This document summarizes the stages of human gestation from conception through birth in three trimesters. The first trimester involves major organ development, as the embryo grows to about 5cm by the end of the trimester. In the second trimester, rapid growth occurs as the fetus lengthens to about 30cm and develops further. Fetal movement becomes noticeable. In the third trimester, growth continues rapidly until birth, when the average baby weighs 3kg and measures 52cm. Premature birth is defined as occurring before 37 weeks of gestation.

1. Vihari Vichakshana Rajaguru
1st year 2nd semester
KURSK State Medical University
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2. Context
 Introduction
 Human Gestation
 First trimester
 Second trimester
 Third trimester
 After birth
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3. Introduction
 The fetal period extends from weeks
9–38, and is a time of rapid growth of
body structures established in the
embryo.
During the first half of the fetal period,
cells are still differentiating into
specific cell types to form the body’s
distinctive tissues.
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4. Human Gestation
Gestation is the carrying of
an embryo or fetus inside female viviparo
us animals, including mammals, as well
as some non-mammalian species.
Mammals during pregnancy can have
one or more gestations at the same time
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5. Human gestation is divided into
three trimesters.
Each of about 3 months duration
A. First trimester
B. Second trimester
C. Third trimester
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6. First trimester
 Main period of organogenesis ( development
of organs )
 After eight weeks the embryo develops into
the fetus and possesses all organs of the adult
in rudimentary form.
 The fetus is 5cm long at the end of the 1st
trimester.
 By the end of the trimester fetus is
recognizably human.
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7. 7
8 weeks fetus ultrasound

8. The external genital structures have
differentiated, indicating the sex of the
fetus.
Ears and eyes approach their final
positioning.
Some of the skeleton becomes distinct,
and the notochord has been replaced
by the developing vertebral column.
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9. The fetus performs breathing
movements, pumping amniotic fluid
into and out of its lungs, and even
carries on sucking movements.
By the end of the third month, the
fetus is almost 56mm long and weighs
about 14g.
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10. Second trimester
 Rapid growth occurs and the fetus is very active.
 Fetus grows rapidly about 30cm in length.
 Uterus grows sufficiently for the pregnancy to
become obvious.
 The fetal heart beat can be heard with a
stethoscope.
 Fetus moves freely through the amniotic cavity.
 5th month, the mother usually becomes aware of
fetal movements.
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11. 11
End of 5th month ultrasound
End of 6th month fetus

12. Third trimester
Growth is rapid and fetal activity
decrease.
Fetus grows to about 50cm in length
and 3 to 3.5 kg in weight.
Maternal abdominal organs become
compressed and displaced.
Final differentiation of tissues and
organs occurs.
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13.  If born prematurely during this stage, the
fetus attempts to breath and is able to move
and cry but almost always dies because its
brain is not sufficiently developed to sustain
vital functions such as rhythmic breathing
and regulation of body temperature.
 Cerebrum grows rapidly and develops
convolutions.
 Grasp and sucking reflexes are evident, and
the fetus may suck its thumb.
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14. 14
8 months old fetus

15. After birth….
After birth the average full-term baby
weighs about 3kg and measures about
52 cm in total length.
 Any infant born before 37 weeks
gestation is considered as premature.
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16. Thank you !!
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