Flashcards in Parturition/Lactation Deck (41):
What are the three phases of parturition?
1- initiation of labor 2- delivery of fetus and placenta, 3- uterine contraction to revert back to pregravid size
What are the major factors of parturition?
estradiol, PGE2 and PGF2a, and Oxytocin
What does PGE2 do in non-pregnant women? pregnant?
relaxes myometrium; uterus contractions (both PGF2a and PGE2
What does estradiol do during parturition?
induces PGE2 and PGF2a production in fetal membrane and myometrium and oxytocin receptors in the myometrium
What do PGs do during parturition?
initiate uterine contractions, activates stretch receptors in cervixmyometrium (stimulus from fetal head, huge # of stretch and pain fibers in both)
What does oxytocin do?
maintains uterine contractions and stimulates PG production
What is the mechanism for the onset of labor?
P decreases myometrial contraction during pregnancy, reduced calmoudulin and placental PGE2 synthesis and degradation of PG via PG dehydrogenase; increase E2 near term override P inhibition and stimulate PGE2/PGF2a synth-> uterine contraction and activate cervical collagenase-> soften cervix; 2d half preg. uterus undergoes periodic slow and weak rhythmic contractions (Braxton-Hicks); rate and intensity increases til 2nd phase
What causes labor pain?
massive contractions excite uterine pain fibers
how does the fetal head assist in onset of labor?
stretches soft cervix-> initiation of neurogenic stimulus to hypothalamus causing oxytocin release-> stimulates placental synth. of contractions->further stretching of cervix-> positive neurogenic feedback loop to oxytocin secretion-> stringer contractions-> leads to fetal exit->10-45 min after delivery ->expulsion of placenta (350mL blood loss)
How does estradiol work in mammary gland development?
induces lactotrope hyperplasia, oxytocin receptors in alveolar and ductal myoepithelial cells, stimulates prolactin synthesis; also reduces dopamine synth and D2 receptor level in lactotropes leading to disinhibition of prolactin synth and secretion
What hormones are necessary for ductal development?
E2 + GH + prolactin
What hormones are needed for lobulo-alveolar development?
P + E2 + Prolactin + GH + Insulin + IGF-I + Thyroxine + Cortisol
What role does dopamine play in mammary gland development for lactation?
D from arcuate nucleus fo hypothalamus via D2R activates Gai which inhibits andenylate cyclase activity; Prolactin synth decreases due to low cAMP, secretion decreases due to low intracellular [Ca]
What role does prolactin play in galactopoeisis?
stimulates synth of major milk proteins (B-casein 60% and whey 40%-including a-lactoalbumin, b-lactoglobulin, Ig, albumin, and UDP-galactosyl transferase; induces E and prolactin receptors in mammary gland epithelial cells
What else is required besides prolactin for galactoporeisis?
cortisol at physiological levels for expression of transcription factors for milk protein synth,
Why does galactopoiesis only occur late in gestation even though P is available?
P antagonizes alveolar cells prolactin receptor by inhibiting up regulation of prolactin receptor, reducing estrogen binding, competing for binding of glucocorticoid receptor; high levels of E2 interferes with prolactin binding to its receptors-> inhibits terminal differentiation of alveolar epithelial cells
When does breast engorgement and milk secretion occur?
2-4 days postpartum when steroids are sufficiently cleared from maternal blood
What stimulus is needed to induce Milk-let-down reflex?
suckling-induced sensory signals from nipple and areola reach SON and PVN-> release of oxytocin-> contractions of myoepithelial cells surrounding ducts and alveoli-> milk flow through the duct (also needed for secretion of prolactin during lactation)
What is first milk?
colostrum, high amounts of B-carotene, proteins, IgA, lactoferrin and relatively lower amounts of lactose
What is the composition of mature human milk?
Protein 0.8-0.9%, Carb 6.8-7.2%, Fat 3-5%, Mineral 0.2% and water
What are the proteins in mature human milk?
