OB Exam 2 Study Guide! PDF

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Comprehensive notes on the material covered for Dr. Newman's Exam 2. These notes come directly from the textbook. ...

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OB Exam 2 Labor and Childbirth Initiation of Labor pg. 456  It is believed that labor is influenced by: uterine stretch from the fetus and amniotic fluid volume, progesterone withdrawal to estrogen dominance, increase oxytocin sensitivity, and increased release of prostaglandins  Estrogen to progesterone ratio o During the last trimester estrogen increases and progesterone decreases  The number of oxytocin receptors in the uterus increases at the end of pregnancy  Increased levels of estrogen also lead to increased sensitivity to oxytocin  With increasing oxytocin levels in the maternal blood along with increasing fetal cortisol levels that synthesize prostaglandins, uterine concentrations are initiated  Oxytocin also aids in stimulating prostaglandin synthesis  Prostaglandins lead to additional contractions, cervical softening, gap junction induction, and myometrial sensitization leading to progressive cervical dilation  Uterine contractions have two main functions: dilate the cervix and to push the fetus through the birth canal Signs of Approaching Labor pg. 456  Lightening occurs when the fetal presenting part begins to descend into the true pelvis o The uterus lowers and moves into a more anterior position o The woman will usually notice her breathing becomes much easier and there is decreased gastric reflux o She may complain of increased pelvic pressure, leg cramping, dependent edema in the lower legs, low back discomfort, increase in vaginal discharge and urination o In primiparas, lightening can occur 2 weeks or more before labor beings and in multiparas, it may not occur until labor  Braxton Hicks Contractions  may be experienced throughout the pregnancy o Felt as tightening or pulling sensation on top of the uterus o Occur primarily in abdomen and groin and gradually spread downward before relaxing o Irregular contractions that can be decreased by walking, voiding, eating, increasing fluid intake, or changing position o Usually last about 30 seconds but can last up to 2 minutes o As birth gets closer, the uterus becomes more sensitive to oxytocin and the frequency and intensity of these contractions increases o If the contractions last longer than 30 secs and occur more than 4-6x/hr, the woman should contact her HCP so she can be evaluated for preterm labor  Backache  Bloody show o At the onset of labor or before, the mucous plug that fills the cervical canal is expelled as a result of cervical softening and increased pressure of the presenting part

o These ruptured capillaries release a small amount of blood that mixes with mucus resulting in the pink tinged secretions known as the bloody show  Spontaneous Rupture of Membranes o Rupture of membranes with loss of amniotic fluid prior to onset of labor  premature rupture of membranes (PROM) o The majority of women will begin labor within 24 hours o The rupture can result in either a sudden gush or a steady leakage of amniotic fluid o A continuous supply of amniotic is produced even though some is lost o After the amniotic sac has ruptured, the barrier to infection is gone and ascending infection is possible o There is also a danger of cord prolapse if engagement has not occurred  Increased Energy Level o Some women have a sudden increase in energy before labor o Sometimes this is referred to as nesting because the mother will use this time to prepare for the baby and spend time with other children o Usually occurs 24-48 hours before the onset of labor o Thought to be the result of an increase in epinephrine released caused by decreased progesterone  Weight loss  loses 1-3lbs True vs. False Labor pg. 457  False labor irregular uterine contractions are felt but the cervix is not affected o False labor, prodromal labor, Braxton Hicks  True labor  contractions occurring at regular intervals that increase in frequency, duration, and intensity o Bring about progressive cervical dilation and effacement

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Example: if a woman comes in and she goes from 2cm to 3 cm then back to 2cm and stays that way for hours, you would send her home because it’s not progressing Cervical Dilatations and Effacement  Dilatation is the opening of the cervix  Effacement is the thinning of the cervix

Theories of Onset of Labor  Oxytocin production  Prostaglandin  Estrogen stimulation  Fetal influences  Others “P’s” of Labor pg. 458  Passageway (birth canal)  Passenger (fetus and placenta)  Powers (contractions)  Position (maternal)  Psychological response Passageway pg. 458  Have to make sure the baby can come out  The birth passageway is the route through which the fetus must travel to be born vaginally  The passageway way consists of the maternal pelvis and soft tissues  The pelvis is the most important and it is typically assessed and measured during the first trimester to identify any abnormalities that might hinder vaginal birth  Relaxin and estrogen cause the connective tissues to become more relaxed and elastic and cause the joints to be more flexible to prepare the mother’s pelvis for birth Bony Pelvis  The maternal bony pelvis can be divided into the true and false portions  The false part is the upper part and the true pelvis is the bony passage through which the fetus must travel

