Hannah, a 1-year-old girl, is brought to the clinic for a routine immunization by her mother. Mr. and Mrs. Rosen have a healthy 5-year-old boy at home. The pregnancy with Hannah was uneventful and a fetal ultrasound done at 16 weeks gestation was normal. The baby was born by spontaneous vaginal delivery, breathed immediately, and was placed on the breast for mom to nurse. Hannah's birth weight was 3.4 Kg. After seeming to feed normally for 24 hours, Hannah vomited bile and the abdomen was noted to be distended. An x-ray was interpreted as showing a distal small bowel obstruction. Further contrast x-rays of the colon showed a microcolon and inspissated meconium in the proximal colon, making a diagnosis of meconium ileus. Genetic testing confirmed cystic fibrosis.