The placenta is the crucial connection between the fetus and the mother. Throughout the pregnancy, it carries out all the biological functions that fetuses can’t do for themselves yet. After attaching itself to the uterine wall, the placenta connects to the fetus via the umbilical cord. Here are the functions of the placenta:
- Supplies nutrients and oxygen — the placenta delivers nutrients, supplies oxygen, and transfers carbon dioxide from the baby back to the mother’s blood supply.
- Eliminates waste — waste produced by the fetus, such as urea and uric acid, is absorbed back into the mother’s blood via the placenta by the process of diffusion.
- Produces pregnancy hormones — the placenta produces a number of hormones throughout pregnancy, each of which plays an important role in supporting the pregnancy.
– HCG hormone maintains the corpus luteum — an important temporary gland in the ovaries, which produces progesterone. If you don’t become pregnant, this cell group dies off every month a few days after ovulation, causing menstruation. If you do become pregnant, the hCG produced by the placenta tells this cell group to sustain the pregnancy, maintain the uterine lining, release hormones, and more. hCG is also the hormone detected by pregnancy test kits.
– Progesterone helps with the implantation of the fetus and creates a rich uterine lining of blood vessels to provide nutrition to the baby as it grows.
– Estrogen promotes breast and milk duct development in the mother.
– Human placental lactogen, or hPL, stimulates the fetus’s growth and development.
- Provides immunity — the body’s infection-fighting antibodies, called immunoglobulins (mostly IgA and IgG), can pass from the mother to the fetus through the placenta. This not only protects the fetus from infections while in the womb but also provides immunity to the baby for around three months after delivery.
- Filters out microorganisms — although the placenta can filter out some microbes, it is not a perfect infection or toxin barrier. That’s why doctors tell pregnant women to avoid possible sources of infections and toxins (e.g. nicotine, alcohol, and drugs).
- Regulates the fetus’s body temperature
About 10 days after conception, as soon as the fertilized egg implants in the uterus, chorion forms. Chorion is an embryonic organ which precedes the placenta’s development.
Placenta fully develops by week 18–20 of pregnancy, but it continues to grow to support the baby’s oxygen, growing nutrition, and immunity needs. The mother’s blood supply is fully connected to the developing placenta by week 14 of pregnancy.
The anatomy of the placenta consists of two components:
- Maternal placenta — this part of the placenta develops from the mother’s uterine tissue and starts forming 7–12 days after conception.
- Fetal placenta — this is formed when the outer cells of the blastocyst (a mass of cells making up the earliest form of the embryo) divide and burrow deep into the uterus to connect to the mother’s blood supply. This part of the placenta starts forming 17–22 days after conception.
When does the placenta take over?
At the beginning of pregnancy, a group of cells in the ovaries called the corpus luteum is responsible for producing the necessary estrogen and progesterone. However, once the placenta becomes fully developed at 18–20 weeks, it can take over production, and the corpus luteum dissolves. This process is known as the placenta “taking over.” Many women experience reduced morning sickness and more energy once the placenta takes over, usually in the second trimester.
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The placenta attaches and develops wherever the fertilized egg implants in the uterus. The placement of the placenta can vary, but here are a few of the more common positions:
- Posterior placenta — In this case, the placenta grows at the back of your uterus wall, where the fertilized egg attached.
- Anterior placenta — This is when the placenta attaches in the front wall of the uterus, and the fetus grows behind it.
- Fundal placenta — This happens when the placenta attaches and grows on the top wall of your uterus.
- Here are rarer, abnormal positions of attachment:
- Placenta praevia — This is a rare case when the placenta attaches towards the lower end of the uterus, either partially or fully (complete placenta previa) covering your cervix. This is also called a low-lying placenta. It’s more common in early pregnancy and might resolve as the fetus grows larger. If not resolved, it can cause severe vaginal bleeding during pregnancy or labor. Your doctor will help you determine what to do next if you have a low-lying placenta.
- Placenta accreta — This is when the placenta attaches to the underlying uterine wall.
- Placenta increta — This is when the placenta extends into the myometrium, the muscular layer of the uterus.
- Placenta percreta — This when the placenta pushes through the myometrium and serosa and potentially disrupts adjacent organs.
The placenta might also shift positions as the pregnancy progresses, moving upwards into the womb as the baby descends lower.
Why the health of the placenta is so important
Throughout your pregnancy, the placenta plays a crucial role in making sure that the baby grows and develops normally. Supplying nutrition and oxygen, transferring waste, protecting the fetus from infections — it does it all! Behind a healthy baby is a healthy placenta. Here are a few tips for maintaining a healthy placenta throughout your pregnancy:
- Eat a healthy, balanced diet — lots of fresh vegetables and fruits, and fewer processed, sugary, and fried foods.
- Exercising regularly during pregnancy can boost your body’s oxygen supply. Swimming, walking briskly, and practicing low-impact aerobics are generally safe during pregnancy.
- Take part in stress-releasing activities such as meditation and spending time with loved ones. Research has shown that stress hormones can pass from the mother to the baby through the placenta, which why staying calm helps.
- Avoid smoking. Studies have linked smoking to poor placental health, low birth weight, sudden infant death syndrome, and childhood respiratory illnesses.
- Avoid alcohol. Studies have shown that drinking alcohol while you’re pregnant increases the risk of placental abruption when the placenta separates from the uterus before birth. This can deprive the baby of oxygen and nutrition, harming their health.
As soon as the fertilized egg attaches to the uterine inner lining (the endometrium), the placenta begins to develop. The placenta plays a crucial role in ensuring a healthy pregnancy. It performs several functions that fetuses can’t do for themselves yet. Supplying nutrition and oxygen, removing waste materials and gases, producing pregnancy hormones, protecting the fetus from infections — the placenta does it all.
The placenta is usually expelled from the body shortly after birth. In rare cases, part of it may not be expelled naturally, requiring urgent intervention. Your doctor will help you keep track of the position and health of your placenta.