Fetal development

Zygote; Blastocyst; Embryo; Fetus

Learn how your baby is conceived and how your baby develops inside the mother's womb.

Fetus at 3.5 weeks

At 3.5 weeks, the fetus will have formed the heart, begins development of the brain and spinal cord, and starts forming the gastrointestinal tract.

Fetus at 7.5 weeks

At 7.5 weeks, the eyes move forward on the face and eyelids begin to form, the palate is nearing completion and the tongue begins to form, the gastrointestinal tract separates from the genitourinary tract, and all essential organs have begun to form.

Fetus at 8.5 weeks

At 8.5 weeks, the embryo now resembles a human. Facial features continue to develop, the beginnings of external genitalia form, the anal passage opens although the rectal membrane is intact, circulation through the umbilical cord is well developed, and long bones begin to form.

Fetus at 10 weeks

A fetus at 10 weeks of development has fully formed eyelids and well-formed digits and ears.

Fetus at 12 weeks

A fetus at 12 weeks can make a fist and suck its thumb.

Fetus at 16 weeks

At week 16, the fetus reaches a length of about 6 inches, makes active movements, and makes sucking motions with the mouth.

Fetus at 24 weeks

At 24 weeks, the fetus has fully developed eyes, has a hand and startle reflex, is forming footprints and fingerprints, and is forming alveoli in the lungs.

Fetus at 26 to 30 weeks

At 26 to 30 weeks, a fetus is rapidly developing its brain controls and some body functions. The fetus has eyelids which open and close and has a rapidly developing respiratory system.

Fetus at 30 to 32 weeks

At 30 to 32 weeks, a fetus has increased central nervous system control over body functions and rhythmic breathing movements. It is still developing lungs and is partially in control of body temperature.