Cystic fibrosis (CF) is a life-shortening disease that causes breathing and digestive problems, but can now be diagnosed at the time of birth. Lung function is very hard to measure in infants, but growth is not. In this study the investigators aim to define growth in infants with CF in the first year of life with research quality precision and to understand factors that interfere with good growth.

Pancreatic enzyme replacement therapy (PERT) will be also be studied in a subgroup of infants. Two different doses of PERT will be evaluated for improving fat and nitrogen absorption in infants with CF.

Newborn screening (NBS) for cystic fibrosis (CF) has decreased the prevalence of malnutrition in infancy, but suboptimal nutrition still persists. In one study, 60% of infants diagnosed by NBS achieved their birth weight percentile by two years of age, while 40% did not. The many factors that contribute to this poor growth have not been defined and persist despite pancreatic enzyme supplementation. Although published guidelines for the clinical management of infants with cystic fibrosis in the U.S. and Europe exist, there is an alarming scarcity of evidence to dictate care. In order to proceed with large scale randomized studies to evaluate the range of interventions for infants with CF, we need to not only develop precise techniques for measuring growth but also pursue unexplored factors that may contribute to poor growth.

This is a multi-center observational clinical study with a nested interventional PERT sub-study. The observational study was designed to follow in a prospective manner incident cases of CF for up to 12 months. The PERT sub-study is a randomized, double-blind, crossover sub-study designed to evaluate the efficacy and safety of two doses of PERT (pancreatic enzyme replacement therapy) for improving coefficient of fat absorption (CFA) in the stool of infants with CF. The PERT sub-study was unable to enroll and closed. No results available.

Observational Study

Inclusion Criteria:

1. Signed informed consent

2. Males or females no more than three and one half (3.5) months of age at enrollment

3. Documentation of a CF diagnosis as evidenced by:

   1. One or more of the following: one or more clinical features consistent with the CF phenotype OR a positive newborn screening (NBS) OR a positive pre-natal screen

      AND

   2. One or more of the following: sweat chloride ≥ 60 mEq/liter by quantitative pilocarpine iontophoresis test (QPIT) OR two well-characterized mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene

4. Enrolled in the Cystic Fibrosis Foundation Patient Registry. (Patients may enroll in the Registry at Enrollment Visit if not previously enrolled.)

Exclusion Criteria:

1. Children unable to take full oral feeds
2. Any serious or active medical condition, which in the opinion of the investigator, contributes to malabsorption, interferes with normal growth, or would otherwise interfere with subject's treatment, assessment, or compliance with the protocol.
3. Gestational age less than 35 weeks and/or birth weight < 2.5 kg.

Infants diagnosed with CF who attend regular clinic visits during the first year of life