This disorder may result from postmaturity, diabetes in the mother, twin-to-twin transfusions, in which blood flows from one fetus to the other, or a low oxygen level in the fetus's blood.
A high concentration of red blood cells makes the blood thick (hyperviscosity) and may slow blood flow through small blood vessels.
Most affected newborns do not have symptoms but occasionally have a ruddy or dusky color, are sluggish (lethargic), feed poorly, and very rarely have seizures.
The diagnosis is based on a test that measures the amount of red blood cells in the blood.
Usually no treatment is needed except to give fluids.
When the newborn has symptoms, treatment with a partial exchange transfusion may be given to reduce the concentration of red blood cells.
Red blood cells contain hemoglobin, a protein that gives blood its red color and enables it to carry oxygen from the lungs and deliver it to all body tissues. Oxygen is used by cells to produce energy that the body needs, leaving carbon dioxide as a waste product. Red blood cells carry carbon dioxide away from the tissues and back to the lungs.
A markedly increased concentration of red blood cells may cause the blood to be too thick. Blood that is too thick slows the flow of blood through small blood vessels and interferes with the delivery of oxygen to tissues. A newborn who is born postterm Postterm Newborns A postterm newborn is a baby delivered after 42 weeks of gestation. Near the end of a term pregnancy, the function of the placenta decreases, providing fewer nutrients and less oxygen to the... read more or whose mother has diabetes Diabetes During Pregnancy For women who have diabetes before they become pregnant, the risks of complications during pregnancy depend on how long diabetes has been present and whether complications of diabetes, such... read more , has severe high blood pressure High Blood Pressure During Pregnancy High blood pressure (hypertension) during pregnancy is classified as one of the following: Chronic hypertension: Blood pressure was high before the pregnancy. Gestational hypertension: Blood... read more , smokes, or lives at a high altitude is more likely to have polycythemia.
Polycythemia may also result if the newborn receives too much blood from the placenta (the organ that connects the fetus to the uterus and provides nourishment to the fetus) at birth, which may occur if the newborn is held below the level of the placenta for too long before the umbilical cord is clamped.
Other causes of polycythemia include a low oxygen level in the blood (hypoxia), perinatal asphyxia Perinatal asphyxia Birth injury is damage that occurs as a result of physical pressure during the birthing process, usually during transit through the birth canal. Many newborns have minor injuries during birth... read more 
, growth restriction in the womb, birth defects Overview of Birth Defects Birth defects, also called congenital anomalies, are physical abnormalities that occur before a baby is born. They are usually obvious within the first year of life. The cause of many birth... read more (such as some heart problems Overview of Heart Defects About one in 100 babies is born with a heart defect. Some are severe, but many are not. Defects may involve abnormal formation of the heart's walls or valves or of the blood vessels that enter... read more or kidney problems Kidney Defects There are several different birth defects that affect the kidneys (the two organs that filter waste from the blood to make urine). These defects are not usually apparent at the doctor's examination... read more ), Down syndrome Down Syndrome (Trisomy 21) Down syndrome is a chromosome disorder caused by an extra chromosome 21 that results in intellectual disability and physical abnormalities. Down syndrome is caused by an extra chromosome 21... read more 
, Beckwith-Wiedemann syndrome, or a large transfusion of blood from one twin to another (twin-to-twin transfusion).
Symptoms of Polycythemia in the Newborn
A newborn with severe polycythemia has a very ruddy or dusky color, is lethargic, feeds poorly, and may have seizures Seizures in Children Seizures are a periodic disturbance of the brain’s electrical activity, resulting in some degree of temporary brain dysfunction. When older infants or young children have seizures, they often... read more .
Diagnosis of Polycythemia in the Newborn
Blood test
To diagnose polycythemia, the newborn gets a blood test. If the results of the blood test indicate the newborn has too many red blood cells, the newborn may be treated for polycythemia.
Treatment of Polycythemia in the Newborn
Fluids by vein
Sometimes partial exchange transfusion
If the newborn has no symptoms, fluids for hydration are given by vein because dehydration Dehydration in Children Dehydration is loss of water from the body, usually caused by vomiting and/or diarrhea. Dehydration occurs when there is significant loss of body water and, to varying amounts, electrolytes... read more (fluid loss) can make the blood even thicker.
If the newborn has symptoms, some of the newborn’s blood is removed and replaced with an equal amount of salt water (saline) solution. This procedure, called partial exchange transfusion, dilutes the remaining red blood cells and corrects the polycythemia.
