Parturition And Oactation Flashcards
What is parturition?
Parturitionmeansbirthofthebaby.
• The interactions of maternal &fetal factors regulate birth of the baby
• These include both mechanical & hormonal changes
What are the changes before labor?
- CRH secretion ↑ exponentially
near term - At same time
CRH- BP ↓ causing
What is the significance of CRH?
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
What factors increase Contractility?
• 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
What are the mechanical changes that affect contractility?
• 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
What is the myogenic reflex?
intermittent fetal movements stretch the uterine muscle causing smooth muscle contraction
- twin pregnancy results in early labor
What are the mechanical factors of the myogenic factors?
- 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
What is the relevance of estrogen:progesterone ratio?
• 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
What is the significance of oxytocin?
• Oxytocin
– secretion of oxytocin at labor
– Stretch of cervix oxytocin release
• Thefetus
– Releases oxytocin, cortisol and pg’s
• oxytocin the intensity of uterine contraction
What is the mechanism of action of oxytocin?
Increased IP3 & DAG and therefore Ca2+, causing a contraction
What is the function of oxytocin?
- ↑’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
Summarize placental delivery
- 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
What are the causes of slow or delayed labor?
Cephalopelvic disproportion
Conduction anesthesia
Excessive sedation
Fetal malposition
What stimulates breast development?
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
How is milk production stimulated?
- 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
How does suckling affect milk production?
Mechanoreceptors in the nipple stimulate the hypothalamus
This. Stimulates increased PRF and decreased dopamine inhibition to anterior pituitary
This increases prolactin
What is the impact of prolactin ?
- 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
How is milk ejected?
• 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
How long does it take for milk ejection?
- 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
How does sychology help with milk ejection?
Also psycho sensory input such as hearing a baby cry or performing baby care can cause ejection of milk
