This document discusses fetal development from conception through the three trimesters of pregnancy. It begins with definitions of fetus and outlines the germinal and embryonic stages when the fetus forms. It then describes the development that occurs in each of the three trimesters, including physical changes and growth. The document also discusses nutrition needs for the mother and fetus as well as potential pregnancy complications.

1. Made by :- Harshit Nijhawan
Class :- 12th Sci A
FETAL DEVELOPMENT

2. INDEX
1. Certification
2. Acknowledgement
3. What is fetus?
4. Formation of fetus :- Germinal and Embryonic stage
5. Development of fetus with time :- 1st, 2nd and 3rd Trimesters
6. Nutrition required during pregnancy
7. Pregnancy complications

3. Certificate
This is to certify that Mr. Harshit Nijhawan, a student of Class XII-SCI A
of Ramjas School, Pusa Road has completed the project report on
“Fetal Development” under the guidance of Mrs. Babita Gupta for the
academic year 2023-24.
This project is up to my expectations and guidelines and is to be
evaluated for the Biology Practical Examination under the Central
Board of Secondary Education (CBSE)
Examiner’s Signature Teacher’s Signature

4. Acknowledgement
Firstly, I am highly indebted to my Biology teacher, Mrs. Babita Gupta for
her guidance and constant supervision as well as for providing me with
necessary information regarding the project. I would also like to extend
my gratitude to our Principal, Mrs. Surabhi Dua for providing us with the
school lab and important requisites for the project.
Secondly, I would like to thank my parents & friends for their continued
support and coordination in this project. Lastly, I would like to express my
greatest gratitude to all those who directly or indirectly helped and
supported me throughout the project
Harshit Nijhawan

5. A fetus is an unborn offspring that develops and grows
inside the uterus (womb) of humans and other
mammals. In humans, the fetal period begins at 9
weeks after fertilization of an egg by a sperm and ends
at the time of birth.
WHAT IS
FETUS?

6. FORMATION OF FETUS
The formation and development of fetus is a part of the gestation
period.
The gestation period is divided into 3 parts
1. Germinal stage
2. Embryonic stage
3. Fetal stage
The formation takes place in the germinal and embryonic stage
whereas the development takes place in the fetal stage.

7. Germinal stage
The germinal stage of pregnancy starts at the time of conception, when the sperm and
the egg combine to form zygote.
The mitotic division starts as the zygote moves through the isthmus of the oviduct
called cleavage towards the uterus and forms 2, 4, 8, 16 daughter cells called
blastomeres. The embryo with 8 to 16 blastomeres is called a morula. The morula
continues to divide and transforms into blastocyst as it moves further into the uterus.
The blastomeres in the blastocyst are arranged into an outer layer called trophoblast
and an inner group of cells attached to trophoblast called the inner cell mass. The
trophoblast layer then gets attached to the endometrium and the inner cell mass gets
differentiated as the embryo. After attachment, the uterine cells divide rapidly and
covers the blastocyst. As a result, the blastocyst becomes embedded in the
endometrium of the uterus. This is called implantation and it leads to the embryonic
stage.

9. Embryonic stage
The embryonic stage lasts from about the third week of pregnancy until the
eighth week of pregnancy.
After implantation, finger-like projections appear on the trophoblast called
chorionic villi which are surrounded by the uterine tissue and maternal
blood. The chorionic villi and uterine tissue become interdigitated with each
other and jointly form a structural and functional unit between developing
embryo (foetus) and maternal body called placenta.
Placenta helps in:-
• exchange of O2 and CO2
• transportation of nutrients
• acts as endocrine tissue (releases hormones like: hCG, hPL, estrogens,
progestogens )

10. Immediately after implantation, the
inner cell mass (embryo)
differentiates into an outer layer
called ectoderm and an inner layer
called endoderm. A mesoderm
soon appears between the
ectoderm and the endoderm.
These three layers give rise to all
tissues (organs) in adults. It needs
to be mentioned here that the
inner cell mass contains certain
cells called stem cells which have
the potency to give rise to all the
tissues and organs.
At this stage, the embryonic development completes and now it is known as fetus.

