Prenatal or antenatal development refers to the process of embryonic and fetal development during pregnancy from fertilization until birth. Key stages include the pre-embryonic period from fertilization until implantation, and fetal development from 10 weeks of gestation onwards. During the pre-embryonic period, the zygote undergoes cell division and develops into a blastocyst. Implantation occurs around 6 days after fertilization. Fetal development involves the formation and growth of all major organs and systems. The fetus approximately doubles in size every month and is considered full term between weeks 36-40 of gestation.

2. Prenatal or antenatal development is the process in
which embryo or fetus gestatesduring pregnancy from
fertilization until birth.
It is also known as fetal development orembryology.
Development biology is the study of the sequences of
events from the fertilization of a secondary oocyte bya
sperm cell to the formation of an adultorganism.

4. Age of thefetus –
Gestational age is the duration of pregnancycalculated
from the first day of last menstrual period (LMP).
It is greater than the post conception (fertilization)age
by 2weeks.

5. Pre embryonic period
Also known as ovular period or germinalperiod.
Embryogenesis start with the fertilization of the egg
cell (ovum) by a sperm cell (spermatozoon). Once
fertilized, the ovum is referred to as zygote, a single
diploid cell.

6. Fertilization
Fertilization is also known as conception, is the fusion
of the sperm cell with secondary oocyte to form the
zygote.
The process takes approximately 24hrs and normally
occur in the ampulla of uterinetube.

9. The zygote divides into two cells- at 1stday
4 cells –at2 days
8by –2.5 days
16cells by- 3days. Known as morula.

10. The cells binds together tightly in a process known as
compaction.
Cavitation occur whereby the outermost cellssecrete
fluid into the morula and form blastula comprisingof
58 cells.

12. Implatation
Implantation occurs in the endometrium of theanterior
or posterior wall of the body near the fundus on 6th
day.
The blastocyst possesses an inner cell mass or
embryoblast and outer cell mass ortrophoblast.
Trophoblast- becomes the placenta andchorion.
Embryoblast- become embryo, amnion and umbilical
cord.

13. Changes or development by
weeks of gestation
1. Pre embryonicperiod-
Week 1-2– no developments occurs sincefertilization
hasn’t actuallyoccurred.
Week 3- from 15-21days, embryonic 5-7days.
Fertilization occur and formzygote.
The embryo hatches from its protein shelland
perform implantation (5-6 days).

14. Week 4th – days 22-28fromLMP
embryonic age 2weeks-
Events-
 Trophoblast cells surrounding the embryoniccells
proliferate and invade deeper into uterinelining.
 Eventually form placenta and embryonicmembrane.
 Formation of yolk sac.
 Primitive streak develop at 13days.
 Primary stem villi appears at 13days

15. Week 5
Gestational age: 4 weeks
Embryonic age: Week no. 3
A notochord forms in the center of the embryonic
disk. (day 16of fert.
gastrulation commences. (day 16of fert.)
A neural groove (future spinal cord)forms over the
notochord with a brain bulge atone
end. Neuromeres appear. (day 18of fert.)
Somites, the divisions of the future vertebra, form.
(day 20of fert.)
Primitive heart tube is forming. Vasculature begins to
develop in embryonic disc. (day 20of fert.

18. Week 6- gestational age-5 week
embryonic age 4weeks
Events –
 Embryo measures 4 mm
 The heart bulge, n begins to beat in a regularrhythem.
 The neural tube closes.
 Arm buds and tail arevisible.
 Pulmonary primordiumappear
 Hepatic plate appear
 Buccopharyngeal membrane ruptures. This form the
future mouth.
 Anterior and posterior horns differentiate in thespinal
cord.

20. Week 7-
 embryonic age 5 week
 Events-
Length is 9 mm
Lens pits and optic cupsdevelops
Nasal pits form
Brain divides into 5vessicles including the early
telencephalon.
Leg buds form.
The metanephros, precursor of kidney start todevelop.
Stomach differentiation begins.

