This document summarizes normal fetal development from the first to third trimesters of pregnancy. It describes the key physical changes that occur in each week, such as implantation in week 4, formation of the neural tube in week 6, development of the brain and face in weeks 7-8, and appearance of fingernails and genitals in weeks 11-12. The second trimester sees rapid growth, eye opening, and fetal movement. In the third trimester, the fetus gains weight and body systems further mature in preparation for birth. Fetal growth is assessed using ultrasound measurements like crown-rump length to determine gestational age.

1. Normal fetal development and
assessment of growth
Dr. Shazia Iqbal
Assistant Professor (Obstetrics & Gynaecology)
Director of Medical Education Unit
Faculty of Medicine
Alfarabi College of Medicine, Riyadh
siqbal@alfarabi.edu.sa
https://www.researchgate.net/profile/Shazia_Iqbal7
https://orcid.org/0000-0003-4890-5864

2. Outline
 First trimester
 Second trimester
 Third trimester
 Assessment of growth
 Useful Videos
 Summary

3. Firsttrimester
o Weeks 1 and 2: Getting ready
• The woman is not actually pregnant in the first week or
two of her pregnancy time. Conception typically occurs
about two weeks after the last period begins.
o Week 3: Fertilization
• The sperm and egg unite in one of the fallopian tubes to
form a one-celled entity called a zygote.
o Week 4: Implantation
• The rapidly dividing ball of cells — now known as a
blastocyst — has begun to burrow into the uterine lining
(endometrium).This process is called implantation.

5. Firsttrimester
o Week 5: Hormone levels increase
• The levels of HCG hormone produced by the
blastocyst quickly increase. This signals the ovaries
to stop releasing eggs and produce more estrogen
and progesterone. Increased levels of these
hormones stop menstrual period, often the first
sign of pregnancy, and fuel the growth of the
placenta.

6. Firsttrimester
o Week 6:The neural tube closes
• Growth is rapid this week. Just four weeks after
conception, the neural tube along the baby back is
closing. The baby's brain and spinal cord will
develop from the neural tube. The heart and other
organs also are starting to form and the heart
begins to beat.
o Week 7-8:
• Baby brain and face are growing. Depressions that
will give rise to nostrils become visible, and the
beginnings of the retinas form.
• Lower limb buds that will become legs appear and
the arm buds that sprouted last week now take on
the shape of paddles.

7. Firsttrimester
o Week 9:
• Arms grow and elbows appear. Toes are visible and
eyelids form.
• might be a little less than 3/4 inch (16 to 18
millimeters) long from
o Week10:
• head has become more round.
• baby can now bend his or her elbows.

8. Firsttrimester
o Week 11: Baby's genitals develop
• The baby is now officially described as a fetus. the
eyes widely separated, the eyelids fused and the
ears low set. Red blood cells are beginning to form
in the liver. By the end of this week, the baby
external genitalia will start developing into a penis
or a clitoris and labia majora.
• 2 inches (50 millimeters) long from crown to rump
and weigh almost 1/3 ounce (8 grams).
o Week 12:
• The fetus is sprouting fingernails. baby face now
has taken on a more developed profile. His or her
intestines are in the abdomen.
• By now fetus might be about 2 1/2 inches (61
millimeters) long and weigh about 14 grams.

9. Second
Trimester
o Week 13 to Week 16
• Growth - rapid growth continues
• Head - head has straightened up
• Musculoskeletal - ossification is proceeding
o Week 17 to Week 20
• Neural - Spinal cord myelinization begins
• Adipose Tissue - brown fat is forming
• Musculoskeletal - active movements of the fetus in
the uterus (kicks)

10. Second
Trimester
o Spleen Week 18 - alpha-SMA-positive reticulum cells
increase in number and began to form a reticular
framework. An accumulation of T and B lymphocytes
occurred within the framework, and a primitive white
pulp was observed around the arterioles.
o Hearing - Outer Ear Development week 18 - External
auditory meatus is already fully expanded to its
complete form.
o Neural - Cerebrum central sulci and opercularization of
the insula (week 18-20, GA 20-22 weeks)

11. Second
Trimester
• Week 21 to Week 25
• Vision - eyelids and eyebrows developed
• Growth - face and body are usually as they will be
at birth.
• Fetuses born after the 25th week of gestation are
generally viable

12. Second
Trimester

13. ThirdTrimester
o Week 26 to Week 29
• Vision - eyes are opened again and eyebrows and
eyelashes are well formed
• hair grows, subcutaneous adipose tissue deposits round
the whole body, becomes chubby and plump
• tooth Week 29 - Permanent premolars (correspond to the
milk molars) appear.

14. ThirdTrimester
o Week 30 to Week 34
• Integumentary - body becomes chubby and the skin is
pink
• fingernails have reached the ends of the fingers
• toenails are visible
• Genital male gonad (testes) descending W30
o Weeks 35 to 37
• Baby weighs about 5 1/2 pounds (2.5 kilograms).
• Baby has definite sleeping patterns.
• Heart and blood vessels are complete.
• Muscles and bones are fully developed.

15. ThirdTrimester
o 38 week
• The average weight of a baby at 38 weeks of pregnancy is
about 3.1kg (6.8lb), and the average length is about
49.8cm (19.6in).
• Head hair is now coarse and thicker.
• The lungs become mature during this time in preparation
for birth.

16. Assessmentof
growth
o What Is Crown-Rump Length?
• CRL may be useful in calculating gestational age. With this
gestational age, doctors can estimate potential due date.
The earlier the first ultrasound is performed, the more
accurate the baby's gestational age will be.

17. Assessmentof
growth

18. Assessmentof
growth

19. Assessmentof
growth

20. Summary
 If the assessed fetal size is within the expected range for
the duration of pregnancy, then the fetal growth is
regarded as normal.
 There are many examination to detect the age of fetus
like ultrasound (Crown rump length) and gestational age
 Each week of pregnant is important for any changes in
the fetus to know if any abnormal happen

21. Video1

22. Video2

23. References
 https://embryology.med.unsw.edu.au/embryology/index.
php/Fetal_Development#cite_note-PMID19255788-13
 https://medlineplus.gov/ency/article/002398.htm
 https://www.babycentre.co.uk/27-weeks-pregnant
 https://www.mayoclinic.org/healthy-lifestyle/pregnancy-
week-by-week/in-depth/prenatal-care/art-20045302
 https://americanpregnancy.org/healthy-pregnancy/week-
by-week/baby-development-month-by-month-48163/
 https://radiopaedia.org/cases/crown-rump-length-crl
 http://www.fpgt.unisalento.it/FPGT/images/Netherland/C
RL.png
 https://www.verywellfamily.com/crown-rump-length-crl-
2371608

24. Thank you