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You are seeing a 4 week old brought in for vomiting with every feed. The vomitus is non-bilious, non-projectile, and non-bloody. The baby is making 5 wet diapers per day and weighs 10 lbs, and has gained 30 gm per day since regaining birth weight at 10 days of age. The baby is formula feeding, taking 5 ounces every 2-3 hours.

Which is atypical for a 4 week old?