CHALLENGING CASES: BIOPSYCHOSOCIAL PEDIATRICS Failure to Thrive in a 4-Month-Old Nursing Infant*

CASE Christine, a 4-month-old infant, is brought to the office for a health-supervision visit by her mother, a 30-year-old emergency department nurse. The mother, who is well known to the pediatrician to be a competent and attentive caregiver, appears uncharacteristically tired. They are accompanied by the 18month-old and 4-year-old siblings because child care was unavailable, and her husband has been out of town on business for the last 5 weeks. When the pediatrician comments, “You look exhausted. It must be really tough to care for 3 young children,” the mother appears relieved that attention was given to her needs. She reports that she has not been getting much sleep because Christine wakes up for 2 or more evening feedings and the toddler is now awakening at night. During the day, she juggles nursing the baby, caring for her other 2 young children, and managing the household. Although visibly fatigued and mildly depressed, the mother appears comfortable holding Christine; the baby likewise appeared closely attached. The mother has no concerns regarding Christine’s health or development. During the physical examination, Christine is a slightly thin but active and alert infant. She has no remarkable or focal physical findings; her muscle strength, tone, and reflexes are normal. She achieves all motor, social, and language milestones for a 4-month-old infant. Plotting her height and weight on the growth chart, the pediatrician and mother were surprised to see that her weight did not change in 2 months, and her linear growth decelerated slightly. The growth measurements were repeated and corroborated. In the office, Christine was a vigorous feeder, latching onto the full areola quickly. During the nursing session, she studies her mother’s face, cooed, and reached out for the breast with her free hand. The mother reports that breastfeeding occurs every 4 to 5 hours for at least 10 minutes on each breast. Her urine output and bowel movements are normal, and she did not have a history of vomiting or excessive regurgitation. The mother’s diet and fluid intake seem adequate. A review of past medical history does not reveal an explanation for Christine’s failure to gain weight. She was born full-term after an uncomplicated pregnancy and a normal spontaneous vaginal delivery. Her birth weight was 8 pounds. She was nursing vigorously by the time of discharge from the hospital. At her 2-week and 2-month health-supervision visits, her weight and linear growth and developmental milestones were normal. In addition, at those visits she was observed to respond quickly to visual and auditory cues. There was no family history of serious diseases. In that a comprehensive history and physical examination did not indicate an organic cause, the pediatrician reasoned that the most likely cause of her failure to thrive was an unintentional caloric deprivation secondary to maternal stress and exhaustion. Christine’s mother and the pediatrician discussed how maternal stress, fatigue, and depression could hinder the let-down reflex and reduce the availability of an adequate milk supply, as well as make it difficult to maintain regular feeding sessions. The pediatrician recommended obtaining help with child care and household responsibilities. The mother was also encouraged to consume adequate fluids, eat high-protein foods, nurse more frequently, and offer a formula supplement after nursing 3 times a day. At the same time that these therapeutic interventions were initiated, screening laboratory studies were obtained. All results were normal, including a complete blood cell count with differential; serum electrolytes, creatinine, hepatic transaminase (ATL), total protein, and albumin; urinalysis; and stool fat stain and occult blood. A serum thyroxine was normal (6.3 mg/dL). A plan was made for Christine to return to the office in 1 week.