Pregnancy Labor & Delivery What Happens When Babies Poop in the Womb Most babies don't poop until after they're born, but some will have their first bowel movement in the uterus before birth. Here's what parents should know. By Nicole Harris Updated on October 17, 2024 Medically reviewed by Wendy L. Hunter, M.D. In This Article View All In This Article Your Baby’s First Poop Why Babies Poop in the Womb Labor Interventions Meconium Aspiration Syndrome (MAS) Do Babies Fart in the Womb? Do Babies Pee in the Womb? Close FatCamera / Getty Images It's no secret babies poop a lot once they're born. But did you know that some babies poop in the womb before birth? This is only cause for concern if they inhale the fecal matter, which can lead to pneumonia, lung problems, or respiratory distress, says Jeanne Faulkner, RN, a registered nurse and author of Common Sense Pregnancy and The Complete Illustrated Birthing Companion. Learn more about a baby's first poop, why some babies poop in the womb, and what happens if they accidentally inhale it. Your Baby’s First Poop A baby's early poop is known as meconium, which is a thick, sticky, black or dark green substance almost like tar. It's made up of intestinal cells, lanugo (the downy hair some babies are born with), mucus, amniotic fluid, bile, and water, says Bradley Howard Kessler, MD, director of pediatric gastroenterology at Good Samaritan Hospital Medical Center in West Islip, New York. Most of the time, babies expel this meconium on their first day of life, usually within the first 48 hours. Sometimes, however, a baby will have their first poop in the uterus prior to birth. Baby Poop Color: What’s Normal? Once meconium passes, a baby’s poop is expected to change color, smell, and consistency. The appearance of a baby’s poop depends on whether they are breastfed or formula-fed, with breast milk poop appearing more yellow and formula poop appearing more tan. If your baby’s poop appears black, red, or white, call your child’s health care provider as these baby poop colors can indicate an issue. Why Babies Poop in the Womb Sometimes, meconium comes out when a fetus is still inside the womb, where it mixes with amniotic fluid (the liquid that surrounds the fetus in utero). Anywhere from 12% to 20% of babies poop in utero. When the baby is overdue, the number increases to around 40%. Pooping in the womb rarely happens with premature babies. Some factors that increase the risk of passing meconium in utero include: Fetal distress from inadequate blood or oxygen level Issues with the placenta or umbilical cord Going past the due date A long and hard delivery High blood pressure, diabetes, or other maternal health issues Smoking during pregnancy Poor intrauterine growth Amniotic fluid issues Preeclampsia Labor Interventions When Babies Poop in the Womb If there's meconium present during labor, your baby will be monitored more intensely to watch for signs of fetal distress. Your health care provider may also perform an amnioinfusion in cases where there's poor fetal monitoring. During an amnioinfusion, sterile fluid is placed inside the uterus through a catheter to help dilute the meconium and increase amniotic fluid volume. This procedure may be done more than once during labor if needed and may increase your baby's tolerance of labor. If your baby is still not tolerating labor well or shows other signs of fetal distress that aggressive therapy has not corrected, your provider may recommend assisted or operative delivery. This may include forceps, vacuum extraction, or a Cesarean section. Meconium Aspiration Syndrome (MAS) Meconium is actually quite clean. It consists of mostly water and doesn't cause infection of the uterus, says Faulkner. But while most fetuses who poop in the womb don't experience negative side effects, anywhere from 4% to 10% develop meconium aspiration syndrome (MAS). MAS occurs when poop is inhaled into the lungs through forceful gasps before, during, or after delivery. It can cause airway obstruction, lung inflammation, and problems with oxygen exchange. Severe or untreated MAS also increases the risk of pneumonia, collapsed lung, and other respiratory conditions in newborns. Symptoms of meconium aspiration syndrome Health care providers are trained to recognize the symptoms of meconium aspiration syndrome, and they might confirm the diagnosis with a chest X-ray after delivery. Symptoms of MAS include: Green meconium-stained amniotic fluid (Pregnant people might also notice this when their water breaks—and if so, they should tell their health care provider right away.) Meconium stains on the baby Breathing issues Bluish skin color because of low blood oxygen levels Limp body Low Apgar scores Slow heart rate (possibly detected by a fetal monitor before birth) Treating meconium aspiration syndrome Poop in the womb doesn't always call for treatment, especially if the baby appears happy and healthy after birth. However, if a newborn has MAS, health care providers will immediately suction their mouth, nose, and airways to remove the contaminated fluid. "Babies that are born not breathing, floppy, or with cardiac problems get suctioned and resuscitated until they perk up," says Faulkner. Extreme cases of MAS might require additional intervention, she adds. Depending on the specific case, this can include oxygen supplementation, breathing assistance with a ventilator, antibiotics, methods to maintain normal body temperature, IV nutrition, administration of surfactant, and nitric oxide inhalation. Babies with severe MAS might stay in the NICU, where they're watched and treated carefully, says Faulkner. Long-Term Effects of Meconium Aspiration Syndrome Most babies with MAS get better within days or weeks. Parents might notice temporarily rapid breathing , but permanent lung damage is extremely rare. And although some research shows MAS increases the risk of asthma later in life, most babies don't have any long-lasting side effects. Do Babies Fart in the Womb? While developing fetuses can poop in the womb, passing gas is another matter entirely. In order to pass gas, or "fart," you need to ingest air. Since fetuses don't take their first breath until after birth, this means farting in the womb is not just improbable, it is impossible. Do Babies Pee in the Womb? Unlike pooping, a fetus is expected to urinate in the womb. A fetus absorbs nutrients through the placenta when they're inside the womb. The waste usually exits their bodies as urine. Urine production typically begins between week 13 and week 16 of pregnancy when a fetus’s kidneys are formed. And the fetus’s urine will start to make up the majority of amniotic fluid around 20 weeks. Additional reporting by Robin Elise Weiss, PhD, MPH Updated by Anna Halkidis Was this page helpful? Thanks for your feedback! Tell us why! Other Submit Sources Parents uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy. Meconium. StatPearls. 2023. Meconium Aspiration Syndrome: An Insight. Med J Armed Forces India. 2010. Association of Apgar Score With Meconium Staining of Amniotic Fluid in Labor. Cureus. 2021. Meconium aspiration syndrome, parental atopy and asthma symptoms in children under two years old. Rev Alerg Mex. 2006.