HUB228 2024 Lecture 24 PDF

Lecture 24 Labor and Lactation B Nursing II HUB228 2024 Dept. Medical Biosciences University of the Western Cape  Labor Labor = series of events that expel the fetus from the uterus Parturition or birth = forcible expulsion of the fetus Labor consist...

Lecture 24 Labor and Lactation B Nursing II HUB228 2024 Dept. Medical Biosciences University of the Western Cape  Labor Labor = series of events that expel the fetus from the uterus Parturition or birth = forcible expulsion of the fetus Labor consists of three stages: 1) Dilation stage 2) Expulsion stage 3) Placental stage but before labor is triggered, a number of chemical events are first initiated…  Initiation of labor 1) Estrogen levels peak during the last weeks of pregnancy, leading to: - increased expression of oxytocin receptors on myometrial cells (smooth muscle cells) of uterus - suppression of inhibitory influence of progesterone (the levels of which peak before parturition, inhibiting contraction of myometrial cells) → myometrium becomes increasingly irritable → weak, irregular uterine contractions called Braxton Hicks contractions (false labor pains) occur 2) Oxytocin and prostaglandins convert false labor into true labor: - certain fetal cells begin to produce oxytocin, which causes the placenta to release prostaglandins → both hormones produce powerful, frequent uterine contractions (myometrium “primed” to respond to oxytocin because of increased receptor expression caused by estrogen peak)  Initiation of labor 3) A positive–feedback mechanism is established: - increasing emotional & physical stresses stimulate mother’s hypothalamus to release more oxytocin from her posterior pituitary gland - oxytocin causes further contraction, which causes further oxytocin release, which causes further contraction & so on… → rhythmic, expulsive uterine contractions are triggered 4) Fetal fibronectin changes to a lubricant: - the fetal & maternal tissues are bound together throughout pregnancy by a natural adhesive protein called fetal fibronectin, that changes to a lubricant just before true labor begins → expulsive uterine contractions are further aided parturition can be “accelerated” by administering drugs like oxytocin premature birth can be prevented by administering drugs that interfere with oxytocin or prostaglandins (e.g. ibuprofen, an anti- prostaglandin drug) Initiation of labor  Labor stage 1: Dilation dilation stage = time from onset of true labor until cervix is fully dilated by baby’s head (about 10 cm in diameter) - at first, weak & regular contractions (10-30 sec, 15-30 min apart) begin in upper uterine segment & move down toward vagina - later, vigorous & rapid contractions begin in lower uterine segment as well Head position changes: early on, - cervix thins & dilates with each widest head dimension is along left- contraction as infants head is right axis, later on, in the forced against it - amnion eventually ruptures, anteroposterior axis releasing amniotic fluid, called “breaking the water” - this is the longest stage & lasts 6-12 hrs or more  Labor stage 2: Expulsion expulsion stage = lasts from full dilation of the cervix to delivery/childbirth - strong uterine contractions occur every 2-3 min & each one lasting about 1 min - mothers undergoing labor without local anesthesia feel urge to contract their abdominal muscles, which assists with uterine contractions - crowning occurs when the widest diameter of the baby’s head distends the vulva - an episiotomy (a cut through the clinical perineum) can be performed to widen the vaginal The vertex (head first) presentation orifice allows baby to be suctioned free of - this stage lasts about 50 min mucous & to breath before but can take up to 2 hrs completely out of the vagina.  Labor stage 3: Placental the placental stage, or the delivery of the placenta is accomplished within 30 min - 1hr after delivery of the infant continued strong uterine contractions cause the placenta to detach from the endometrium & it can then be easily removed with a gentle tug on the umbilical cord the ejected placenta & its attached fetal membranes are collectively called the afterbirth it is very important that all placental fragments are removed to prevent postpartum bleeding (continued uterine bleeding after birth)  Labor complications the central tendon of the perineum helps support the uterus & vagina tearing or stretching of this tendon during childbirth can cause a prolapsed uterus: - the uterus may “sink” so that the uterine cervix moves down into the vagina or - the uterine cervix moves down near the vaginal orifice or - the uterine cervix may protrude through the vaginal orifice www.mum.org  Labor complications dystocia = prolonged & difficult birth - possibly due to deformed/malelike pelvis of mother - can cause extreme maternal fatigue - can cause fetal brain damage, resulting in cerebral palsy or epilepsy - an episiotomy is sometimes performed to prevent this - a cesarean (C-) section is often performed to prevent this  Labor complications Cesarean-section (C- section) = delivery of an infant through an incision made through the abdominal & uterine walls www.health.enotes.com www.healthofchildren.com www.pennhealth.com  Labor complications in breeched