Day 21 The heart begins to beat
Day 28 The backbone and muscles are
forming. Arms, legs, eyes, and ears
have begun to show
Day 30 At one month old, the embryo is 10,000
times larger than the original fertilized
egg and developing rapidly. The heart
is pumping increasing quantities of
blood through the circulatory system.
The placenta forms a unique barrier
that keeps the mothers blood
separate while allowing food and
oxygen to pass through to the embryo.
Day 35 Five fingers can be seen in the hand.
The eyes darken as pigment is
The embryo begins to move spontaneously. The jaw forms, including teeth buds in the gums. Soon the eyelids will seal to protect the embryo's developing light sensitive eyes, and will reopen at about the seventh month.
At a little more than an inch long, the developing life is now called a fetus-Latin for "young one" or "offspring." Everything is now present that will be found in a fully developed adult. The heart has been beating for more than a month, the stomach produces digestive juices and the kidneys have begun to function. Forty muscle sets begin to operate in conjunction with the nervous system. The fetus' body responds to touch, although the mother will not be able to feel movement until the fourth or fifth month
At this time, the fetus is about two inches long. Urination occurs. The face has assumed a baby's profile and muscle movements are becoming more coordinated.
The fetus now sleeps, awakens and exercises its muscles
energetically-turning its head, curling its toes, and opening and
closing its mouth. The palm, when stroked will make a tight fist. The
fetus breathes amniotic fluid to help develop its respiratory system.
Fine hair has begun to grow on the head, and sexual differentiation has become apparent.
By the end of this month, the fetus is eight to ten inches in length and weighs a half pound or more. The mother will probably start to "show" now. The ears are functioning and there is evidence that the fetus hears quite a bit: the mother's voice and heartbeat as well as external noises. The umbilical cord has become an engineering marvel, transporting 300 quarts of fluids per day and completing a round-trip of fluids every 30 seconds.
Half the pregnancy has now passed, and the fetus is about 12 inches long. The mother has definitely begun to feel movement by now. if a sound is especially loud or startling, the fetus may jump in reaction to it.
Oil and sweat glands are functioning. The delicate skin of the growing baby is protected from fetal waters by a special ointment called "vernix." If the baby were born in this month and given the proper care, he would survive.