EVALUATION OF THE NEWBORN INFANT
Saturday, August 16, 2008
HISTORY
Taking the history in newborn medicine involves three key areas: (1) the medical history of the mother and father, including a relevant genetic history; (2) the history pertaining to the mother’s previous pregnancies; and (3) the history of the current pregnancy, including antepartum and intrapartum events.
The mother’s medical history should include any chronic medical conditions, medications taken during pregnancy, unusual dietary habits, smoking history, occupational exposures to chemicals or infections of potential risk to the fetus, and pertinent aspects of the social history that may suggest increased risks for parenting problems and child abuse. Family illnesses with genetic implications should be sought. The past pregnancy history should include maternal age, gravidity and parity, blood type, and pregnancy outcomes. The current obstetric history should include documentation and results of procedures such as ultrasound, amniocentesis, screening tests (eg, HBsAg, antibody screen, serum AFP, HIV), and antepartum tests of fetal well-being (eg, biophysical profiles or nonstress tests). Information should be sought regarding pregnancy-related illnesses in the mother such as urinary tract infection, pregnancy-induced hypertension or preeclampsia-eclampsia, vaginal bleeding, and preterm labor. Peripartum events of importance include duration of ruptured membranes, maternal fever, fetal distress or meconium-stained amniotic fluid, type of delivery (vaginal or cesarean section), anesthesia and analgesia used, reason for operative or forceps delivery, and condition of the infant at birth, including any resuscitation needed and Apgar scores.
ASSESSMENT OF GROWTH & GESTATIONAL AGE
It is important to know an infant’s gestational age because its behavior and anticipated problems can be predicted on this basis. Accurate recall of the date of the last menstrual period is the best indicator of gestational age. Other obstetric observations, such as fundal height, time of auscultation of fetal heartbeat with a stethoscope, and early ultrasound examination, provide supporting information. A postnatal examination can also be used because fetal physical characteristics and neurologic development progress in predictable fashion. Table 1–2 lists the physical and neurologic criteria to be examined. The upper panel is the neuromuscular examination, assessing primarily muscle tone and strength. The lower panel catalogs a variety of physical characteristics. Adding the scores assigned to each characteristic yields a total score that corresponds to the gestational age.
Disappearance of the anterior vascular capsule of the lens is also helpful in determining gestational age. At 27–28 weeks’ gestation, the lens capsule is covered by vessels; by 34 weeks, this vascular plexus is completely atrophied. Foot length, measured carefully from the heel to the tip of the longest toe, also correlates with gestational age in appropriately grown infants. The foot measures 4.5 cm at 25 weeks’ gestation and increases by 0.25 cm/wk until term.
By convention, unless the physical examination indicates a gestational age more than 2 weeks different (in either direction) from the obstetric dates, the gestational age is as assigned by the dates. The birth weight and gestational age must be plotted on an appropriate standard to determine if the infant’s weight is appropriate for gestational age (AGA), small for gestational age (SGA) or intrauterine growth restricted (IUGR), or large for gestational age (LGA) (Figure 1–1). Birth weight and gestational age distributions vary from one population to the next depending on factors such as those listed in Table 1–3. Whenever possible, standards should be prepared from data derived from the local population, but when such information is not available any regional standard may be used. The birth weight–gestational age distribution of an infant is a screening tool that should be supplemented by clinical data confirming a tentative diagnosis of intrauterine growth restriction or excessive fetal growth. These data include not only the clinical features of the infant determined during the physical examination but also factors such as the size of the parents and the birth weight–gestational age distribution of infants previously born to the parents.
The fact that SGA infants have fewer problems (such as respiratory distress syndrome) than AGA infants of the same birth weight but a lower gestational age has led to the common misconception that SGA infants have accelerated maturation. SGA infants, when compared to AGA infants of the same gestational age, actually have increased morbidity and mortality rates.
Knowledge of a baby’s birth weight in relation to gestational age is also helpful in anticipating neonatal problems. LGA babies are at risk for birth trauma, hypoglycemia, polycythemia, congenital anomalies, cardiomyopathy, hyperbilirubinemia, and hypocalcemia. SGA babies are at risk for fetal distress during labor and delivery, polycythemia, hypoglycemia, and hypocalcemia.
