ABO incompatibility: A condition that may lead to neonatal hemolytic disease. The pregnant woman has
group O red blood cells and antibodies to group A and B red blood cells. These antibodies are trans-
ferred to the fetus and cause destruction of fetal red blood cells. While this process is similar to Rh in-
compatibility, the hemolytic disease resulting from ABO incompatibility is less severe than the disease
caused by Rh incompatibility. Unlike Rh incompatibility, ABO incompatibility cannot be prevented by
giving the mother Rh immune globulin.
Acidosis: Abnormally low pH of the blood. The range of blood pH in a healthy neonate is between 7.25
and 7.35. A blood pH of 7.20 or lower is considered severe acidosis. Acidosis may result from metabolic
disturbances in which the serum bicarbonate is low or inadequate respiratory efforts in which serum car-
bon dioxide is high. Often metabolic and respiratory factors simultaneously influence the blood pH. Aci-
dotic babies are usually lethargic and may have mottled or grayish colored skin. If extremely acidotic,
babies typically take deep, regular gasping breaths. If a baby is gasping, the pH is probably 7.00 or less.
Acidosis should be corrected promptly, most commonly with assisted ventilation when due to inadequate
respiratory effort or occasionally by administration of sodium bicarbonate if due to metabolic factors.
Acoustic stimulation: A test in which fetal response to a sound when produced by a device placed
against the maternal abdomen and triggered to give a loud, 1-second buzz is used as an estimate of fetal
well-being. This test may be used during a nonstress test or labor.
Adrenaline: Ofﬁcial British Pharmacopoeia name for epinephrine. The trademark name for epinephrine
preparations is Adrenalin.
AGA: See Appropriate for gestational age.
Age, adjusted: See Age, corrected.
Age, chronologic: Number of days, weeks, months, or years that have elapsed since birth.
Age, conceptional: Time elapsed between the day of conception and day of delivery. Note: The term
conceptual age is incorrect and should not be used. Conceptional age may be used when conception
occurred as a result of assisted reproductive technology, but should not be used to indicate the age of a
fetus or newborn. See also Age, gestational.
Age, corrected: Chronologic age in weeks or months reduced by the number of weeks born before
40 weeks of gestation. It is used only for children up to 3 years of age who were born preterm. It is the
preferred term to use after neonatal hospitalization, and should be used instead of adjusted age. Exam-
ple: A 24-month-old child born at 28 weeks’ gestation has a corrected age of 21 months.
Age, gestational: Number of completed weeks between the ﬁrst day of the woman’s last menstrual period
and the day of delivery (or the date of an assessment is performed if the woman has not yet delivered). If
pregnancy was achieved using assisted reproductive technology and, therefore, the date of fertilization or
implantation is deﬁned, gestational age may be calculated by adding 2 weeks to the conceptional age.
Age, postmenstrual: Weeks of gestational age plus chronologic age. It is the preferred term to describe
the age of preterm infants during neonatal hospitalization. Note: Postconceptional age should not be
used. Example: A baby born at 331/7 weeks with a chronologic age of 54/7 weeks has a postmenstrual
age of 385/7 weeks.
AIDS: Symptomatic stage of the illness caused by HIV.
Albumin: The major protein in blood.
Alkalosis: Abnormally high pH of the blood. Range of blood pH in a healthy neonate is between 7.25
and 7.35. Alkalosis may result from a high serum bicarbonate or, more commonly, when the carbon di-
oxide concentration in a baby’s blood is lowered by hyperventilation (assisting the baby’s breathing at an
excessively fast rate). Babies who are alkalotic may not respond to stimulation intended to increase their
breathing efforts until their blood carbon dioxide level rises toward the reference range.