaving a potential conduit between the left and right cardiac atria.

Difficulty in swallowing.

Absence of neurologic reflexes such as the knee-jerk reaction.

A delay in the achievement of motor or mental milestones in the domains of development of a child, including motor skills, speech and language, cognitive skills, and social and emotional skills. This term should only be used to describe children younger than five years of age.

An abnormality characterized by disruption of the normal functioning of peripheral axons.

A reduction in the number of axons in the peripheral nervous system.

An abnormality of the gyri (i.e., the ridges) of the cerebral cortex of the brain.

Spinal muscular atrophy (SMA) is characterized by muscle weakness and atrophy resulting from progressive degeneration and irreversible loss of the anterior horn cells in the spinal cord (i.e., lower motor neurons) and the brain stem nuclei. The onset of weakness ranges from before birth to adulthood. The weakness is symmetric, proximal > distal, and progressive. Before the genetic basis of SMA was understood, it was classified into clinical subtypes based on maximum motor function achieved; however, it is now apparent that the phenotype of SMN1-associated SMA spans a continuum without clear delineation of subtypes. With supportive care only, poor weight gain with growth failure, restrictive lung disease, scoliosis, and joint contractures are common complications; however, newly available targeted treatment options are changing the natural history of this disease.

Reduced strength of muscles.

A flexion contracture is a bent (flexed) joint that cannot be straightened actively or passively. It is thus a chronic loss of joint motion due to structural changes in muscle, tendons, ligaments, or skin that prevents normal movement of joints.

The presence of skeletal muscular atrophy (which is also known as amyotrophy).

A severe degree of muscular hypotonia characterized by markedly reduced muscle tone.

An abnormally high degree of muscle fiber size variation. This phenotypic feature can be observed upon muscle biopsy.

The presence of bone fractures in the prenatal period that are diagnosed at birth or before.

Generalized muscular hypotonia (abnormally low muscle tone).

Multiple congenital contractures in different body areas.

A congenital abnormality in which the lung parenchyma is not fully developed. It may be associated with other congenital abnormalities.

A severe form of respiratory insufficiency characterized by inadequate gas exchange such that the levels of oxygen or carbon dioxide cannot be maintained within normal limits.

Respiratory difficulty as newborn.

The presence of excess amniotic fluid in the uterus during pregnancy.

The birth of a baby of less than 37 weeks of gestational age.

An abnormal reduction in quantity or strength of fetal movements.