Parturition And Oactation

Question 1

What is parturition?

Answer 1

Parturitionmeansbirthofthebaby.
• The interactions of maternal &fetal factors regulate birth of the baby
• These include both mechanical & hormonal changes

Question 2

What are the changes before labor?

Answer 2

• CRH secretion ↑ exponentially
  near term
• At same time
  CRH- BP ↓ causing

Question 3

What is the significance of CRH?

Answer 3

In fetus the CRH targets not only the pituitary gland but fetal zone of the adrenal
gland to preferentially secretes DHEAS over cortisol

• This results in ↑ estrogen to progesterone ratio prior to parturition

There. Is increased estrogen to progesterone ratio just prior to birth

Question 4

What factors increase Contractility?

Answer 4

• Uterusisquiescentduringpregnancyas progesterone inhibits smooth muscle contraction thereby inhibits fetal expulsion
• Estrogens
– ↑s the no of gap junctions in the myometrium

– ­increases pg production by placenta

– ­increases no. of oxytocin receptors in myometrium

– estrogen ↑s uterine excitability

Question 5

What are the mechanical changes that affect contractility?

Answer 5

• Stretch of uterine smooth muscle leads to contraction
- may stimulate myogenic reflex

• Stretch of the cervix
– May stimulate neurogenic reflex which stimulates release of oxytocin

Question 6

What is the myogenic reflex?

Answer 6

intermittent fetal movements stretch the uterine muscle causing smooth muscle contraction

• twin pregnancy results in early labor

Question 7

What are the mechanical factors of the myogenic factors?

Answer 7

• There is coordinated contraction of uterus
• Just prior to labor uterus develops into functionally 2 distinct segments
• The upper segment is thicker & more muscular than the lower region
• Contractions occur from upper to lower segment
• Placenta is usually in the upper segment
• This facilitates the delivery of fetuses
• Lower segment is relatively thin & muscular & fuses with vagina
• Unification is observed as. dilation of cervical external os from 1-2cm to 10cm
• Placenta previa is implantation of placenta in the lower segment
• Results in delivery of placenta before fetus & is life threatening for fetus as it comprises blood flow

Question 8

What is the relevance of estrogen:progesterone ratio?

Answer 8

• The estrogen:progesterone ratio increases closer to birth

• There is a rise in prostaglandin secretion
• Pg F2 & E2 are potent stimulators of contractility, & cause significant ripening & dilation of cervix

Question 9

What is the significance of oxytocin?

Answer 9

• Oxytocin
– ­ secretion of oxytocin at labor
– Stretch of cervix ­ oxytocin release

• Thefetus
– Releases oxytocin, cortisol and pg’s

• ­oxytocin ­the intensity of uterine contraction

Question 10

What is the mechanism of action of oxytocin?

Answer 10

Increased IP3 & DAG and therefore Ca2+, causing a contraction

Question 11

What is the function of oxytocin?

Answer 11

• ↑’s both amplitude & frequency of contraction
• Frequency of contractions. is 2-4strong contractions every 10 minutes at the onset of labor
• Rhythmic contractions allows fetal blood to be oxygenated adequately
• Synthetic oxytocin(Pitocin) is sometimes used to augment or induce labor

Question 12

Summarize placental delivery

Answer 12

• Uterus shrinks after the delivery of the baby
• This causes shearing effect between the walls of uterus
  & placenta separating it
• this causes bleeding but is limited by continued uterine contractions which cause vasoconstriction & vasospasm

Question 13

What are the causes of slow or delayed labor?

Answer 13

Cephalopelvic disproportion

Conduction anesthesia

Excessive sedation

Fetal malposition

Question 14

What stimulates breast development?

Answer 14

DuringPregnancy
– GH, PRL, cortisol and insulin help develop the ductal system
– Estrogen is the major promoter

• Progesterone required to help with final growth of alveovli & its ability to secrete milk

Question 15

How is milk production stimulated?

Answer 15

• increased levels of estrogens & progestins inhibit milk production during pregnancy
• Prolactin levels are high during pregnancy
• GH, cortisol, PTH, insulin inhibit the mammary gland, it’s required to supply ingredients AA, FFA, glucose & Ca2+

Post pregnancy estrogens and progestins levels decrease allowing lactogenic action of prolactin

Question 16

How does suckling affect milk production?

Answer 16

Mechanoreceptors in the nipple stimulate the hypothalamus

This. Stimulates increased PRF and decreased dopamine inhibition to anterior pituitary

This increases prolactin

Question 17

What is the impact of prolactin ?

Answer 17

• Initially↑levels of prolactin will suppress the GnRH pituitary access in the mother causing anovulatory cycles in females breast feeding the babies
• However this effect is transient after a few months the ovarian cycle is restored even though nursing of baby continues

Question 18

How is milk ejected?

Answer 18

• Milk is continuously produced by the alveoli but does not flow into the ductal system so it does not leak
• It must be ejected into the ducts before the baby can obtain it
• This is achieved by bothneurogenic & hormonal response
– Via oxytocin
– Contraction of myoepithelial cells of the alveoli

Question 19

How long does it take for milk ejection?

Answer 19

• Takes ~1min of suckling for milk to be ejected
• Initially colostrum is secreted for a day or 2
• Colostrum is devoid of fat
• Over next 2 to 10. days breasts secrete copious quantities of milk
• Besides providing nutrients to the baby it contains antibodies that serves protective function

Question 20

How does sychology help with milk ejection?

Answer 20

Also psycho sensory input such as hearing a baby cry or performing baby care can cause ejection of milk