Pregnancy and lactation tute prescription

1. Physiology of Pregnancy
Prof. Sudharshani Wasalathanthri
Department of Physiology
AL/2019

2. In this lecture
1. Fertilization and implantation
2. Placenta and fetoplacental unit
3. Placental and fetal circulations
4. Hormone secretion during pregnancy
5. Changes in maternal organ systems during
pregnancy

3. Fertilization
Millions of sperms deposited in vagina during coitus
Chemoattraction by substances secreted by ovum
(50 – 100)
Binding of sperms to sperm receptors in zona pellucida
Penetration of corona radiata
Acrosome reaction and penetration of zona pellucida

4. ONE sperm reaches ovum membrane
Fuses with ovum membrane (mediated by fertilin on sperm head)
Sperm nucleus is released to the ovum cytoplasm
Fusion of nuclei
23
chromosomes
23
chromosomes
46 chromosomes
Zygote

6. Fertilization usually occurs in the ampulla of the uterine tube

7. Events after fertilization

8. Fate of the fertilized ovum
• Fertilized ovum is transported into uterine cavity
in 3 - 5 days
• Continues division and forms blastocyst
Blastocyst
Inner cell mass
Forms foetus
Along with the
endometrium
Forms Placenta
Outer cell mass
(trophoblast)

9. Implantation
- Occurs when the blastocyst comes in contact
with the endometrium.
- Commonest site of implantation –
upper posterior part of uterine cavity

10. Changes in the corpus luteum
• Corpus luteum fails to regress and starts enlarging once
the ovum is fertilized
• ‘Corpus luteum of pregnancy’
• Secretes oestrogen, progetsrone and relaxin (maintains
pregnancy by preventing myometrial contractions)
• After 6th week the function of corpus luteum declines
(taken over by placenta)

11. Placenta – organ of transfer between
mother and fetus
Functions of placenta –
- Exchange of O2 and CO2
- Exchange of nutritive
material & fetal wastes
-Hormone production
- hCG, hPL, estrogen, progesterone
- Barrier function

12. Placental circulation

13. Fetal circulation
List the unique cardiovascuar
structures that ensure effective
delivery of O2 to the vital
centers of the fetus.
1. ------------------------------
2. ------------------------------
3. -------------------------------

14. hCG
Progesterone
hCS
Estriol
delivery
hCG
0 70 140 210 280
Days pregnant
Progesterone
hCS
Estriol
Endocrine changes during pregnancy

15. Chorionic gonadotrophin (h CG)
• Glycoprotein hormone secreted by the
syncytiotrophoblast
• Detectable even before missing menstruation
(sensitive methods)
• Peak ~ 10th week
• Presence in blood / urine – basis of pregnancy test
– detected in blood 6 days after conception
- Detected in urine 14 days after conception
• Prevents degeneration of CL (ensuring continuing
supply of oes/ prog)

16. Placental Lactogen (Chorionic
Somatomammotrophin) [hPL – hCS]
• Secreted by the syncytiotrophoblast
• Structure similar to human GH
• Progressive increase throughout pregnancy
• Responsible for regulating maternal metabolism
• Lipolysis
•  Maternal glucose utilization
•Amount secreted proportionate to the size of
placenta
•Low hCS = placental insufficiency

17. Estrogen
• Source
• Corpus luteum of pregnancy ~ 2 to 3 months
• Feto– placental unit
Functions
Enlargement of uterus
Enlargement of genitalia
Relaxation of pelvic ligaments
• Main type - estriol
Ductal proliferation of breasts

18. Cholesterol
Progesterone
Pregnenolone DHEAS
16 - OHDHEAS
Cortisol,
corticosterone
Estradiol
Estriol
DHEAS
16 - OHDHEAS
Placenta Fetal Adrenal

19. Progesterone -
Corpus luteum of pregnancy ~
2 to 3 months
Placenta
Functions
Development of decidual cells
Prevents uterine contractions
Prepares the breast for lactation

20. Maternal changes in pregnancy
 To facilitate optimal foetal growth and
development (Facilitates maternal and fetal
exchanges of respiratory gases, nutrients and
metabolites)
 To satisfy maternal needs during pregnancy,
delivery and lactation

21. Maternal changes during pregnancy…
• General
– Weight gain
– Increased BMR
• Uterus – Enlarges (hypertrophy and hyperplasia).
Weight increases up to 1 kg. Increased blood supply.
• Vagina and cervix – Increased vascularity and secretions.
Cervix softens.
• Breasts – enlarge to almost double the size(alveolar and ductal
tissue). Nipples and areola enlarged and get pigmented. Dilated
veins become visible.

22. • Body fluid
– ECF retention about 5 L
– Oedema.
• Blood
– Volume increases progressively from 6-8 /52 with
haemodilution
• plasma volume (40-50%)
• red cell mass (20-30%)
Maternal changes during pregnancy…

23. Cardiovascular System
• HR, SV, Cardiac output
• Diastolic blood pressure
(Lowest 2nd trimester and then to non-
pregnant levels)

24. • Respiratory System
– Increased oxygen consumption
– Tidal volume and minute ventilation
– Uterus exerts pressure on diaphragm - more thoracic
muscles used
• Urinary System
– Increased renal size, hydronephrosis and hydroureter
– Increased GFR (serum creatinine low)
– Renal glycosuria.

25. Gastrointestinal System
• Nausea, vomiting – (morning sickness,
hyperemesis gravidarum)
• Alterations in appetite
• Tone, motility ↓ Gastric emptying time
prolonged
• Constipation
• Gastro – oesophageal reflux –
(Heart burn of pregnancy)

26. Venous stasis
• Leg oedema in most pregnant women
(varicose veins in some)
• Why?
– Hormonal changes in pregnancy cause
reduction in venous tone
– Mechanical compression of enlarged uterus
on pelvic veins
– Increased fluid retention
– Decreased colloid osmotic pressure

27. Diagnosis of pregnancy
• How can you diagnose pregnancy?
– History
– Examination
– Investigations