ChildbirthAnatomy and Physiology of Childbirth
Normal pregnancy, childbirth, and lactation are physiologic events in the lives of healthy women. Physiologic childbirth is the normal labor and delivery of a full term baby and the placenta. Childbirth is divided into three stages. Three stages of childbirth have phases in each stage. The first stage of labor begins with regular, rhythmic contractions of the uterus that dilate and efface the cervix The first stage of labor is divided into latent, active, hard, and transition phases. The first stage of labor ends when the cervix is 10 centimetres dilated and 100% effaced. The second stage of labor is divided into two phases: descent (pushing preborn baby down the birth canal) and delivery (expulsion). The third stage of labor includes the separation and delivery of the placenta (a fetal organ). The fourth stage is a period of observation, adjustments, falling- in-love with baby, and establishing breastfeeding. Well-nourished mothers may have shorter labors compared to poorly nourished pregnant mothers. Before Labor Begins Lightening “Lightening” and “dropping” mean the same thing: the fetus descends into the maternal pelvis. Lightening often happens 2 to 6 weeks before labor for first time mothers and is not a necessary indication that labor is about to happen. First time moms usually experience lightening 2 to 6 weeks before labor starts. Women who have already given birth one or more times may not experience “lightening” until labor actually starts. Full term More Frequent Urination The bladder has less room especially after the baby has “dropped.” Frequent urination is common in the last days and weeks of pregnancy. Braxton-Hicks Contractions Braxton-Hicks (tuning up) contractions become more frequent. Noticed as tightening around the hips, your uterus will get hard and stand up away from your body. Generally painless, these contractions work to slightly shorten and open the cervix. Tuning Up Contractions “False Labor" False labor is the process of your body tuning up for the “real” thing. Tuning up contractions Soften Shorten Start to open the cervix. These “false labor” contractions prepare you and your baby for birthing. Cervical changes A cervix “ripe” for labor is soft, short, and slightly open. True labor True labor is a process when your uterus contracts in a coordinated manner over a sufficient length of time in a pattern that does not stop when you change activities ~ to bring about the spontaneous birth of your baby. First stage of labor During the first stage of labor the uterus undergoes formation of the upper and lower segments. The upper and lower segments work together during labor. The upper segment contracts and thickens. The lower segment contracts slightly and distends. The lower segment includes the cervix. The cervix dilates and effaces. Changes in the Cervix The cervix is like the neck of a turtleneck shirt. The uterus is like the body of the shirt. The cervix is the "neck" of the uterus. Before you put on a turtleneck shirt, if you hold it upside down by the bottom, the neck of the shirt is long. The opening of the neck of the shirt is slightly open. Pull your turtleneck shirt over your head. The neck shortens, thins, and opens so your head will pass through. Contraction and retraction of the uterine muscles cause the cervix to efface, thin, and dilate, much like a turtleneck! Formation of bag of waters The lower segment distends. The chorion (outer membrane of the amniotic sac) detaches from the uterus. Chorion bulges slightly in front of the fetal head. Cutting off waters in front of engaged head. Creates a cushion between fetal head and cervix. Acts as an aid to help dilate the cervix. Effacement of the cervix Effacement is shortening of the cervix. Muscle fibers surrounding the internal os (opening) are drawn upward. Dilation Dilation occurs with upward traction from retracted muscle fibers of the upper segment of the uterus. First time mothers may be 1 or 2 centimeters dilated at onset of labor. The cervix effaces first then dilates. Women who've given birth one or more times may be dilated 4 cm or more at onset of labor. Contraction/Retraction of Uterine Muscle The uterus is the strongest muscle in the human body! A contraction is the shortening and thickening of muscle fiber. Contractions begin at the top of the uterus, called the fundus. Contractions spread downward. Contractions diminish in intensity when reaching the lower uterine segment. Retraction is retention of some of the contraction. The uterine muscle contracts, relaxes, and retains some of the contraction. The upper segment of the uterus .progressively becomes shorter with less space inside as muscles retract more. The 2nd Stage of Labor The second stage of labor begins as soon as the cervix is fully effaced and fully dilated to 10 centimeters and ends with complete birth of the baby's body. Two phases of second stage Descent Delivery Descent: Moving that baby down Contractions stronger and after a brief lull, may be more frequent. The cervix is 10 centimeters dilated and fully effaced (drawn up making the inside of the uterus and the vagina one continuous "canal." The abdominal muscles and the diaphragm are active in pushing. Pelvic Floor The pelvic floor is made up mostly of muscular tissue. 6 pairs of muscles and acts like a sling or hammock by mode of attachment. The pelvic floor internally constitutes the base of the abdominal cavity. Organs anchored in pelvic floor include: Cervix Upper vagina Bladder Rectum All organs are surrounded by connective tissue. All organs are sustained by muscle and strong fascia attachments. The pelvic floor is displaced as the fetus moves down the birth canal. Delivery Preborn baby (fetus) moves through the maternal pelvis, classically head down, chin to chest. The fetal head turns to one side (right or left) to move through the maternal pelvis. The fetal head turns again at the maternal pubic bone. Pubic bone keeps chin down to chest (head flexed). Top of head shows at the vulva Head recedes between contractions --two steps forward, one backward. Membranes Rupture Can rupture at any time. Sometimes membranes are ruptured speed labor during first stage. Classically happens during second stage. Intact membranes help dilate the cervix. Intact membranes help protect preborn baby’s head. Use of an internal fetal heart monitor requires rupture of the membranes. Amniotomy is performed before electrode is inserted into baby’s scalp. Crowning The perineum is thinned. The largest diameter of the head is born and no longer recedes between contractions. The head is born by extension of the neck as the face "sweeps" across the perineum through the chin lifting up off the chest. Episiotomy Crowning of the head is the classic time an episiotomy is typically done. Some doctors or midwives will work with a mom delivering the head and shoulders to avoid episiotomy: When to push How long to push An episiotomy may be a spot judgment of doctor and mother. Some reasons for an episiotomy are: Get baby out quickly Physically and emotional comfort for mom. Birth of Shoulders The top (anterior) shoulder is born. The bottom (posterior) shoulder is born. Push your baby’s body out. Your baby may be lifted to your belly. Third Stage of Labor The third stage of labor is the separation and expulsion of the placenta. The third stage of labor begins with the complete birth of baby and ends with the complete birth of the placenta. Contractions may slow down. Contractions shrink the uterine cavity. Contractions make uterus smaller until the placenta separates from the uterine wall. Blood from the placenta flows to the baby. +40 percent of baby’s total blood volume is in the placenta. Blood stops flowing from baby to placenta. Less blood in placenta makes placenta shrink and separate from implantation site in uterus. Placenta separates from the uterine wall. Placenta is pushed out and expelled. Placental Examination Maternal side of human placenta The placenta is examined on the maternal side for cotyledons that fit together like pieces of a puzzle. Membranes are examined for wholeness (and the hole in the "bag"). Any pieces of cotyledon or membranes, still inside the uterus, may cause bleeding. The placenta is examined for its shape. Fetal side of the human placenta The placenta is examined for any infarcts (white spots). Fourth Stage of Labor The fourth stage of labor is a time of observation of mother and newborn for complications. Establishing Breastfeeding. Usually within the first hour or so after birth, a newborn will latch on and suckle. Some babies take a little longer. Discovery and getting to know your baby. Falling-in-love with baby. |
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"Childbirth is a normal event in the lives of healthy women."
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