The placenta provides the perfect environment for your new baby.
newborn baby boy blanket
Credit: noBorders-Brandon Howies/

What Is It All About?

When you hear the word "placenta," you probably think of the cord connecting you to your baby during his time in the womb. What you may not know is that it's actually an organ, doing a lot more than providing your baby with nourishment. The placenta is also a kind of padding, and maintains a unique environment in which your baby can develop and grow. The placenta forms from the same cells as the embryo and attaches itself to the inner wall of the uterus, growing as your baby grows and the volume of your amniotic fluid increases. When it's finished growing, it is circular and weighs about a pound; when the body expels it after the birth, many women are surprised at its size and weight.

Have you ever wondered why pregnant women have to be so careful about the kinds of drugs they take? The placenta is the reason. It links your blood supply with your baby's, transferring oxygen, nutrients, and anything that enters your bloodstream directly to her. It also works in reverse, removing waste from your baby's blood to yours so it can be disposed of. The placenta also produces hormones that play a role in triggering labor, and it helps protect your baby from infections and harmful substances.

Placental Problems

Most of the time, the placenta performs perfectly. But problems can occur, particularly during the second half of pregnancy.

In some instances, the placenta gets damaged by infections or blood clots. These abnormalities can cause miscarriage, poor fetal growth, prematurity, and excessive maternal bleeding at delivery. If this happens to you, your doctor will examine your placenta after delivery and perhaps send it to a laboratory to help identify the cause of the problem. In some cases, the placenta can peel away from the uterine wall, attach too firmly, or attach in the wrong place. Sometimes vaginal bleeding alerts you to placental problems; other times, they're picked up at a routine ultrasound or exam. But bleeding is usually the hallmark of these problems, so call your doctor at the first sign of blood.

Placental Abruption

What it is: A condition in which the placenta peels away from the uterine wall before delivery, usually in the third trimester, but it can occur as early as 20 weeks' gestation.

Health dangers: Abruption can deprive the baby of oxygen and nutrients, cause bleeding in the mother, and increase the risk of preterm delivery.

Risk factors: Uncontrolled high blood pressure; smoking; use of illegal drugs (such as cocaine); abdominal trauma; abnormalities of the uterus or the umbilical cord; being older than 35; carrying multiples; premature rupture of the membranes (water breaking too early); having too little amniotic fluid.

Signs and symptoms: Vaginal bleeding, sometimes accompanied by uterine discomfort and tenderness, or sudden, continuous abdominal pain.

Diagnosis and treatment: A hospital exam and an ultrasound. If you have a mild abruption at term, your provider may recommend prompt delivery (either by inducing labor or a c-section) to avoid any risks associated with a worsening abruption. In many cases, women in the early stages of pregnancy are admitted to the hospital for monitoring. If tests show that mother and baby are doing well, the mother will receive drugs to help speed the maturation of the baby's lungs and decrease the risk of newborn complications if a premature delivery occurs.

However, if the abruption progresses, you begin to experience heavy bleeding, or the baby is having difficulties (not getting enough oxygen, for example), then prompt delivery, usually by cesarean section, will be necessary.

Placenta Previa

What it is: A low-lying placenta that covers part or all of the inner opening of the cervix.

Health dangers: The baby's exit from the uterus can be blocked during delivery. And as the cervix begins to thin and dilate in preparation for labor, blood vessels that connect the placenta to the uterus may tear, resulting in bleeding. If the bleeding is severe and occurs during labor and delivery, it can endanger the lives of mother and baby.

Risk factors: Smoking; illegal drug use; being older than 35; previous uterine surgery, such as a c-section or D&C (dilation and curettage, which involves scraping the uterine lining); carrying multiples; previous births.

Signs and symptoms: In some cases, there are no symptoms, and placenta previa is discovered during a routine ultrasound. If this occurs in the first half of pregnancy, it will most likely correct itself. During the second half of pregnancy, the condition is marked by painless vaginal bleeding.

Diagnosis and treatment: A hospital exam and an ultrasound. If the bleeding stops, as it often does, your physician will continue to monitor you and your baby. You will probably be treated with a corticosteroid to help your baby's lungs mature if you are likely to deliver before 34 weeks. At 36 weeks, if you haven't yet delivered, your provider may suggest testing the amniotic fluid (obtained by amniocentesis) to see if your baby's lungs are mature. If they are, she will likely recommend a c-section at that time to prevent risks associated with any future bleeding episodes.

If the bleeding doesn't stop, or you go into labor, your doctor will probably recommend a prompt c-section. Cesarean delivery is recommended for nearly all women with placenta previa because the birth canal is blocked by the placenta, and c-sections can usually prevent severe bleeding.

Placenta Accreta

What it is: A placenta that implants too firmly and deeply into the uterine wall. Similar conditions include placenta increta and percreta, in which the placenta breaks through the uterine wall, sometimes hitting nearby organs.

Health dangers: Premature birth or serious bleeding after vaginal delivery.

Risk factors: Having had placenta previa or previous uterine surgery.

Signs and symptoms: Vaginal bleeding during the third trimester.

Diagnosis and treatment: A hospital exam and an ultrasound, followed by a c-section and surgical removal of the placenta. Sometimes a hysterectomy is necessary. In some cases, other surgical procedures can save the uterus.

It's likely that you will not develop any placental problems. But it's best to take any steps you can to reduce your risk. And remember to call your doctor if you experience vaginal bleeding. Prompt care can lessen the chance of serious complications for you and your baby.

Richard H. Schwarz, MD, obstetrical consultant to the March of Dimes, is the vice chairman for clinical services in Maimonides Medical Center's department of obstetrics and gynecology and a professor of obstetrics and gynecology at SUNY Downstate Medical Center, both in Brooklyn.

All content here, including advice from doctors and other health professionals, should be considered as opinion only. Always seek the direct advice of your own doctor in connection with any questions or issues you may have regarding your own health or the health of others.

American Baby