11. DEVELOPMENT OF FETUS WITH TIME
The develpment of fetus is a long process of around 36-40 weeks.
To make the study and observation of gestation period easier, it has
been divided into 3 trimesters, i.e. :
• 1st trimester (week 1 to the end of week 12)
• 2nd trimester (week 13 to the end of week 26)
• 3rd trimester (week 27 to the end of the pregnancy)

12. 1st trimester
The week wise growth of the fetus after the embryonic period
[after implantation] is as follows:-
• Week 5: Hormone levels increases. The fifth week of pregnancy, the levels
of HCG hormone produced by the blastocyst quickly increase. This signals
the ovaries to stop releasing eggs and produce more estrogens and
progesterone which stops the menstrual period, often the first sign of
pregnancy.
• Week 6: The neural tube closes. Growth is rapid this week. The baby’s brain
and spinal cord will develop from the neural tube. The heart and other
organs are also starting to form. Small buds appear that will soon become

13. • Week 7: Baby’s head develops. Seven weeks into pregnancy, baby’s brain and
face are growing. Lower limb buds that will become legs appear and the arm
buds that sprouted last week now take on the shape of paddles.
• Week 8: Baby’s nose forms. Lower limb buds take on the shape of paddles.
Fingers have begun to form. The future shell-shaped parts of baby’s ears
develop and eyes becomes obvious. The upperlip and nose are formed and
the trunk and neck begin to straighten.
• Week 9: Baby’s toes appears. Baby’s arms grow and elbows appear. Toes are
visible and eyelids form. Head is large but still has a poorly firmed chin.
• Week 10: Baby’s elbows bend. Baby can now bend his or her elbows. Head
has become more round, toes and fingers lose their webbing and becomes
longer. The eyelids and external ears continue to develop.

14. • Week 11: Baby’s genitals develop.
Baby is now officially described as a
fetus. This week the baby’s face is
broad and the eyes are widely
seperated. Red blood cells are
beginning to form in baby’s liver. By
the end of this week, baby’s external
genitalia will start developing into a
penis or a clitoris and libia majora.
• Week 12: Baby’s fingernails form.
baby is sprouting figernails. Baby’s
face has take on a more developed
profile. His or her intestines are in the
abdomen.

15. 2nd trimester
The growth in the second trimister is as follows:-
• Week 13: Urine forms. Baby is beginning to make urine and release it into the
surrounding amniotic fluid. Baby also swallows some amniotic fluid. Bones are
beginning to harden in baby's skeleton, especially in the skull and long bones. Baby's
skin is still thin and transparent.
• Week 14: Baby's sex becoming apparent. Baby's neck has become more defined.
Red blood cells are forming in baby's spleen.
• Week 15: Baby's scalp pattern develops. Bone development continues and will soon
become visible on ultrasound images. Baby's scalp hair pattern also is forming.

16. • Week 16: Baby's eyes move. Baby's head is erect. His or her eyes can slowly move. The
ears are close to reaching their final position. Your baby's skin is getting thicker.
• Week 17: Baby's toenails develop. Baby is becoming more active in the amniotic sac,
rolling and flipping. His or her heart is pumping about 100 pints of blood each day.
• Week 18: Baby begins to hear. Baby's ears begin to stand out on the sides of his or her
head. Baby might begin to hear sounds. The eyes are beginning to face forward. Baby's
digestive system has started working.
• Week 19: Baby develops protective coating. A greasy, cheeselike coating called vernix
caseosa begins to cover your baby. The vernix caseosa helps protect baby's delicate skin
from abrasions, chapping and hardening that can result from exposure to amniotic fluid.

