Placenta

The placenta is a temporary organ that develops inside the uterus during pregnancy. It attaches to the wall of the uterus and connects to the baby through the umbilical cord. Its job is to deliver oxygen and nutrients from the pregnant person's blood to the baby, and to carry waste products away. After the baby is born, the placenta is delivered too — which is why it's sometimes called the "afterbirth."

• The placenta develops during pregnancy and is the baby's life-support system.
• It delivers oxygen and nutrients to the baby and removes waste, all through the umbilical cord.
• It also produces hormones that maintain the pregnancy.
• It's attached to the wall of the uterus and is delivered after the baby during birth.
• The placenta acts as a filter, but it doesn't block everything — alcohol, some drugs, and certain infections can cross it.

[DIAGRAM: Diagram of pregnant uterus showing placenta attached to uterine wall, umbilical cord, and foetus]

How it works

The placenta starts forming shortly after a fertilised egg implants in the uterus lining. It grows alongside the baby and is fully functioning by about 12 weeks of pregnancy. It's a disc-shaped organ, roughly 20-25cm across by the end of pregnancy, and it's rich with blood vessels.

The clever bit is that the pregnant person's blood and the baby's blood don't actually mix. They flow very close together inside the placenta, separated by thin membranes. Oxygen and nutrients pass from the parent's blood into the baby's, and waste products (like carbon dioxide) pass the other way. The baby's blood then flows back through the umbilical cord.

The placenta also produces hormones — including progesterone and human chorionic gonadotropin (hCG, the hormone pregnancy tests detect) — that keep the pregnancy going and prepare the body for birth and breastfeeding.

Why it matters

The placenta is why pregnancy advice includes avoiding certain things. While it filters out a lot, it doesn't block everything:

• Alcohol crosses the placenta freely, which is why drinking during pregnancy can affect the baby's development.
• Nicotine and carbon monoxide from smoking cross the placenta, reducing oxygen to the baby.
• Some medications and recreational drugs can cross it too.
• Certain infections (like rubella, toxoplasmosis, and some STIs) can pass through.

This isn't about judging anyone — it's about understanding that the placenta is a filter, not an impenetrable wall.

After birth

The placenta is delivered shortly after the baby — usually within 30 minutes. This is sometimes called the "third stage of labour." The midwife checks it's complete, because any placental tissue left behind can cause problems like infection or heavy bleeding.

Things people ask about the placenta

What does the placenta look like?

It's a flat, round, dark red organ about the size of a dinner plate, with the umbilical cord attached to one side. It looks like a large piece of organ tissue — which is exactly what it is.

Can the placenta cause problems during pregnancy?

Sometimes. Placenta praevia is when the placenta sits low in the uterus, covering the cervix — which can cause bleeding and may require a caesarean delivery. Placental abruption is when it separates from the uterus wall too early, which is a medical emergency. Both are monitored during pregnancy through scans. [CHECK: current screening protocols]

Do people really eat the placenta?

Some people choose to — usually dried and put into capsules. There's no scientific evidence that this has health benefits, and some health bodies advise against it. [CHECK: current NHS/RCOG position on placentophagy]

The placenta is a special organ that grows inside the womb during pregnancy. It attaches to the wall of the womb and connects to the baby through a cord called the umbilical cord.

Its job is to keep the baby alive and growing. It takes oxygen and food from the pregnant person's blood and passes it to the baby. It also takes waste away from the baby. The parent's blood and the baby's blood don't actually mix — they flow very close together inside the placenta, with thin walls between them.

The placenta also makes hormones that keep the pregnancy going. One of these hormones is what pregnancy tests pick up.

The placenta acts like a filter, but it doesn't block everything. That's why pregnant people are told to avoid alcohol and certain medicines — these things can pass through the placenta and affect the baby.

After the baby is born, the placenta comes out too. This usually happens within about half an hour. It's sometimes called the afterbirth.

By the end of pregnancy, the placenta is about the size of a dinner plate. It's flat, round, and dark red.