and other nonvertex presentations, delivery is much more difficult & often requires the use of forceps if the baby is breech, their bottom is the part of their body closest to the birth canal a) complete breech is when both of the baby's knees are bent and his feet and bottom are closest to the birth canal b) incomplete breech is when one of the baby's knees is bent and his foot and bottom are closest to the birth canal c) frank breech is when the baby's legs are folded flat up against his head and his bottom is closest to the birth canal Labor complications www.moondragon.org  Lactation lactation = production of milk by the mother’s mammary glands the mammary glands have fully developed by the end of the 6th month of pregnancy Why does a pregnant woman’s breasts get bigger? - the high concentration and continuous presence of estrogens & progesterone cause expansion of the duct system & secretory units of the mammary glands - additional adipose tissue is deposited  Lactation for the first few days after birth, Non-lactating the glands first produce colostrum, a yellowish secretion that contains - far more vitamin A, minerals & proteins than true breast milk o many of the proteins are antibiotics that ward off infant infections until the infant’s own immune system is functional - far less lactose & fat than true breast milk Lactating after the first couple of days, glands convert to milk production - milk contains a mixture of water, proteins, amino acids, lipids, sugars, salts & large quantities of lysozymes (enzymes with antibiotic properties) cellbio.utmb.edu  Lactation prolactin, which is produced by the anterior pituitary gland, is the hormone responsible for milk production: - high levels of estrogen & progesterone during pregnancy inhibit the effect of prolactin on the mammary glands & therefore prevent milk production - after parturition, however, estrogen & progesterone (& prolactin) levels decrease & so prolactin stimulates milk production - despite decreased basal levels of High levels of prolactin during lactation prolactin, suckling stimulates the secretion of prolactin-releasing suppresses the release of FSH & LH. hormone causing a surge in Therefore, after parturition menstruation and prolactin release (up to 20 fold) ovulation do not start immediately again, but this period of lactational amenorrhea is variable (3 months – 3 years).  Lactation: the milk let-down reflex stored mammary gland secretions are released as a result of a neuro-endocrinal reflex response: - mechanical stimulation of the nipple produces nerve impulses that cause the release of oxytocin from the posterior pituitary gland - oxytocin then stimulates the myoepithelial cells surrounding the alveoli to contract - milk is then released from the breasts in a process called milk let-down or milk ejection the milk let-down reflex continues to function for 1-2 yrs after birth  Lactation Advantages of breast milk: - its fats & irons are better absorbed & its amino acids are more efficiently metabolized than those of cows milk - it contains many beneficial chemicals that protect the infant against life- threatening infections - it contains anti-inflammatory agents and substances that prevent ulcers - its natural laxative effect helps cleans the bowels of meconium (tarry, green- black paste containing sloughed-off epithelial cells, bile & other substances such as bilirubin) helping to prevent physiological jaundice - encourages bacteria (source of vitamin K and some B vitamins) to colonize the large intestine HIV can be transmitted from mother to child via breast milk: – HIV patients are therefore advised not to breast-feed but rather to use formula and bottle-feeding  Check your understanding A labor complication involving prolonged and difficult birth is referred to as ____________, a) false labor b) a complete breech c) a frank breech d) dystocia e) an episiotomy  Check your understanding A labor complication involving prolonged and difficult birth is referred to as ____________, a) false labor b) a complete breech c) a frank breech d) dystocia e) an episiotomy  Check list Make sure you can define the following terms: labor and parturition Braxton Hicks contractions false vs true labor fetal fobronectin vertex and breech presentation crowning afterbirth episiotomy, dystocia, cesarean (C-) section lactation colostrum meconium and physiological jaundice lactational amenorrhea  Check list Make sure you can answer the following questions: 1. Describe the four chemical events that precede labor. (10) 2. Describe the hormonal induction of labor. (6) 3. Name the three stages of labor. (3) 4. Name the first stage of labor (1) and briefly describe the events that characterize this stage (5). 5. Name the second stage of labor (1) and briefly describe the events that characterize this stage (5). 6. Name the third stage of labor (1) and briefly describe the events that characterize this stage (4). 7. Name the different mammary gland secretions (2) and distinguish between their contents (6). 8. Name the hormone responsible for milk production (1) and describe how its secretion levels are controlled during gestation and lactation (5). 9. Describe the milk let-down reflex (5). 10. Discuss the advantages of breast milk (5).