Pregnancy fetal growth

1. Fetal- Growth, Development and
Physiology

2. Introduction
Pregnancy is measured in trimesters from the
first day of last menstural period, totaling 40
weeks
The first trimester starts from week 1 through
week12, or about 3 months
The second trimester is week 13 to week 27 &
The third trimester of pregnancy spans from
week 28 to till the birth

4. Germ cells(Oogonia) are diploid
Mitosis occurs - Maximum germ cells @ 20 wk
is 7 million
Meiosis-I occurs in primary oocyte(46 XX)
Meiosis-I gets arrested @ birth(2 million) in
late prophase
Ovaries are silent till puberty
Meiosis-I resumes @ puberty(4 lakhs)
Meiosis-I is completed @ ovulation(3 hrs
before ovulation)
End product is secondary oocyte(23X) & first
polar body
Meiosis-II occurs but it gets arrested in
Metaphase
Meiosis-II gets completed @ fertilization and
leads to formation of Mature ovum(23X) &
second polar body

5. Fertilization is fusion of sperm and mature
ovum and leads to the producion of zygote
It takes place in ampulla of fallopian tube
1st cleavage phase of zygote is 30hrs
Zygote divides and forms 16 cell stage
known as morulla
Morulla enters uterine cavity by 4-5th day
after fertilization
Now it further divided and fluid gets
accumulated to form Blastula which is the
implantation stage

6. Blastula is also called Blastocyst
Implantation site - Posterior wall of uterus near
fundus
Day of implantation - 6th day and it gets over by 10th
day
Blastocyst has an 1. Outer cell layer - Trophoblast
2. Inner cell mass - Embryoblast
Trophophoblast is the Future placenta
2 types of trophoblast - syncitiotrophoblast and
cytotrophoblast
Syncitiotrophoblast forms HCG and progesterone

7. Cytotrophoblast is the invading trophoblast
Decidua - Endometrium of pregnancy
3 types-
1.Decidua Basalis - Site of implantation
2.Decidua Capsularis - Covers zygote
3.Decidua Parietalis - Remaining portion

8. Embryoblast forms embryonic plate which divides
into Ectoderm and Endoderm
1.Ectoderm - faces amniotic cavity
It forms- Skin, Hair, Nails, Teeth, Notochord,
Neural crest, CNS, PNS & Primitive streak -
Mesoderm = vessels and connective tissue
2.Endoderm - faces yolk sac cavity
It forms- Fore gut
Mid gut and
Hind gut

9. Placenta and umbilical cord
Primary villi is finger like projection of
trophoblast (syncitio + cyto)
Secondary villi = PV + extraembryonic
mesoderm
Tertiary villi = SV + vessels in
mesoderm(vascularised trophoblast /
chorion)
Chorion -
1.Chorion Frondosum (with decidua basalis)
2. Chorion Laeve (with decidua capsularis)
Placenta = Decidua basalis + Chorion
frondosum

10. WEEKS OF GESTATION FETAL DEVELOPMENT
1 & 2  Woman is not yet pregnant
3  Fertilization
4  Implantation
5  Embryonic period begins
6  Neural tube closes & its heart starts pumping blood
7  Embryos head develops, arm buds develop and take
on the shape of paddles
8  Eyes are visible, Arms and legs are growing longer &
fingers have begun to form
9  Arms grow, develop bones and bend at the elbows
 Toes form
10  Neck begins to develop

11. WEEKS OF GESTATION FETAL DEVELOPMENT
11  Fetal genital develop
12  Fetal fingernails develop
13  Urine forms
14  Fetal sex becomes apparent
15  Fetal skeleton develops bones
16  Fetal can make sucking motions with his or her mouth
 Fetal movements are becoming coordinated and can be detected
during ultrasound
17  Fat stores begin to develop under its skin
18  Ears begin to stand out on the sides and begin to hear
19  Vernix caseosa begins to cover fetus
 Fetal uterus and vagina forms

12. WEEKS OF GESTATION FETAL DEVELOPMENT
20  Quickening
21  Fetus can swallow
22  Fetus completely covered with a fine, down-like hair
called lanugo. It helps to hold the vernix caseosa on
the skin
23  Fingerprints and footprints form
 For boys, the testes are descending from the abdomen
 For girls, uterus and ovaries are in place
24  Real hair grows
25  Fetus moves and responds to sounds
26  Fetal lungs are begin to produce surfactant
27  Fetal lungs and nervous system are continuing to
mature

13. WEEKS OF GESTATION FETAL DEVELOPMENT
28  Fetal eyes open
29  Fetal bones are fully developed
30  Fetal eyes are wide open
 Red blood cells are now forming in bone marrow
31  Nervous system development continues
32  Fetus practices breathing
 Lanugo starts to fall off
33  Fetus detects light
34  Fetus fingernails grow
35  Fetus's limbs are becoming chubby and gaining
weight rapidly

14. WEEKS OF GESTATION FETAL DEVELOPMENT
36  Fetus takes up most of the amniotic sac
37  Fetus will be considered early term
38  Fetus develops a firm grasp
39  Fetus chest become prominent
 For boys, testes continue to descend into the
scrotum
 Placenta continues to supply antibodies that willl
help fight infection after birth
40  Pregnancy due date arrives

15. Terminologies
Zygote - Collection of cells from fertilization to 2 wks
Embryo - 3 to 8 wks
Fetus - 9 wks to birth
Newborn or Neonate - Birth to 28 days
Infant - Upto 1 yr
Toddler - 1 to 3 yrs

16. Fetal Physiology
Nutrition:
Zygote- Absorption
Fetal- hematochorial
Carpus luteum provides nutrition before 6 weeks
Placenta is from 6 weeks

17. Fetal circulation:
The human fetal circulation( feto placental circulation) which includes the umbical
cord and the blood vessels within the placenta that carry fetal blood circulation of
oxygenated blood,de-oxygenated blood and the nutritive materials
Placenta: Where gas exchange takes place during fetal circulation
Umbilical cord:
2 Umbilical arteries: Carry de-oxygenated blood, fecal waste, Co2 from fetus to
the placenta
1 Umbilical vein: Brings oxygenated blood and nutrients from placenta to the
fetus

18. Three shunts of fetal circualtion:
1. Ductus venosus:
Connects the umbilical vein to the inferior vena cava
It carries oxygenated blood from the umbilical vein to inferior venacava, by passing the
liver
2. Ductus arteriosus:
Connects the main pulmonary artery to the aorta
It carries the oxygenated blood from pulmonary artery to aorta, by passing the lungs
3.Foramen ovale:
 Anatomic opening between the right and left atrium
It pushes blood from the right atrium to the left atrium

19. Oxygenated blood enters the umbilical vein
from the placenta
Enters ductus venous
Passes through the inferior venacava
Enters the right atrium
Enters the foramen ovale
Goes to the left atrium& Passes to the left
ventricle
Flows to the ascending aorta to supply the brain
and upper extremities

20. Enters the superior venacava
Goes to the right atrium and to the right
ventricle
Enters the pulmonary artery with some blood
going to the lungs to supply oxygen and
nourishment
Flows to ductus arteriosus
Enters the descending aorta with some blood
goes to the lower extremities
Enters the hypogastric arteries
Goes back to the placenta

21. Thank you