Do Babies Pee In The Womb?

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Babies Pee Womb

Feeling your developing baby wiggle and kick in the womb is a fun aspect of pregnancy for many parents-to-be. Week by week, as you read about new developments and feel the movements, this fetus you’re carrying may start to feel more like a person. Which invites some potentially awkward questions–like, what happens when my unborn baby needs to pee?

Gross pregnancy news of the day: Babies absolutely pee in the womb.

My Baby Does What?

Peeing in utero starts earlier than you might expect, as early as about eight weeks’ gestation. By weeks 13 to 16, the renal system is developing rapidly, which means those brand-new kidneys are testing out what they can do. As in, produce urine. Yes, your baby is peeing inside the womb for about 25 weeks or so out of the 40 weeks of your pregnancy.

In order to produce urine, your baby needs to ingest fluid. Fetuses spend most of their time in utero sleeping (90-95% of the time, for much of your pregnancy). When they’re awake, one of the ways they pass the time is by practicing swallowing. Developing the necessary muscles and reflexes to suck and swallow ensures that your baby will be ready to take in nourishment from milk after birth. Your baby is floating in amniotic fluid, so that’s what he or she practices swallowing.

You’ve probably made the connection: Swallowing amniotic fluid, peeing it out, and swallowing more essentially guarantees that your baby will swallow some of his or her own urine before birth. Some sources estimate that by week 20, about half of your amniotic fluid is fetal urine. Your medical provider may look at amniotic fluid volume to assess whether your developing baby is peeing enough.

Is That Safe?

Imagining your developing baby swimming in pee isn’t exactly the glowing image you had for pregnancy. Fair enough. Let’s at least put any concerns to rest.

The urine your baby produces in utero doesn’t pose any risks, even when the fetus consumes it. It’s not only normal, but healthy for your baby’s body to run organ system function, as well as develop swallowing and other actions needed for survival. Your body creates an ideal environment to protect the baby as it develops. Temperature control, nutrients, antibody protection, and more are just a few of the automatic benefits your baby gets automatically in the womb. The germ situation isn’t comparable to, for example, a toddler dipping a sippy cup in the toilet (even “unused” water!).

Does My Baby Poop in the Womb, Too?

At this point, you might be biting your nails and wondering, “If my baby’s peeing in the womb, is she pooping, too?”

You can let out a deep breath for this one. Chances are high that your baby isn’t having bowel movements before birth. The umbilical cord provides the nutrients a developing fetus needs, so the baby doesn’t take in excess or waste material the way we do when we eat regular food.

There are some small solid components floating around in the amniotic fluid, such as loose hair, dead skin cells from the fetus or the uterine lining. The fetus swallows some of this over time, and these materials turn into the black, sticky meconium that becomes your baby’s first bowel movement after birth. Generally, babies hold it until they’re out in the world (a feat they won’t repeat until potty-training time, unfortunately). Sometimes, babies pass meconium before or during the labor and birth process. This can be dangerous if the baby inhales some of the meconium, but your medical team will take steps to prevent or treat signs of respiratory distress.

Jessica Sillers
Jessica Sillers is a parenting and finance writer whose work has been featured in Pregnancy & Newborn, Headspace, and more. As a new mom herself, she’s passionate about helping other parents find the community and support they need. When she’s not writing, she loves spending time with her family, reading, and hiking.

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