22. Week 8-
The embryo measures 13mm (1/2 inch) inlength.
Lungs begin to form.
The brain continues todevelop.
Arms and legs have lengthened
with foot and hand areasdistinguishable.
The hands and feet have digits, but may still be
webbed.
The gonadal ridge begins to beperceptible.
The lymphatic system begins todevelop.
Main development of external genitaliastarts.

23. Week 9-
The embryo measures 18mm (3/4inch) in length.
Fetal heart tone (the sound of the heart beat) can be
heard using doppler
Nipples and hair follicles begin to form.
Location of the elbows and toes arevisible.
Spontaneous limb movements may be detected
by ultrasound.
All essential organs have at least begun.
The vitelline duct normallycloses

24. Fetal development
From the 10weeks of gestation (8th week of
embryogenic) the developing organism is called fetus.
All the major structures are already formed in the fetus
but they continue togrow.

25. Week 10 -12
Embryo measures 30–80mm (1.2–3.2inches) inlength.
Intestines rotate.
Facial features continue to develop.
The eyelids are moredeveloped.
The external features of the ear begin to take their final
shape.
The head comprises nearly half of the fetus' size.
The face is well formed
The eyelids close and will not reopen until about the 28th
week.
Tooth buds appear.
The fetus can make a fist with itsfingers.
Genitals appear well differentiated.
Red blood cells are produced in the liver

27. Week 13-16-
The fetus reaches a length of about 15cm (6inches).
A fine hair called lanugo develops on thehead.
Fetal skin is almost transparent.
More muscle tissue and bones have developed, and the
bones become harder.
Sucking motions are made with the mouth.
Meconium is made in the intestinal tract.
The liver and pancreas produce fluid secretions.
From week 13,sexprediction
At week 15,main development of external genitalia is
finished
Abdominal wall closes.

28. Abdominal wall defects

30. Week 17-21
The fetus reaches a length of 20cm (8inches).
Lanugo covers the entirebody.
Eyebrows and eyelashes appear.
Nails appear on fingers andtoes.
The fetus is more active with increased muscle
development.
"Quickening" usually occurs (the mother and others
can feel the fetus moving).
The fetal heartbeat can be heard with astethoscope.

32. Week 23-
The fetus reaches a length of 28cm (11.2 inches).
The fetus weighs about925g.
Eyebrows and eyelashes are well formed.
All of the eye components aredeveloped.
The fetus has a hand and startlereflex.
Footprints and fingerprints continue forming.
Alveoli (air sacs) are forming in lungs.

33. Week 27
The fetus reaches a length of 38cm (15inches).
The fetus weighs about 1.2kg.
The brain develops rapidly.
The nervous system develops enough to control some
body functions.
The eyelids open andclose.
The respiratory system, while immature, has
developed to the point wheregas exchange is possible.

35. Week 31
The fetus reaches a length of about 38–43cm (15–
17 inches).
The fetus weighs about 1.5kg (3lb 0oz).
The amount of body fat rapidlyincreases.
Rhythmic breathing movements occur, but lungs are not
fully mature.
Thalamic brain connections, which mediate sensory input,
form.
Bones are fully developed, but are still soft andpliable.
The fetus begins storing a lot
of iron, calcium and phosphorus

36. Week 35
The fetus reaches a length of about 40–48cm (16–
19 inches).
The fetus weighs about 2.5to 3kg (5 lb 12oz to 6 lb 12
oz).
Lanugo begins to disappear.
Body fat increases.
Fingernails reach the end of the fingertips.
A baby born at 36weeks has a high chance of survival,
but may require medical interventions

37. Week 36-40
The fetus is considered full-term at the end of the 39th
week of gestational age.
It may be 48to 53cm (19to 21inches) inlength.
The lanugo is gone except on the upper arms and
shoulders.
Fingernails extend beyond fingertips.
Small breast buds are present on bothsexes.
Head hair is now coarse and thickest

39. Thank you