An Overview of Fetal Development

How Does a Fetus Develop?

The start of pregnancy is marked at the union of a woman’s egg and a man’s sperm, forming one embryo. The new embryo has the original copy of the full genetic code of a new human being. It has traits such as eye color and gender. The process is known as fertilization.

A lot of the important milestones in pre-natal development happen before birth in the first eight weeks after conception. This is when a lot of the body parts and the main body systems show up and begin to function.

embryonic-developmentDuring the first two weeks, just right after the period of a woman begins, her body starts to get ready for the possibility of pregnancy. Around 2 weeks in her cycle, the woman starts to release an egg from either one of her ovaries into the adjacent fallopian tube. Conception will now be possible during the next 24 hours and signals the start of pregnancy. The embryo has a diameter of around 4 thousandths of an inch.

In 2 to 4 weeks, the cells of the embryo continuously divide while the embryo makes its way through the fallopian tube and into the womb or uterus. The embryo then tries to embed itself into the womb lining through a process known as implantation. This begins during the end of the 3rd week and becomes completed in the 4th week of pregnancy. The embryo measures less than 1/100th of an inch in length.

How Far Along Is Pregnancy?

During 4 to 6 weeks of development, the brain starts to develop along with the heart and spinal cord. The heart starts to beat at 5 weeks and one day. It can be seen via ultrasound almost right away. At around 6 weeks, the heart starts to pump the blood of the embryo to its own body and brain. All the 4 chambers of the heart are present. By this time, more than 1 million heartbeats have happened. The head, along with the abdominal cavities and the chest are completely formed and the arms and legs start to be seen. The embryo at 6 weeks is less than ¼ of an inch long. This is often the time women contact for a free pregnancy test.

At 6 to 8 weeks there is rapid brain development and you would see appearance of the cerebral hemispheres during 6 ½ weeks. The embryo turns reflexively away when the face is touched lightly at 7 ½ weeks. There are also fingers forming on the hand. During 8 weeks of development, the embryo now measures ½ of an inch. One can easily measure conception date by ultrasound.

At 8 to 10 weeks brainwaves are measured and recorded. At 8 ½ weeks, the jawbones and collar bones start to harden. The hands move and the neck turns at 9 weeks. Hiccups also start during this time. At 10 weeks kidneys start to release urine and breathing motions start. Fingers and toes are also fully formed.

After 10 weeks, the developing individual is now called a fetus. It means “unborn offspring” or “the little one”. The eyelids are fused temporarily together at 10 ½ weeks.

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©2017 PRC Charlotte. The Pregnancy Resource Center of Charlotte is a non-profit organization providing limited medical services since 1982. Services are offered to women facing unintended pregnancies and all services free of charge.
PRC Charlotte does not perform or refer for abortions, nor arrange adoptions. Information on this website is for general education purposes only. Confidentiality is guaranteed, except as required by law.
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