6 Week Unborn Baby

SourceThe Endowment for Human Development ()

The embryo has brainwaves by 6 weeks, 2 days!

From 6 to 6½ weeks, the cerebral vesicles will double in size. Individualized brainwaves recorded via electroencephalogram (e-lek’tro-en-sef’a-lo-gram), or EEG, have been reported as early as 6 weeks, 2 days.

Also by 7 weeks, cell groupings resembling taste buds appear on the tongue and hiccups begin. Nasal plugs are prominent at this time and will persist for another 6 weeks or so.

By 7 weeks, the heart has 4 chambers.

The pacemaker center is already well-established in the right atrium. The embryonic heart rate peaks at 7 weeks and now beats approximately 167-175 times per minute. This rate gradually declines to about 140 beats per minute at birth.

By 6½ weeks, the elbows are distinct and the embryo begins moving both hands. The fingers are also starting to separate as evidenced by the appearance of notching between the digital rays.

The foot plate and ankle also emerge while toes and metatarsal (met’a-tar’sal) bones begin to form in the feet. Joint development is underway and the onset of primary muscle fiber formation indicates the embryo’s muscles are growing.

The hands and feet change dramatically between 6 and 7 weeks as separate fingers and toes begin to emerge. At 6 weeks the hand plates develop a subtle flattening between the digital rays. By 6 weeks, 2 days the hand takes on a polygon shape; prominent notches appear between the digital rays by 7 weeks and individual fingers are fully separated by 7½ weeks.

Bone formation begins between 6 and 7 weeks, starting with the clavicle, or collar bone, and the upper and lower jaw. This process is called ossification. Also, by 7 weeks, the embryo moves the legs and exhibits a startle response.

The immune system is maturing, as evidenced by the presence of B-lymphocytes in the liver. After birth and relocation away from the protection of the womb, these lymphocytes will produce proteins called antibodies to fight infection.

By 7 weeks, the ovaries appear in the female embryo. In the male embryo, a gene on the Y-chromosome produces a substance causing the testes to begin to differentiate.