Taking the history in newborn medicine involves three key areas: (1) the medical history of the mother and father, including a relevant genetic history; (2) the history pertaining to the mother’s previous pregnancies; and (3) the history of the current pregnancy, including antepartum and intrapartum events.
The mother’s medical history should include any chronic medical conditions, medications taken during pregnancy, unusual dietary habits, smoking history, occupational exposures to chemicals or infections of potential risk to the fetus, and pertinent aspects of the social history that may suggest increased risks for parenting problems and child abuse. Family illnesses with genetic implications should be sought. The past pregnancy history should include maternal age, gravidity and parity, blood type, and pregnancy outcomes. The current obstetric history should include documentation and results of procedures such as ultrasound, amniocentesis, screening tests (eg, HBsAg, antibody screen, serum AFP, HIV), and antepartum tests of fetal well-being (eg, biophysical profiles or nonstress tests). Information should be sought regarding pregnancy-related illnesses in the mother such as urinary tract infection, pregnancy-induced hypertension or preeclampsia-eclampsia, vaginal bleeding, and preterm labor. Peripartum events of importance include duration of ruptured membranes, maternal fever, fetal distress or meconium-stained amniotic fluid, type of delivery (vaginal or cesarean section), anesthesia and analgesia used, reason for operative or forceps delivery, and condition of the infant at birth, including any resuscitation needed and Apgar scores.
ASSESSMENT OF GROWTH & GESTATIONAL AGE
It is important to know an infant’s gestational age because its behavior and anticipated problems can be predicted on this basis. Accurate recall of the date of the last menstrual period is the best indicator of gestational age. Other obstetric observations, such as fundal height, time of auscultation of fetal heartbeat with a stethoscope, and early ultrasound examination, provide supporting information. A postnatal examination can also be used because fetal physical characteristics and neurologic development progress in predictable fashion. Table 1–2 lists the physical and neurologic criteria to be examined. The upper panel is the neuromuscular examination, assessing primarily muscle tone and strength. The lower panel catalogs a variety of physical characteristics. Adding the scores assigned to each characteristic yields a total score that corresponds to the gestational age.
Disappearance of the anterior vascular capsule of the lens is also helpful in determining gestational age. At 27–28 weeks’ gestation, the lens capsule is covered by vessels; by 34 weeks, this vascular plexus is completely atrophied. Foot length, measured carefully from the heel to the tip of the longest toe, also correlates with gestational age in appropriately grown infants. The foot measures 4.5 cm at 25 weeks’ gestation and increases by 0.25 cm/wk until term.
By convention, unless the physical examination indicates a gestational age more than 2 weeks different (in either direction) from the obstetric dates, the gestational age is as assigned by the dates. The birth weight and gestational age must be plotted on an appropriate standard to determine if the infant’s weight is appropriate for gestational age (AGA), small for gestational age (SGA) or intrauterine growth restricted (IUGR), or large for gestational age (LGA) (Figure 1–1). Birth weight and gestational age distributions vary from one population to the next depending on factors such as those listed in Table 1–3. Whenever possible, standards should be prepared from data derived from the local population, but when such information is not available any regional standard may be used. The birth weight–gestational age distribution of an infant is a screening tool that should be supplemented by clinical data confirming a tentative diagnosis of intrauterine growth restriction or excessive fetal growth. These data include not only the clinical features of the infant determined during the physical examination but also factors such as the size of the parents and the birth weight–gestational age distribution of infants previously born to the parents.
The fact that SGA infants have fewer problems (such as respiratory distress syndrome) than AGA infants of the same birth weight but a lower gestational age has led to the common misconception that SGA infants have accelerated maturation. SGA infants, when compared to AGA infants of the same gestational age, actually have increased morbidity and mortality rates.
Knowledge of a baby’s birth weight in relation to gestational age is also helpful in anticipating neonatal problems. LGA babies are at risk for birth trauma, hypoglycemia, polycythemia, congenital anomalies, cardiomyopathy, hyperbilirubinemia, and hypocalcemia. SGA babies are at risk for fetal distress during labor and delivery, polycythemia, hypoglycemia, and hypocalcemia.
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