The placenta is an organ that develops in your uterus to support the fetus during pregnancy. It usually attaches to the top or the side of the uterus and grows at a rate comparable to the fetus at first. At as early as 10 weeks, the placenta can be picked up on an ultrasound. By halfway through a healthy pregnancy, it’s about 15 centimetres in diameter (the size of a side plate), and by the end it doubles to become about the size of a Frisbee and the weight of a block and a half of butter.
The placenta’s main job is to transfer oxygen and nutrients from the mother’s blood to the baby through the umbilical cord, which connects the placenta to the baby. It also transfers the baby's waste, moving gases like carbon dioxide from the baby’s blood to the mother’s.
Doctors measure the health of the placenta by looking at the health of the fetus.“We look at the baby and the blood flow through the cord,” says Edmonton-based OB/GYN Andrea Neilson. “If babies are moving and growing well, and your doctor says the pregnancy is going well, then most women don’t have to be worried about the functioning of their placenta.” Taking care of your health during pregnancy will also lead to a healthy placenta and therefore a healthy baby.
Usually, within 30 minutes of your baby’s birth, you’ll deliver the placenta in what is called the “afterbirth.” The once-essential pregnancy organ then, in most cases, goes to the incinerator. (If you were thinking of putting it in capsules and consuming it, know that experts warn against this practice, because there are no proven benefits and it can pose risks to your health and your baby's.)
There are a few rare but serious complications that can arise from an issue with your placenta.
Placental insufficiency or placenta dysfunction: This occurs when the placenta is unable to deliver an adequate supply of nutrients and oxygen to the fetus, and cannot fully support the developing baby. It brings a higher risk of preeclampsia, restricted growth or stillbirth. If this occurs, you will be monitored closely.
Placental abruption: This occurs when the placenta detaches partially or completely from the uterine wall. Doctors can sometimes pick up signs of an abruption on an ultrasound, but usually the first sign is bleeding or strong, steady contractions in the second or third trimester.
Placenta previa: When the placenta covers the cervix, it is called placenta previa. In this condition, there’s a high risk of maternal bleeding. The location of the placenta will sometimes adjust on its own as the uterus grows, particularly if the placenta was only partially covering the cervix (known as marginal placenta previa). If the cervix remains covered once the baby is full-term, you'll most likely deliver via C-section.
Placenta accreta: This is a condition in which the blood vessels of the placenta grow too deeply into the uterine wall. If you are diagnosed with placenta accreta, which is usually found during an ultrasound, your pregnancy will be closely monitored, you may be put on bed rest and, depending on the severity or how deeply the organ is embedded into the uterine wall, you may need a hysterectomy to remove the uterus entirely after your baby is born.
Retained placenta: A retained placenta is rare but it can happen if the uterus doesn’t contract sufficiently to expel the organ after birth or if the cervix starts to close before the placenta has left the body. If even a portion of the placenta remains inside the body after delivery, it can lead to infection and, often, hemorrhaging. Doctors can sometimes remove a placenta that’s refusing to come out by hand or with medication to force the uterus to contract. In some situations, surgery is required.