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
