20.4 Birth Weight

Small for Gestational Age

Small for gestational age (SGA) refers to newborns who have a birth weight and size that is below the 10th percentile for their gestational age. Some infants are small because their parents are small in stature, but most babies who are SGA have a condition called intrauterine growth restriction (IUGR). IUGR happens when the fetus doesn’t receive enough nutrients and oxygen during pregnancy, impacting the growth and development of their organs and tissues. IUGR can be caused by many factors^[1]:

• Maternal factors: Maternal factors related to IUGR include high blood pressure, diabetes, chronic kidney disease, heart disease, respiratory disease, malnutrition or anemia, infection, alcohol or drug use, and cigarette smoking.
• Placental or pregnancy factors: Placental factors include decreased blood flow in the uterus and placenta, placenta previa, and placental abruption. Pregnancy factors include multiple gestation (i.e., twins, triplets, or more) or infection, such as chorioamnionitis.
• Fetal factors: Chromosome problems or congenital birth defects

SGA may be diagnosed during pregnancy based on maternal weight gain and fundal measurements during prenatal care visits, or information from ultrasound results. Although SGA infants may be physically mature on delivery, they may be weak, hypothermic, hypoglycemic, and less able to feed. Treatment of a SGA newborn includes thermoregulation with an infant warmer or incubator, tube feedings if the infant does not have a strong suck or has poor intake, blood glucose monitoring and treatment of hypoglycemia, and oxygen therapy.^[2]

Nursing care for SGA newborns is focused on supporting their growth, development, and overall well-being as they transition to life outside the uterus and includes the following components:

• Assessments: Nurses closely monitor temperature, heart rate, respiratory rate and oxygen saturation levels, and assess the infant’s weight, length, and head circumference to track growth and development. The newborn’s feedings and intake are closely monitored because SGA infants may have a weak suck or difficulty breastfeeding.
• Support Feeding and Nutritional Intake: Collaborate with a lactation consultant to facilitate breastfeeding. SGA infants often need extra support and techniques to latch and feed effectively. Teach parents about positioning during feedings and frequency of feedings, as well as monitoring the number of wet diapers and stools daily to determine intake. If breastfeeding is not insufficient, if the mother prefers bottle feeding, or if tube feeding is ordered, prepare and administer formula per provider orders.
• Regulate Temperature: Keep the infant’s environment warm and ensure they are dressed in appropriate clothing to maintain body temperature. Use infant warmers or incubators as needed to prevent hypothermia.
• Provide Respiratory Care: Monitor the infant’s respiratory status closely, as SGA infants are at higher risk of respiratory distress syndrome (RDS) and persistent pulmonary hypertension of the newborn (PPHN). Administer oxygen therapy and respiratory support as prescribed.
• Monitor Blood Glucose: SGA infants are at an increased risk of hypoglycemia and require glucose monitoring. Administer glucose supplements or intravenous glucose as indicated to maintain stable blood glucose levels.
• Provide Developmental Care: Encourage skin-to-skin contact to promote bonding, regulate body temperature, and enhance the newborn’s overall well-being.
• Prevent Infection: Implement strict infection control practices to reduce the risk of infections for SGA infants that can lead to sepsis.
• Provide Health Teaching and Support: Educate parents about the infant’s condition, their care needs, signs of potential complications, and when to promptly notify the provider. Offer emotional support and encourage them to ask questions and verbalize their feelings.
• Collaborate with the Health Care Team: Collaborate with neonatologists, pediatricians, and other health care professionals to ensure a comprehensive care plan for the infant. Communicate effectively with the interdisciplinary team to promptly address potential complications.

Large for Gestational Age

Large for gestational age (LGA) refers to newborns who are in the 90th percentile or higher for their weight compared to other infants of the same age. A newborn who weighs more than 8 pounds, 13 ounces (4,000 grams), regardless of their gestational age, is diagnosed with macrosomia. Although most LGA infants are born at term (37 to 41 weeks of pregnancy), premature babies may also be LGA. Some infants are large because their parents have a large stature, and excessive weight gain during pregnancy can also cause LGA. However, the most common cause of LGA is maternal diabetes during pregnancy that causes elevated blood glucose levels, resulting in excessive fetal growth and fat deposits.^[3]

Fetal complications related to LGA during delivery include fetal distress related to prolonged labor, vaginal birth injuries (such as fractured clavicle or brachial plexus injury), shoulder dystocia, and increased incidence of cesarean delivery. Fetal complications after delivery include hypoglycemia, respiratory distress syndrome, and hyperbilirubinemia.^[4]

LGA may be diagnosed during pregnancy based on maternal weight gain and fundal measurements during prenatal care visits or based on ultrasound results. A planned cesarean delivery may be recommended depending on the ultrasound estimate of the baby’s weight. After delivery, a LGA infant is carefully examined for birth injuries, and routine blood glucose testing is performed to monitor for hypoglycemia. Respiratory status and bilirubin levels are also closely monitored.