17. • Week 20: The halfway point. Halfway into pregnancy, the mother might be able to
feel baby's movements (quickening). Baby is regularly sleeping and waking. He or she
might be awakened by noises or your movements.
• Week 21: Baby can suck his or her thumb. Baby is completely covered with a fine,
downy hair called lanugo. The lanugo helps hold the vernix caseosa on the skin.
• Week 22: Baby's hair becomes visible. Baby's eyebrows and hair are visible. Brown
fat also is forming, the site of heat production. For boys, the testes have begun to
descend.
• Week 23: Fingerprints and footprints form. Baby begins to have rapid eye
movements. Ridges also form in the palms of the hands and soles of the feet that will
later create the foundation for fingerprints and footprints. Baby might begin
hiccuping, causing jerking movements.

18. • Week 24: Baby's skin is wrinkled, translucent and pink to red because of visible
blood in the capillaries.
• Week 25: Baby responds to your voice. Baby is spending most of his or her sleep
time in rapid eye movement, when the eyes move rapidly even though the eyelids
are closed.
• Week 26: Baby's lungs develop. Baby's lungs are beginning to produce surfactant,
the substance that allows the air sacs in the lungs to inflate and keeps them from
collapsing and sticking together when they deflate.
• Week 27: 2nd trimester ends. Baby is gaining fat, which will help his or her skin look
smoother.

20. 3rd trimester
The growth in the third trimister is as follows:-
• Week 28: Baby's eyes partially open. The central nervous system can direct
rhythmic breathing movements and control body temperature.
• Week 29: Baby kicks and stretches and make grasping movements.
• Week 30: Baby's hair grows. Baby's eyes can open wide. Red blood cells starts
to form in the bone marrow.

21. • Week 31: Baby has finished most of his or her major development. Now it's time to gain
weight quickly.
• Week 32: Baby practices breathing. The layer of soft, downy hair that has covered baby's
skin for the past few months (lanugo) starts to fall off this week.
• Week 33: Baby detects light. Baby's pupils can change size in response to a stimulus
caused by light. His or her bones are hardening. However, the skull remains soft and
flexible.
• Week 34: Baby's fingernails grow and have reached his or her fingertips.
• Week 35: Baby's skin is smooth. His or her limbs have a chubby appearance.

22. • Week 36: Baby takes up most of the amniotic sac. The mother will probably still feel
lots of stretches, rolls and wiggles.
• Week 37: Baby might turn head down. To prepare for birth, baby's head might start
descending into pelvis.
• Week 38: Baby's toenails grow. The circumference of baby's head and abdomen are
about the same. Baby's toenails have reached the tips of his or her toes. Baby has
mostly shed all of his or her lanugo.
• Week 39: Baby's chest is prominent. For boys, the testes continue to descend into
the scrotum. Fat is being added all over baby's body to keep him or her warm after
birth.
• Week 40: Due date arrives. The fetus has developed fully and is ready to enter in the
world.

24. NUTRITION REQUIRED DURING PREGNANCY
Fetal nutrients are derived largely from the mother, and fetal nutrition is thus
closely related to maternal nutrition. However, it is important to appreciate that
maternal nutrition is not the same as fetal nutrition. Firstly, the mother has her
own nutrient demands which may be in conflict with those of the fetus.
During pregnancy the mother needs folic acid, iron, calcium, vitamin D, choline,
omega-3 fatty acids, B vitamins, and vitamin C. Fortified cereal, enriched bread
and pasta, peanuts, dark green leafy vegetables, orange juice, beans are a good
source of nutrition for the mother during pregnancy.

25. PREGNANCY COMPLICATIONS
Many viral and bacterial infections can complicate a pregnancy. These include
urinary tract infections (UTIs), yeast infection, group B strep and bacterial
vaginosis. Sexually transmitted infections (STIs) can also cause pregnancy
complications. Certain infections can be passed to the fetus during pregnancy.
Problems with the placenta can interfere with pregnancy, labor and delivery.
Extreme sadness or worry during pregnancy can affect fetal development.
Preterm (early) labor is when you go into labor before 37 weeks of pregnancy.
This can cause the baby to be born at a low birth weight or with
underdeveloped organs.