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Fetal Development

Fetal Development

Author: Amanda Soderlind

This lesson will identify how a fetus develops during the second and third trimesters of pregnancy.

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Source: Video and Images Created by Amanda Soderlind

Video Transcription

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Welcome to this lesson today on fetal development.

Today we will be discussing fetal development during the second and third trimesters of pregnancy.

During the second and third trimesters, the embryo that's developing in the mother's uterus is referred to as a fetus.

So we no longer call it an embryo, but we call it a fetus.

We're going to discuss how this fetus is developing during the second and third trimesters.

The second trimester of pregnancy is from the start of the fourth month to the end of the sixth month.

The start of the fourth month to the end of the six month is considered the second trimester.

So basically, during this time of fetal development , organ and organ systems are maturing.

So organ and organ systems are maturing, and also at this point, fetal movement can be felt. So the mother is actually able to feel the fetus moving inside her.

During the third trimester. The third trimester is marked as the seventh month until birth. So from the seventh month until birth, which is around the ninth month.

During this time, organ and organ systems are continuing to mature, and the fetus is preparing for birth.

Babies who are born before the third trimester will generally have a low survival rate, because their organ systems, at that point, are too underdeveloped.

This time that it's inside the mother is very important for the organ and organ systems in order to be able to properly develop.

If it's born before that third trimester, it'll have a lower survival rate because those organ systems will not be well enough developed for the baby to be able to survive independently.

OK. The circulatory system of a fetus is composed of temporary vessels and lungs that do not function while it's in the uterus.

So while the fetus is within the uterus, gas exchange is not occurring. So the lungs at that point are not functioning, because the placenta is playing the role of delivering oxygen to the fetus, and removing carbon dioxide.

So the fetus is not actually breathing. Its lungs are not functioning while it's in the uterus.

But once the baby is born, the circulatory system then becomes independent, and the lungs will began gas exchange when the first breath is taken.

So while the fetus is within the mother, the circulatory system is kind of depending on the mother, and the lungs are not functioning. But once the baby is born, that circulatory system becomes independent, and then the lungs are able to actually begin gas exchange at that point, as well.

This lesson has been an overview on fetal development during the second and third trimesters of pregnancy.

Terms to Know
Second Trimester

Marks the start of the 4th month until the end of the 6th month of pregnancy in which the fetus continues to develop as organs and organ systems mature.

Third Trimester

Marks the 7th month of pregnancy until birth, and is characterized by the continued development of the fetus as it prepares for birth.