Definition - What does Fetus mean?

A fetus is a term which refers to the unborn offspring from the end of the 8th-week post-fertilization or the 10th week of pregnancy up until the birth. Many of the vital organs, including the brain, kidneys, and liver, have already begun to form.

In order to reach the fetal stage, the egg which is released from the ovaries must be fertilized by sperm and implant into the uterine wall. This can occur both through intercourse and assisted reproductive technologies.

FertilitySmarts explains Fetus

Upon fertilization, the resulting structure is referred to as a zygote which travels down the fallopian tube to the uterus, dividing as moves, forming what is known as a blastocyst. Once it gets to the uterus, the blastocyst attaches itself to the wall and is later implanted in the uterus. During this time, it is referred to as an embryo, which is roughly around the 3-week mark. It continues to grow, and upon reaching the 8-week mark, it is called a fetus.

During the fetal period, the structures which have already begun to form, continue to develop, and several milestones need to be reached for the successful growth of the fetus.

Between weeks 11 and 14
•The genitals begin to form
•The tooth buds appear
•The fetus’ liver makes red blood cells

Between week 15 and 18
•The fetus begins to move around
•The liver and pancreas begin to produce secretions

Between week 19 and 22
•The fetus begins to hear
•The fetus is able to swallow
•The fetus' heartbeat can be heard with a stethoscope

Between weeks 23 and 26
•The bone marrow begins to make blood cells
•All parts of the eyes are developed

Between weeks 27 and 30
•The brain begins to grow more rapidly
•The lungs begin to produce surfactant

Past 30 weeks, the baby continues to develop and usually positions itself in a head-down direction in preparation for birth. At that time, 98% of the babies born will survive, although they would be described as premature.

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