1. L 34. Adaptation to pregnancy, Physiology of parturition & lactation

2. Learning objectives
To discuss the physiological adaptations during normal pregnancy, cardiovascular, respiratory, gastrointestinal, renal and the uterine changes during pregnancy.

3. Learning outcomes
At the end of this lecture students should be abele to;
Describe the physiological adaptations during the normal course of pregnancy
Describe the cardiovascular & respiratory changes during pregnancy
Describe the renal function and electrolyte balance during pregnancy

4. Learning outcomes cont
Gastrointestinal changes during pregnancy
Uterine changes during pregnancy
Describe the physiology of parturition
Describe the role of hormones in functioning mammary gland
Describe the physiology of lactation

5. MATERNAL CHANGES IN PREGNANCY5

6. Duration of pregnancy is 280 days or 40 weeks from the first day of last menstrual period.6

7. The uterus Uterus gains weight from 50g to 1000g.
Length, thickness and volume
Mainly hypertrophy of existing muscle cell and hyperplasia.
There is increase in connective tissue and elastic tissue. 7

8. Mammary Glands Hyperplasia of the ductal and alveolar tissue
Pigmentation of the nipple and the areola 8

9. Changes in blood Blood volume increases by 30% Haematocrit decreases.
aldosterone and estrogens increased in pregnancy
Increased fluid retention by the kidneys
Haematocrit decreases.
Plasma volume increases much more than RBC volume
Increase in fibrinogen level
Increase in ESR. 9

10. Changes in circulatory system
Cardiac output increases to 30 to 40% above normal.
Blood volume increases by 30%.
Blood pressure
Systolic remains same
There is fall in diastolic pressure
Vasodilation (Kinin,Nitric oxide,EDF)
Increase in blood flow to uterus and kidneys 10

11. Respiratory changes Increase in O2 consumption – 20% more than normal
Minute ventilation increases by 50%
Respiratory rate is increased.
Higher levels of progesterone during pregnancy
Increased sensitivity of respiratory centre to CO2
No change in vital capacity. 11

12. CHANGES IN GIT Morning sickness Decrease in motility
Increase in absorption
Increased appetite 12

13. Changes in urinary system
Increased fluid intake and increased load of excretory products
GFR increases as much as 50%.
Reabsorption capacity of renal tubules is increased by 50%
Increased production of hormones by the placenta and adrenal cortex 13

14. Skin Hyperpigmentation
Increased secretion of ACTH and MSH during pregnancy 14

15. CNS
Changes in mood.
Craving for unusual diet. 15

16. Metabolism Increased basal metabolic rate (BMR) Increased secretion
Thyroxin,
Adrenocortical hormones,
Sex hormones 16

17. Increased requirement of iron
Likely to develop iron deficiency without supplementation
Increased requirement of calcium and phosphorus 17

18. OTHER CHANGES Weight gain 10-12 kgs Water retention. Fetus
Uterus , mammary glands
Placenta and amniotic fluid
Increase in blood volume
Fat deposition
Water retention. 18

19. Physiology of PARTURITION19

20. Childbirth
process of giving birth
Also called “labor” 20

21. Increased uterine contractility
Hormonal factors
Increase in estrogen to progesterone ratio
Oxytocin
Fetal hormones
Mechanical factors
Stretch of uterine musculature
Stretch of cervix 21

22. Circulating estrogens
Increases the number of gap junctions between myometrial cells
Production of prostaglandins
Increase in myometrial contractile proteins
Increase in number of oxytocin receptors 22

23. Effect of cortisol Increase in cortisol formation in the fetus.
CRH secretion by the fetal hypothalamus increases
Increased placental production of CRH.
This increases circulating adrenocorticotropic hormone (ACTH) in the fetus 23

24. Positive feedback theory for onset of labour

25. Head descends into the cervix Initiates the cervical stretch
Stretch of cervix
Head descends into the cervix
Initiates the cervical stretch
Increase in contractility of the uterine body
Head descends further
Cycle repeats 25

26. Stretch of cervix and distention of vagina
Uterine contractions
Stretch of cervix and distention of vagina
Afferents from cervix and vagina
positive feedback to the hypothalmus
Oxytocin from posterior pituitary
Formation of Prostaglandins in the decidua 26

27. Two types of positive feedback mechanisms increase uterine contractions during labor:
Stretching of the cervix causes the entire body of the uterus to contract
Cervical stretching also causes the pituitary gland to secrete oxytocin 27

28. Parturition Intermittent contractions of the uterus
Delivery of the fetus
Separation and delivery of Placenta
Shearing effect between walls of uterus and placenta
350 ml of blood loss

29. Physiology of
LACTATION

30. Role of estrogens
Causes the ductal system of the breast to grow and branch.
Stroma of the breast increase in quantity and large quantities of fat are laid in the stroma.
Growth hormone, adrenal glucocoticoids, prolactin & insulin are also needed for ductal growth.

31. Role of progesterone
Acts synergistically with estrogen causes additional growth of the breast lobules,
budding of alveoli
development of secretory characteristics in the cells of the alveoli.

33. Initiation of Lactation-Function of Prolactin
Estrogen and progesterone inhibits secretion of milk.
Prolactin is required for actual secretion of milk.

34. Increase lactogenic effect
Function of prolactin:
prolactin
Promotes the secretion of milk
Estrogen and progesterone
Birth
Decrease [estrogen + progesterone
Increase lactogenic effect
(prolactin)
Increase [milk] in the alveoli of the
Breast – not the ducts!!!!!

35. Galactopoiesis (maintainance of lactation)
Prolactin
GH, Cortisol, PTH, Insulin
Oxytocin

36. Milk Ejection Reflex 36

37. Ejection of Milk: Oxytocin
Milk let down reflex or Suckling reflex
Neuroendocrine reflex
spinal cord
Suckling of breast
Afferent conduction of APs
Contraction of the myoepithelial cells
Ejection of milk
Oxytocin
secretion
hypothalamus
Prolactin
secretion
Increase [milk] in the alveoli of the breast

39. Role of hormones
Estrogen & Progesterone specific effect of both these hormones is to inhibit the actual secretion of milk
Prolactin: stimulates milk production
Oxytocin: stimulates milk release
Human chorionic somatomammotropin :Has lactogenic properties and supports the action of prolactin

40. Effect of lactation on menstrual cycles
Lactation amenorrhea
Nursing stimulates prolactin secretion
Prolactin inhibits GnRH secretion
Action of gonadotropins on ovaries inhibited
“No ovulation”