Childbirth known parturition, usually occurs within 15days of the calculated due date (280 days from LMP). The parturition means aprocess of delivering the baby and placenta from the uterus to the vagina tothe outside world called labour and delivery. There are series of events thatpropel the infant from the uterus, are referred to collectively as stages oflabour. The precise trigger for labour is not clear because some women maybeoverdue more likely if it is a first baby.Human chorionic gonadotropin (HCG): stimulates the productionof oestrogen and progesterone within the ovary, production of this hormonediminishes once the placenta is mature enough to take over oestrogen andprogesterone production which are secret by the corpus luteum. Oestrogens help regulate levels of progesterone andprepare the uterus for the baby, progesterone contains high levels of hormoneswhich prevent uterine contractions while the baby is still developing andtherefore decrease, for labour to occur.
By preventing contractions of theuterus. (Braxton hick’s contractions), painful contractions accompanied bythinning and the opening of the cervix up to 4cm, lasting 35-45 seconds andoccurs during the latent phase of the first stage of labour, that may last fora very long time, especially for first time mums and the length of this phasecan range from six hours to two-three days. As oestrogen begins to stimulate uterine contractions,the pituitary gland releases hormone from the mother called oxytocin hormonethat stimulates contractions of the uterus during achieving childbirth andlabour that stimulates the placenta and produce prostaglandins, tissue hormonethat helps start labour and used to induced labour.
These contribute to thedecrease of progesterone level, initiating labour along with the relaxinhormone which relaxes the muscle of the cervix, in the final phase of the firststage of labour is transition stage, causing the cervix to dilate from about 4centimetres to 7 centimetres (10 centimetres, making room for the baby to passthrough), indicating fully dilatedcervix, usually 6-12 hours or longer. Leading to active labour in the firststage of labour. Which leads to the expulsion of the foetus from the mother’suterus in the second stage of labour, this stage takes as long as 2 hours, it istypically 50 minutes in a first birth and around 20 minutes in subsequentbirths.However, the final stretch of growth stretches the uterusto its limits which put a physical stress, on both the baby and the uterus,causing the releases of a stress hormone called corticotropin-releasing hormone(CRH) and cortisol, increase during the last few days and weeks of gestation.
When it rises, it triggers a rise in the steroid hormone called estriol a formof oestrogen that is major during childbirth. which inhibits the synthesis ofprogesterone by the placenta and prepares the smooth muscles of the uterus forlabour, leading to the third stage of labour in the delivery of the baby endingwith the delivery of the placenta and the empty bag of waters that are attachedto the placenta (membranes). A structure or tissue, such as the chorion, amnionsac that comes away as the Uterus (womb) contracts down after birth. This isthe shortest stage and usually accomplished 15 minutes after the birth of thebaby.5.2 EXPLAIN THE CHANGES IN THE FOETALCIRCULATION AT BIRTHFoetal circulation and changes also occur before birth,when the foetus is not capable of respiratory function and therefore relies onthe maternal circulation to carry out gas, nutrient and waste exchange. Thefoetal and maternal blood never mix, instead, the interface at the placentabecause nutrient and oxygen are passed over by diffusion only and if themothers and foetus blood mixed, it could be deadly for both of them. As aresult, the liver and the lungs are non-functional, and a series of shuntsexist in the foetal circulation so that these organs are almost completelyby-passed.
After birth, during the first stage of labour bloodoccurs in the Ductus venosus a trumpet-shaped vessel, provides a means foroxygenated umbilical vein blood to bypass the sinusoids of the liver. Theamount of blood passing through the vessel seems to be regulated by a sphinctermechanism. For example, to prevent an excessive venous return to the right sideof the heart during uterine contractions, there is a relative contraction ofthe ductus venosus.This flows into the right atrium and is directed towardsthe foramen ovale, a small hole located in the septum, which is the wallbetween the two upper chambers of the heart (atria) with an anatomic adaptation in the foetus thatallow oxygenated blood coming from the umbilical vein through the inferior venacava to bypass the pulmonary circulation. It is mixed with a small volume ofblood returning from the non-functional lungs through the pulmonary veins andpasses into the systemic circulation thereby bypassing the lungs.
The followingstructures pass through foramen ovale: Mandibular nerve. The motor root of thetrigeminal nerve. Accessory meningeal artery (small meningeal or periduralbranch, sometimes derived from the middle meningeal artery). While the ductusarteriosus, also called the ductus Botalli, is a temporary blood vesselconnecting the pulmonary artery (the main heart vessel leading to the lungs) tothe proximal descending aorta (the main blood vessel of the body). It allowsmost of the blood from the right ventricle to go around the foetus’sfluid-filled non-functioning lungs before birth. Most of the blood in the aortais then returned to the placenta for oxygenation through the umbilicalarteries. Blood is emptied into the aorta after the artery head has branchedoff through ensuring that the brain receives well-oxygenated blood.Changes at and after birth occur when the pressurechanges due to inflation of the lungs and the increased flow through thepulmonary arteries close the foramen ovale and the ductus arteriosus muscularwall contracts and close and is effectively obliterated within 2 months,becoming the ligamentum arteriosum.
The ductus venosus becomes the ligamentumvenosum (passing around the caudate lobe of the liver), and the intra-abdominalumbilical vein becomes the ligamentum teres.The umbilical arteries becomeobliterated and form the medial umbilical ligaments (not to be confused withthe median umbilical ligament which is the obliterated remains of the urachus).6.1,Explain the hormonal control of lactation.Lactation is under endocrine control. The two mainhormones involved are prolactin and oxytocin.
Prolactin is the hormone that stimulates mammarygland development and stimulates milk production called lactogenesis. During pregnancy, the body prepares for lactation bystimulating the growth and development of branching lactiferous ducts andalveoli lined with milk-secreting lactocytes.By the end of the 6 month the mammary glandsare fully developed, and gland cells begin to produce a secretion known ascolostrum.
These functions are attributable tothe actions of several hormones, including prolactin. Following thefirst two or three days of childbirth, mammary gland secretion of breast milk suckling triggers and Stimulated tactilereceptors stimulate the release of oxytocin from the posterior lobe of thepituitary gland. Oxytocin causes contraction of the myoepithelial cells in thewalls of the lactiferous ducts to squeeze milkfrom alveoli and milk is ejected. The delivery of the placenta and the resultingdramatic reduction in progesterone, oestrogen, and human placental lactogenlevels stimulate milk production. The milk produced in the firstpostpartum days, contains more protein and less fat than breast milk, andmany of the proteins are antibodies that may help the infant fight offinfections until its own immune system develops.Mature milk changes from the beginning to the end of a feeding, whereas,Foremilk quenches the infant’s thirst, whereas hind milk satisfies the infant’sappetite.6.
2,Explain the difference between milk and colostrum.The colostrum isyellow in colour and thick and the mature milk is white in colour and thin. Whereas,breast milk is roughly divided into 2 stages. It first comes out in about aweek after childbirth is called colostrum and one after that is called maturemilk. While colostrum isyellow in colour and thick. At the beginning, it comes out just like oozingfrom the nipples.
As the baby suckle, the quantity get increased. And after7-10days, the colour of breast milk becomes white in colour and thin. Thequantity of it increases gradually and the breasts come to be bloated, so it ishappening that breast milk comes out from nipples a lot.