Characteristics of the Unborn Child

Prenatal Age: 2 – 4 Weeks Post-LMP
Up to 2 weeks following Conception

The cells of the embryo repeatedly divide as the embryo moves through the fallopian tube into the woman’s uterus or womb. 

Implantation, the process whereby the embryo embeds itself into the wall of the womb, begins by the end of the third week and is completed during the fourth week of pregnancy.

At 4 weeks, the embryo is less than 1/100th of an inch long.

Prenatal Age: 4 – 6 Weeks Post-LMP
>2 – 4 Weeks Post-Conception

By 5 weeks, development of the brain, the spinal cord, and the heart is underway. The heart begins beating at 5 weeks and one day and is visible by ultrasound.

By 6 weeks, the heart is pumping blood. All four chambers of the heart are present.

The head, as well as the chest and abdominal cavities have formed and the beginnings of the arms and legs are visible. At 6 weeks, the embryo measures less than ¼ of an inch long.

Prenatal Age: 6 – 8 Weeks Post-LMP
4-6 Weeks Post-Conception

At 6 ½ weeks, rapid brain development continues with the appearance of the cerebral hemispheres.

At 7 ½ weeks, the embryo reflexively turns away in response to a light touch on the face.

Fingers are beginning to form.

The embryo is about ½ inch at 8 weeks.



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