The To maintain the pregnancy, placenta produces many hormones.

The stages of fetal development are
as follows:


Conception- Conception or
fertilization of an ovum by sperm takes place in the fallopian tube. During
conception, sperm penetrates into the oocyte to complete the genetic make-up of
zygote. Many mitotic divisions occur, and the zygote passes through the
fallopian tube into the uterus.

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Implantation- After one week of
fertilization, zygote attaches to the uterine wall, and the process is called
implantation. Differentiation of cell in the zygote occurs, and forms an inner
cell mass, and trophoblast. The inner cell mass develops into the embryo, and
trophoblast (outer cell mass) develops into embryonic membranes, amnion, and
placenta. To maintain the pregnancy, placenta produces many hormones. It also
carries nutrients, and oxygen from mother to fetus, and waste materials from
fetus to mother.


Embryonic stage- Cells divide
rapidly, organs and external body structures are formed. From week 3 to week 8,
nearly all organs of the embryo are formed except the brain, spinal cord, and
lungs. These 3 organs continue to form and develop until the end of pregnancy.
Most of the birth defects take place during this stage.


Development of the fetus and
placenta: Eight weeks after fertilization, the developing embryo is called a fetus.
The organs and other body structures, which were already formed, continue to develop.
The fetus fills the entire uterus, by 12 weeks. By 14 weeks, the gender of the
fetus can be identified. The movement of the fetus can be felt between 16 to 20
weeks. After about 24 weeks, the fetus is capable of surviving outside the
uterus, if intensive care is provided. The body fat reserves develop and
amniotic fluid begins to reduce by the end of 7 months.


The fetus can see and hear by the
eighth month. By month 9, the lungs are developed fully, reflexes are developed,
and the baby responds to sound, touch and light. The space is less and so, the movement
of the fetus is restricted. The fetus changes its position, and prepares itself
for labor, and delivery. The fetus is nearly 20 inches long, and weighs nearly
7 pounds. The fetus is fully developed for delivery.



Basic effects of pregnancy on
mother are described below:


Hormonal changes- During pregnancy,
placenta increases the production of hormones like estrogen, and progesterone,
which are required to maintain the pregnancy, and uterus development.


Reproductive system changes- The
rise in estrogen levels during pregnancy results in the increase in size of the
uterus. Cervix and vagina becomes more vascular. Towards the end of pregnancy, the
vagina becomes elastic, thus helping in the easy passage of the baby down the
birth canal during childbirth. The mucus in the cervix becomes thick, and thus,
protects the uterus from microbes. The breast enlarges as glands develops to
prepare for milk production.


Weight gain and nutrition- Weight
gain during pregnancy is due to increased size of uterus, placenta, amniotic
fluid, the fetus, and enlarged breasts. To ensure healthy development of the fetus,
the nutrient requirement increases during pregnancy as the metabolic rate of
the mother increases.


Digestive system changes- The uncontrollable
vomiting causes dehydration, and change in electrolyte balance. Progesterone
relaxes the smooth muscles of the stomach, and intestine, thereby, decreasing
the motility of the digestive tract. Bloating, constipation and abdominal
discomfort are generally observed. Fibrous diet is prescribed to relieve
abdominal pain and constipation.


Cardiovascular changes – The work on
the heart increases during pregnancy because more blood has to be ejected at
each beat. The heart has to pump blood through placenta, fetus, enlarged uterus,
and abdomen. The blood supply to kidneys also increases so as to remove waste
of the fetus as well.


Other effects of pregnancy on the
mother are exhaustion, congested, and bloody nose, skin discoloration, discomfort
while sleeping, shortness of breath, and mood swings.