Urate Crystals in a Baby's Diaper

Expert Q&A

A newborn baby boy getting his diaper changed by his father.
Newborn babies will sometimes have a orange or brick dust colored stain from urate crystals. Photo by Thanasis Zovoilis/Getty Images

Question: Yesterday our newborn baby girl had a streak of blood in the front of her diaper.

We had an appointment with a pediatrician yesterday and took the diaper along. Upon seeing that, he immediately said that it wasn't blood (which it appeared to us to be) but urine crystals reacting with chemicals in the fibers of the diaper. We had never heard of this before and it sounded rather nebulous.

As of today, she has not urinated for the last 24 hours, although had her usual wet bowel movement and there may or may not have been urine with that also. My wife is busy trying to get her in to see another pediatrician, but I wanted to know what a conservative course of action should be and if you'd ever heard of such a thing as diaper discoloration of this type.

Jeffrey, Farmer City, Illinois

Answer: Since she is not urinating very often, your pediatrician was probably right.

Urate Crystals in a Baby's Diaper

It is not uncommon to have urate crystals, which have an orange or red, brick dust color, in a newborn baby's diaper, even cloth diapers.

In fact, one study found them in the urine of 64% of newborn babies. Of course, they aren't visible on a diaper that often.

These crystals are especially common during a baby's first few days of life, when she might still be losing weight while breastfeeding, although even babies who are gaining weight well can have them.

What Causes Urate Crystals

Urate crystals are made up of uric acid, an end product of normal metabolism. Babies are born with a high blood uric acid level because of the amount they get across the placenta and this is quickly excreted in the urine and stool. If a baby is not making much urine at this time, these urate crystals will be especially concentrated and easy to see.

Keep in mind that during your baby's first week, you should expect:

  • at least 2 wet diapers and 3 bowel movements on day 2 that are likely still thick, tarry, and black (meconium)
  • at least 5-6 wet diapers and 3 bowel movements on day 3, with the BMs becoming looser and greenish to yellow in color (transitional stools)
  • at least 6 wet diapers and 3 yellow, soft and watery bowel movements on day 4

If your baby is having fewer wet diapers than expected, get your baby evaluated right away to check her weight and to see if she is feeding well.

If breastfeeding, a lactation consult might be helpful to evaluate her mother's milk supply and make sure she is latching on and sucking well.

If she is being fed baby formula, then you should make sure that you are preparing it correctly and that she is eating enough each day.


Rhodes, et al. Urinary constituents of the newborn infant. The Journal of Pediatrics.Volume 60, Issue 1, January 1962, Pages 18–23

Wilcox, et al. Abnormal serum uric acid levels in children. The Journal of Pediatrics. Volume 128, Issue 6, June 1996, Pages 731–741

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