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Placental Development in Pregnancy

author image Rick Rockwell
Rick Rockwell is a self-employed personal trainer and experienced freelance writer. His articles have been published throughout the Internet. He has more than eight years of experience as a certified personal trainer, group fitness instructor and lifestyle coach. His company, Rockwell Fitness, is dedicated to educating and empowering others to live healthy lifestyles.
Placental Development in Pregnancy
A pregnant woman's stomach as she holds up an ultrasound photo in front of her.

The placenta is an organ that helps provide the fetus with oxygen and nutrients. It attaches to the uterine wall in the early stages of pregnancy and grows with the fetus until birth. There are several problems that can be associated with the placenta that can lead to major complications for mother and baby.

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Placenta Identification

The placenta is a round, flat fetomaternal organ (meaning it functions for both the fetus and the mother) that develops during pregnancy and resides in the uterus with the fetus. It begins to form during week four of pregnancy. Its purpose is to nourish the growing fetus through the umbilical cord and produce pregnancy related hormones. After the birth of the baby, the placenta detaches from the uterine wall and is expelled.


Small blood vessels carrying fetal blood run through the placenta, which is full of maternal blood. Nutrient rich mother's blood moves through the placenta in order to transfer nutrients and oxygen to the fetal blood. The fetal blood transfers waste products back into the mother’s blood to be removed by the mother's kidneys--the two blood supplies never mix. The umbilical cord connects the fetus to the placenta. It has two veins carrying fresh blood to the baby and one carrying used blood back to the placenta to receive nutrients.


The placenta develops from the same sperm and egg cells that the fetus develops from. The placenta begins to develop upon implantation of the fetus into the wall of the uterus around week four of pregnancy. Microvilli (cell protrusions that increase the surface area of the cell) help to attach the placenta to the wall of the uterus. The placenta is said to have developed full maternal blood supply and attachment by the end of week 12.

Potential Problems

There are several problems related to the placenta that can be devastating for the fetus. Placenta previa is where the placenta attaches to the uterus too near or over the cervix. This can cause bleeding and trouble during labor, so medical attention is important to be sure that the placenta won't cause problems. Placenta accreta occurs when the placenta attaches too firmly to the uterine wall, sometimes causing uterine rupture or bleeding. Placental abruption is common in pregnancy and occurs when the placenta detaches either fully or partially from the uterus too early and can cause pre-term delivery or deprivation of nutrients to the fetus leading to stillbirth.


Upon delivery of the fetus, the placenta begins to detach from uterus and prepare for spontaneous expulsion called afterbirth. Commonly, the umbilical cord is cut seconds after birth and the site of the umbilical attachment to the baby at the abdomen becomes the belly button. Active management of third stage, a protocol of modern medicine to aid in the expulsion of the placenta, has dramatically reduced the potential for maternal death related to hemorrhaging and infection.

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