Supplemental nursing system
The supplemental nursing system (SNS) consists of a container and a capillary tube leading from the container to the mother's nipple.
The tubing is usually attached with removable tape. When the newborn infant suckles on the breast, the infant is nourished both by fluid from the capillary tube and by the mother's breastmilk from the nipple. The mother's milk supply is stimulated by the infant suckling, and in most cases the use of the SNS can be discontinued in a few days or weeks when the mother's milk supply has risen to meet the infant's needs. Mothers usually obtain SNS supplies from a lactation consultant.
Reasons for use 
A supplemental nursing system is used by breastfeeding mothers for different reasons
Reasons concerning the baby 
- hyperactive or hypertonic baby
- baby has a weak suck
- baby has a poor latch
- baby who loses more than 10% of birth weight and is at risk for jaundice or hypoglycemia
- premature baby who has to get lot of calories in minimum of time because he is quickly exhausted
- baby was separated from mother and milk supply is poor
- baby with Down syndrome or Pierre Robin syndrome
- baby with cleft lip, cleft palate
- baby with congenital heart disease (CHD)
- baby who has a failure to thrive (FTT)
Reasons concerning the mother 
- mother has an adopted child and wishes to induce lactation
- mother has been separated and has to stimulate lactation
- mother has had breast surgery and subsequent impaired lactation
- mother has a hormonal problem and insufficient lactation
- mother has flat or inverted nipples which makes it difficult for baby to latch
Advantages of supplementing by SNS 
When an SNS is used, it is still feeding breastmilk, the device ideally helps coming back to exclusive breastfeeding. Mother and baby are in close (possibly skin to skin) contact which helps lactation hormones to act ; oxytocin for milk rejection effect and for bonding, prolactin for milk synthesis. The rule is, like for breastfeeding : look for feeding cues in baby, and feed on demand.