A supplemental nursing system (SNS) is a device that delivers extra milk to your baby while they nurse at the breast. It consists of a small container, usually a bottle or bag, filled with expressed breast milk or formula. A thin, soft tube runs from the container to your nipple, so your baby receives the supplement and your breast milk simultaneously during a normal feeding. The system lets you supplement without ever reaching for a bottle.
How the Device Works
The container hangs from a cord around your neck, and the thin silicone tube is taped along your breast with medical tape so the tip sits right at your nipple. When your baby latches onto both the breast and the tube, their sucking draws milk through the tubing. Milk only flows when the baby is actively latched and sucking, which keeps feedings tidy and mimics the natural rhythm of breastfeeding. You can tell the system is working correctly when you see small bubbles rising up into the container each time your baby swallows.
Because the supplement travels along your skin before reaching your baby’s mouth, it warms to body temperature on the way. This makes the feeding feel more natural for both of you compared to switching between breast and a cold bottle.
Who Benefits From an SNS
The most common reason parents turn to a supplemental nursing system is low milk supply. Whether supply dipped after a difficult start, a medical condition, or a period of separation from the baby, the SNS lets you feed your baby enough while your body catches up. Every time the baby sucks at the breast, it sends signals to produce more milk, so supplementing at the breast actively works to increase your supply in a way that bottle-feeding cannot.
Parents who are relactating (restarting milk production after a gap) or inducing lactation for an adopted baby also use an SNS. In these situations, the baby’s sucking is the primary tool for building a milk supply from scratch, and the supplement keeps the baby fed and motivated to stay at the breast during the process. The system is also helpful for babies who are premature, have a weak suck, or need extra calories to gain weight but still benefit from time at the breast.
Why It’s Preferred Over Bottles
The core advantage of an SNS is that it keeps the baby at the breast. Switching between breast and bottle can sometimes cause a baby to develop a preference for the faster, easier flow of a bottle nipple, making them fussy or refusing the breast altogether. With an SNS, every feeding reinforces the breastfeeding relationship.
There’s also a hormonal benefit. The physical stimulation of a baby sucking at the breast triggers the release of the hormones responsible for milk production. A bottle bypasses this entirely. So for anyone trying to build or rebuild supply, an SNS does double duty: it feeds the baby now and helps produce more milk for later.
What You Can Put in the Container
The system works with expressed breast milk, donor breast milk, or infant formula. Many parents start with formula while they work on increasing their own supply, then gradually shift to expressed milk as production rises. If you use formula, ready-to-feed liquid formula is a better choice than powdered, because powder is more likely to clog the narrow tubing.
How Long You’ll Use It
The timeline depends on why you’re using the system. For relactation, a general guideline is that rebuilding supply takes roughly as long as the gap since breastfeeding stopped. About half of parents who successfully relactate reach a full milk supply within a month. Others take longer or continue supplementing with some formula alongside breastfeeding.
If you’re using the SNS because of a chronic low supply or a medical condition, you may use it for a longer stretch. There’s no set deadline. The goal for most families is to gradually reduce the amount of supplement in the container as the baby gets more from the breast itself. A lactation consultant can help you track intake and know when to decrease the supplement.
Setting It Up and Getting a Good Latch
Position the tube alongside your nipple as your baby latches. Some babies take to it immediately; others need a little coaxing. If your baby seems bothered by the tube touching the roof of their mouth, try placing it along their tongue instead, or slip it into the corner of their mouth after they’ve already latched. You can also start the feeding at the breast without the tube, then introduce it once your baby’s swallowing slows and they need the extra flow.
If your baby is reluctant to latch at all, try the opposite approach: start with the supplementer so they’re rewarded with milk right away, which encourages them to stay on.
Controlling Milk Flow
Your baby still needs to actively suck for the system to work properly. If milk flows too fast, it can overwhelm the baby and reduce the effort they put into feeding, which defeats the purpose of stimulating your supply. You can adjust the flow in a few ways:
- Change the container height. Raising the bottle speeds flow; lowering it slows things down.
- Try different tubing sizes. Narrower tubing delivers milk more slowly.
- Pinch or clamp the tube. This gives you moment-to-moment control during a feeding.
Watch your baby’s cues carefully. If they’re gulping, pulling away, or seem stressed, the flow is likely too fast. This is especially important for premature babies or those with any health concerns.
Cleaning and Maintenance
After each feeding, flush the tubing with cold water using a small syringe to prevent milk from drying inside. Then wash everything with hot soapy water, rinse well, and let it air dry completely. If you’re using nasogastric-style tubes (the kind found in some DIY setups), these aren’t designed for repeated sterilization and should be replaced roughly every week, or sooner if the tubing feels stiff.
Keeping the system clean does add time to your routine, and many parents find this the most challenging part of using an SNS. Having a second set of tubing ready to go can make the process less stressful, especially for nighttime feedings when the last thing you want to do is stand at the sink with a syringe.
Getting Started With Professional Support
An SNS is simple in concept but takes practice to use smoothly. Most families benefit from hands-on help from a lactation consultant (IBCLC) the first few times. A consultant can make sure the tube is positioned correctly, check your baby’s latch, adjust the flow rate, and create a plan for gradually reducing the supplement as your supply grows. Many hospitals, birth centers, and pediatric offices have lactation consultants on staff or can refer you to one in private practice.