If you're pregnant, you might wonder what exactly the placenta is, what it does and what might affect it. Here's what you need to know about this important organ.

The placenta is an organ that forms in the womb, also called the uterus, during pregnancy. The placenta is connected to a developing baby by a tubelike structure called the umbilical cord. Through the umbilical cord, the placenta provides oxygen and nutrients to a developing baby. It also removes waste from the baby's blood.

The placenta is attached to the wall of the uterus. Most often, it attaches to the top, side, front or back of the uterus. Rarely, it might attach in the lower area of the uterus. When this happens, the placenta may block the passage that connects the uterus to the vagina, called the cervix. If the placenta is near the opening of the cervix, it's known as a low-lying placenta. If it partly or totally covers the opening of the cervix, it causes a condition called placenta previa.

Various factors can affect the health of the placenta, including:

• Age of the pregnant person. Some conditions that affect the placenta are more common in older people, especially after age 40.
• Water breaking before labor. During pregnancy, the developing baby is surrounded and cushioned by a fluid-filled layer of tissue called the amniotic sac. If the sac leaks or breaks before labor starts, it's known as the water breaking. This raises the risk of problems with the placenta.
• High blood pressure. This condition can cause less blood to reach the placenta.
• Being pregnant with twins or other multiples. Being pregnant with more than one baby might raise the risk of some conditions related to the placenta.
• Blood-clotting conditions. Typically, blood hardens into a clump to help control bleeding from cuts. This process is called clotting. Sometimes, blood clots form inside the body and lead to medical problems. Conditions that cause blood to clot too little or too much raise the risk of some conditions related to the placenta.
• Past surgery on the uterus. C-section, surgery to remove tumors called fibroids and other uterine surgeries raise the risk of some conditions that affect the placenta.
• Previous conditions that affected the placenta. The risk of having medical issues with the placenta might be higher if you had problems with the placenta during a past pregnancy.
• Substance use. Some conditions that can affect the placenta are more common in pregnant people who smoke or use cocaine.
• Injury to the stomach area. A blow to the stomach area makes the placenta more likely to separate from the uterus too soon. Risk factors include trauma from a car accident or a serious fall.

Call your healthcare professional if you have any of the following symptoms during pregnancy:

• Bleeding from the vagina, especially if it's heavy.
• Pain in the stomach area, also called the abdomen.
• Back pain.
• Tightening and relaxing of the muscles in the uterus, also called uterine contractions.

Most medical issues related to the placenta can't be prevented directly. But you can take steps to boost your chances for a healthy pregnancy:

• Go to all of your routine pregnancy checkups.
• Work with your healthcare professional to manage any health conditions, such as high blood pressure.
• Don't smoke or use drugs. If you need help quitting, talk with your health care professional.
• If you're thinking about getting a C-section, ask your healthcare professional about the risks.

If you had a condition that affected the placenta during a past pregnancy and you’re planning another pregnancy, talk with your healthcare professional. Ask about ways to lower the risk of getting that condition again. Also tell your healthcare professional if you've had surgery on your uterus.

If you deliver your baby through your vagina, you'll also deliver the placenta that way shortly afterward. This is known as the third stage of labor.

After you give birth, you keep having mild contractions. Your healthcare professional might give you a shot of medicine called oxytocin (Pitocin). This helps you keep having contractions. It also lessens bleeding after you deliver your baby. Your healthcare professional also might massage your lower abdomen. This encourages the uterus to contract and release the placenta through the vagina. You might be asked to push to deliver the placenta.

If you have a C-section, your healthcare professional removes the placenta from your uterus during that procedure.

After it's delivered, your health care professional checks the placenta to make sure it's intact. Any pieces left behind need to be removed from the uterus to prevent bleeding and infection. If you're interested, ask to see the placenta. In some cultures, families bury the placenta in a special place.

If you have questions about the placenta during pregnancy, talk with a member of your healthcare team. Your healthcare professional can help you better understand the placenta's role in pregnancy.