Breast milk is the reference normative standard for infant feeding. When an infant is diagnosed with chylothorax, provision of breast milk must be temporarily discontinued due to the presence of long chain triglycerides (LCT) that contribute to persistent chylous drainage. In its place, the infant is prescribed a therapeutic formula high in medium chain triglycerides (MCT) as treatment for chylothorax. Families and health care providers are interested in using breast milk, in a modified fat form, as treatment for chylothorax instead. This study will assess growth in infants receiving one of two nutrient enriched modified fat breast milk (MFBM) treatments for chylothorax. If either of the proposed nutrient enrichment methods support growth, MFBM will become a standard chylothorax treatment option for infants at SickKids.

Inclusion Criteria:

• confirmed diagnosis of chylothorax following cardiothoracic surgery
• previously receiving a minimum of 50% of feeds from breast milk 3 days prior to surgical procedure
• parents/caregivers would like to continue to provide breast milk during chylothorax treatment

Exclusion Criteria:

• diagnoses of chylothorax classified as either congenital, obstructive, or traumatic not following cardiothoracic surgery
• patient has a chromosomal anomaly that affects growth (i.e. Trisomy 21, Trisomy 18 etc.)
• patient receiving less than 50% of feeds from breast milk (or mother does not have intention to provide breast milk)
• neither parent/caregiver/family member able to communicate effectively in English