My baby was born 4 weeks early and had a meconium plug that didn't pass till hour 57. Cystic fibrosis has been ruled out. What are the chances it's hirschsprungs? Or could it just be chance?

Likely it's chance. CF is one of the causes of meconium plug, but mostly it's a random happenstance. Ruling out CF is important. As long as your child is starting to have normal stools now, and they are fairly regular, it's very unlikely it's hirschsprungs. Generally anal stenosis, hirschsprungs, or other forms of obstruction would cause chronic constipation. If your child is stooling normally, i'd go with it.
Still small. Is the baby a boy? Chance is 1/5000 but about 1/1000 for boys. Having a late first bm is a sign but in a premature baby everything is off. If the baby's belly is soft and bowl movements are now regular then not to worry. Make sure you voice your concern to the pediatrician.
Hirschsprung Dis:(H) Due to absence of ganglion cells in lower bowel wall, extending from anus up. Seen in full term (less in preterm), m:f = 4:1, increase familial incidence, may be associated with other anomalies. 99% full term infant passes meconeum in 48 hrs of birth, h pts. Passes late, becomes chronically constipated. Check bowel movement. If chr. Constipation talk to pcp. Tests: rectal manometry/ suction biopsy.
Mecon. plug syndrome. Meconium plug syndrome has been described in infants born premature or of diabetic mothers. Essentially there is immaturity of ganglion cells in large bowel. This is a transient problem that does usually not cause difficulties later on in life. Initially child needs stimulation to bowel, enema etc, to move the plug out of bowel.Radiographic enema sometimes shows characteristic pattern.

Related Questions

Is meconium plug syndrome only associated with cystic fibrosis?

Not only, but often. No. Certainly patients with meconium plug have a higher risk of CF and must be tested, many babies with this do not have cf. Hirschsprung's disease should also be tested for. Read more...
No. Meconium plug syndrome can occur as an isolated event. It can also be associated with other genetic conditions such as hirschsprung disease. Read more...
No. Meconium plug syndrome, as opposed to meconium ileus, is not necessarily associated with cf. It can occur with hirschsprung's disease. It is usually self-limited, however, and clears with a contrast enema undertaken to establish the diagnosis. If the baby stools normally after initial evacuation, additional work-up is usually not necessary. Read more...
No. It can be associated with maternal diabetes, small left colon syndrome, hirschsprung's disease, or electrolyte imbalances in the infant. Read more...