B-casein, a-lactalbumin, lactoferrin, IgA, lysozyme, and albumin
What are the carbs in mature human milk?
lactose but 30 or more oligosaccharides also present
What are the fats in mature human milk?
Triglyc; most common are aplmitic and oleic
What are the minerals in mature human milk?
Na, K, Ca, Cl, Mg, P, Fe, Cu, and Zn
What does lactoferrin do for the baby?
inhibits growth of iron dependent bacteria in GI tract (coliforms and yeasts requiring iron too)
What does secretory IgA do for infant?
protect infant from viruses and B, specifically those that baby, mom and family are exposed to; helps protect against E coli and possibly allergies; other immunoglobins IgG and IgM help protect against B and viral infections
What does lysozyme do for the baby?
protects against E. coli and salmonella; promotes growth of healthy intestinal flora and has anti-inflammatory functions
What does bifidus factor do for the baby?
supports growth of lactobaccilus-> beneficial B that protects baby against harmful B by creating acidic environment
What specifically does suckling induced prolactin do? Suckling induced oxytocin?
stimulates milk synthesis; let down of milk
What causes galactopoeisis to cease?
withdrawal of breastfeeding; maintained as long as stimulation of breast is continued
What are the advantages of breastfeeding for the infant?
species specificity, optimal growth of infant, breast milk perfectly matches infants daily requirement, long chain FA development; antimicrobial factors protect against illness, prevention of acute illness (diarrhea, necrotizing enterocollitis, meningitis, UTI, and respiratory illness- pneumonia, bronchitis, otitis), protect against chronic illness- juvenile diabetes mellitus and ulcerative colitis; protection against allergic disease, improved cognitive development, reduced risk SIDS, ready source of comfort and security
What are the maternal advantages of breastfeeding?
more rapid uterine involution, early return of pre-pregnancy weight, prolonged post-partum anovulation (PRL inhibits GnRH), conectption 1st 6 mo, less menstrual blood loss, cost saving, enhance interaction, convenience and ease of feeding, and reduced risk of : post menopausal hip Fx, pre-menopausal breast cancer, ovarian cancer
What are infant contraindications to breast feeding?
prematurity, IUGR and < 6lbs, multiple births, cardiac disease, respiratory distress, infection esp mouth, lactose intolerance, neurologic problem, neonatal jaundice, latch-on problems, reluctant nurses, dysfunctional suckling, and oral anatomic abnormality: cleft lip/palate, micrognathia
What are maternal contraindications to breast feeding?
variation in breast appearance (hypoplastic, tubular), excessive or unrelieved postpartum breast engorgement, previous breast surgery or absess, previous problem with milk synthesis, severe or chronic sore nipples: mechanical trauma, yeast or bacterial infection, sensitive/dry skin and consequent skin crack, flat or inverted nipples affecting infant latch on/milk removal, perinatal complication (high bp/infection), underlying systemic illness (cystic fibrosis, diabetes, heart disease), failure of milk production in first 7 days may be sign of Sheehans, or extremes in maternal age (38)
What is galactorrhea?
secretion of milky fluid from breast at times other than pregnancy
Where can the problem exist in galactorrhea?
activation of afferent neuroendocrine limb, decreased dopamine release or function, prolactinomas of anterior pituitary or ectopi PRL production, elevated TRH during hypothyroidism and chronic renal failure
What are examples of activation of afferent neuroendocrine limb in galactorrhea?
stimulation by suckling, excessive manual stimulation, heroes zoster of thoracic nerves, spinal cord lesions and breast surgery
What are examples of decreased dopamine release or function causing galactorrhea?
drugs like phenothiazines, morphine, amphetamines, estrogens can interfere with dopamine metabolism
What are examples of prolactinemias of anterior pituitary or ectopic PRL production in galactorrhea?
tumors- renal, liver and uterine fibroids
What are examples of elevated TRH causing galactorrhea?
in hypothyroid pts sometimes exhibit hyperprolactinemia with remarkable pituitary enlargement due to thryotrope hyperplasia; thyroid replacement with reduction in pituitary enlargement and normalization of PRL