The neonatal heart is a remarkable and rapidly developing organ. It assumes a central role immediately after birth, adapting to life outside the womb. This tiny, yet powerful, pump undergoes significant changes to support the newborn’s independent existence. Its proper function is important for the baby’s overall health and development.
The Transformative Shift in Circulation
The journey from fetal to postnatal circulation involves a physiological transformation of the heart and blood vessels. Inside the womb, the fetus receives oxygen and nutrients directly from the mother through the placenta via the umbilical cord. Because the lungs are not used for breathing before birth, the fetal circulatory system includes specialized shunts that divert blood away from them.
One shunt is the foramen ovale, an opening between the right and left atria. This allows oxygenated blood from the placenta to bypass the lungs and flow directly into the left atrium and to the rest of the body. Another shunt, the ductus arteriosus, connects the pulmonary artery to the aorta, diverting blood away from the lungs. These shunts ensure blood bypasses the fluid-filled, non-functional lungs.
At birth, the umbilical cord is clamped. With the newborn’s first breaths, the lungs expand and fluid clears, decreasing pulmonary pressure. This causes the foramen ovale to close, usually within days or weeks, as blood flow to the lungs increases. The ductus arteriosus also constricts and closes, often within days, due to increased oxygen and prostaglandin changes. These closures reroute blood flow to the now-functional lungs for oxygenation.
Common Heart Conditions in Newborns
Despite the circulatory system’s transition, some newborns experience heart conditions. Congenital heart defects (CHDs) are structural problems affecting approximately 1 in 100 babies. These defects can involve the heart’s walls, valves, or major blood vessels. For example, septal defects, or “holes in the heart,” are openings in the walls separating the heart’s chambers, allowing oxygen-rich and oxygen-poor blood to mix.
Two conditions that may persist are patent ductus arteriosus (PDA) and patent foramen ovale (PFO). A patent ductus arteriosus occurs when this vessel remains open after birth. This can lead to excess blood flow to the lungs, causing breathing difficulties and increased heart workload. While small PDAs may close on their own, larger ones might require intervention.
A patent foramen ovale is when the foramen ovale does not fully seal after birth. This condition is common in newborns and often benign, usually causing no symptoms. In some cases, a PFO may even be beneficial by allowing blood to mix and reduce symptom severity. However, if a PFO persists and is associated with other health issues, its significance can be evaluated.
Monitoring and Recognizing Signs
Medical professionals monitor a newborn’s heart health. A physical examination is performed within 24 hours of birth, assessing heart rate, rhythm, and murmurs. The normal newborn heart rate ranges from 120 to 160 beats per minute. Femoral pulses are also checked and compared to brachial pulses to detect conditions like coarctation of the aorta.
Newborn screenings aid in early detection. Pulse oximetry screening, performed when a baby is at least 24 hours old, measures oxygen levels in the blood using sensors on the hand and foot. Low oxygen levels or a significant difference in readings can indicate a congenital heart defect or other issues. If a baby does not pass this screening, further evaluation, such as an echocardiogram (an ultrasound of the heart), may be recommended.
Parents should be aware of signs that might indicate a heart concern in their newborn. These include:
A bluish tint to the skin, lips, or nail beds (cyanosis).
Rapid or difficult breathing.
Excessive sweating during feeding.
Poor feeding leading to inadequate weight gain.
Swelling in the legs, abdomen, or around the eyes.
Decreased alertness or unusual tiredness.
Promptly communicate any of these observations with a healthcare provider for timely diagnosis and management.