Pre- and Post-Breastfeeding Weight Checks: When, Why, and How to Do Them Correctly
Weighing a baby before and after a feeding—can be a useful tool in lactation care. But it’s not something every breastfeeding dyad needs. When used appropriately, pre- and post-feed weight checks can provide valuable insight into milk transfer. When used excessively or with improper technique, they can cause unnecessary anxiety.
When Should You Do Pre- and Post-Feed Weights?
• Concerns about milk transfer – If a baby is struggling to gain weight, feeding frequently but still showing signs of inadequate intake, or has signs of ineffective sucking.
• Premature or medically fragile infant– Babies with medical conditions may need closer monitoring to ensure they’re taking in enough milk.
• Suspected low supply or oversupply – Understanding how much milk a baby is transferring can help guide supplementation or block feeding strategies.
• Tracking feeding progress – In cases where parents need reassurance that their baby is getting enough, occasional test weights can provide peace of mind.
How to Perform a Pre- and Post-Feed Weight Check
1. Use a highly sensitive, hospital-grade scale – The scale should measure in grams, not just ounces, to detect small changes.
Why Precision Matters: Choosing the Right Scale
A hospital-grade scale with accuracy to 2-5 grams is essential because breastfed babies often transfer small but meaningful amounts of milk, especially in the first 3-4 weeks after. Since 1 gram = 1 mL of milk, a scale that only measures in ounces (where 1 oz = ~28.35 grams) lacks the precision needed to assess intake accurately. For example, if a baby transfers 20 mL (20 grams), a scale that rounds to the nearest 0.5 oz (15 grams) or full ounce (30 grams) may fail to detect intake entirely or overestimate by nearly 50%, leading to unnecessary concern or false reassurance. A highly sensitive scale ensures accurate tracking and better feeding decisions. The reason I prefer grams is the calculation is much more complicated when in pounds and ounces since it’s a scale of 16. If your scale says 6.5 pounds, that’s not 6 pounds 5 ounces. That’s 6 pounds and half a pound which is 8 ounces. Like when you order turkey at the deli. A quarter pound is 4 ounces. Your scale needs to acyuallly say pounds and ounces. And even then, that’s too much math for my brain.
2. Weigh baby in just a dry diaperClothing, blankets, and even a hat can change the reading.
3. Take the pre-feed weight – Place baby on the scale before feeding and record the weight in grams.
4. Breastfeed as usual – No adjustments, just a normal feeding session.
5. Take the post-feed weight – Weigh baby again immediately after the feed, using the same conditions (same dry diaper, no clothing added or removed).
6. Calculate the intake – The difference between the post-feed and pre-feed weights in grams equals the amount of milk transferred in milliliters (1 gram = 1 mL of milk). So let’s say the scale says 3.500 grams before baby feeds and then 3.560 grams after baby feeds. 3.560 minus 3.500 is 60. So the baby took 60grams. 30 grams is 1oz.
Things to Keep in Mind
• One feeding is just one data point – Milk intake varies throughout the day, so a single test weight doesn’t tell the full story.
• Not every baby needs it – If a baby is gaining well, feeding effectively, and meeting milestones, routine pre- and post-feed weights aren’t necessary.
• Weight fluctuations are normal – A few grams of variation from movement, diaper wetness, or scale sensitivity is expected
Pre- and post-feed weight checks are a valuable tool when used appropriately, but they should always be interpreted in the context of the baby’s overall growth, diaper output, and feeding behaviors. When in doubt, working with a skilled lactation consultant can help determine if and when they’re needed!