o Made up of: the inlet, the mid-pelvis (cavity), and the outlet  To ensure the adequacy of the pelvic outlet for vaginal birth, these measurements are assessed: o Diagonal conjugate of the inlet (distance between the anterior surface of the sacral prominence and the anterior surface of the inferior margin of the symphysis pubis) o Transverse or ischial tuberosity diameter of the outlet (distance at the medial and lowest aspect of the ischial tuberosities, at the level of the anus, a known hand span or clenched-fist measurement is generally used to obtain this measurement) o True or obstetric conjugate (distance estimated from the measurement of the diagonal conjugate; 1.5cm is subtracted from the diagonal conjugate measurement)  If the diagonal conjugate measures at least 11.5cm and the true or obstetric conjugate measures 10cm of more (1.5cm less than diagonal conjugate, or about 10cm), then the pelvis is large enough for vaginal birth of what would be considered a normal sized newborn Pelvic Shape  The shape is a determining factor of a woman’s pelvis in addition to size  Each plane of the pelvis has a shape, which is defined by the anterior-posterior and transverse diameters  Gynecoid Pelvis o Considered the true female pelvis  40% of women o Vaginal birth is most favorable with this type because the inlet is round and the outlet is roomy o Optimal diameters in all 3 planes of the pelvis o Allows early and complete fetal internal rotation during labor and the sacrum is long, producing a deep pelvis o Vaginal birth is more favorable with the pelvic shape compared with android or platypelloid shape  Anthropoid Pelvis o Most common in men and most common in non-white women  25% of women o The pelvic inlet is oval  Android Pelvis o Considered the male shaped pelvis and is characterized by a funnel shape  20% of women o The pelvis inlet is heart shaped and the posterior segments are reduced in all pelvic planes o Descent of the fetal head into the pelvis is slow and failure of fetus to rotate is common o Prognosis is poor and usually leads to c-section  Platypelloid (flat) Pelvis o Least common type  3% incidence o Pelvic cavity is shallow but widens at the pelvic outlet, making it difficult for the fetus to descend through the mid-pelvis o Labor prognosis is poor with arrest in the inlet occurring frequently  usually require c-section

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A lot of women can have a combination of these 4 types of pelvises Regardless if the shape, a newborn can be born vaginally is size and positioning remain compatible The narrowest part of the fetus attempts to align itself with the narrowest part of the pelvic dimension

Soft Tissues  Soft tissues of the passageway consist of the cervix, the pelvic floor muscles, and the vagina  Through effacement, the cervix effaces to allow the presenting fetal part to descend into the vagina  The pelvic floor muscles help the fetus to rotate anteriorly as it passes through the birth canal  The soft tissues of the vagina expand to accommodate the fetus during birth Passenger  The fetus (with placenta) is the passenger  Important factors: the fetal head (size and presence of molding), fetal attitude (degree of body flexion), fetal lie (relationship of body parts), fetal presentation (first body part), fetal position (relationship to maternal pelvis), fetal station, and fetal engagement  Fetal Head o Largest fetal structure so it’s an important factor in relation to labor and birth o The bones that make up the face are fused but the five bones that make up the rest of the cranium (2 frontal bones, 2 parietal bones, and the occipital bone are not fused, they are soft and pliable, with gaps between the plates of bone) o The gaps between the plates of cranial bones are called sutures, and the intersections of these sutures are called fontanelles o Sutures are important because they allow the cranial bones to overlap in order for the head to adjust in shape when pressure is exerted on it by uterine contractions or the maternal bony pelvis o After birth, the sutures close as the bones grow and the brain reaches its full growth

o The changed (elongated) shape of the fetal skull at birth as a result of overlapping of cranial bones is known as molding o Fluid can collect in the scalp  caput succedaneum o Blood can collect beneath the scalp  cephalohematoma  These can further distort the shape and appearance of the fetal head o Caput succedaneum can be described as edema of the scalp as the presenting part  This swelling crosses suture lines and disappears within 3-4 days o Cephalohematoma is a collection of blood between periosteum and the bone that occurs several hours after birth  It does not cross suture lines and generally reabsorbed over the next 6-8 weeks o Sutures also play a role to help identify the position of the fetal head during a vaginal examination by palpation and can determine the position of the fetal head and degree of rotation that has occurred o Anterior and posterior fontanelles are also used to help identify the position of the fetal head  They allow for molding and are important when evaluating the newborn  Anterior fontanelle is the famous “soft spot,” it’s diamond shaped and measures from 1-4cm. it remains open for 12-18 months after birth to allow growth for the brain  The posterior fontanelle is located at the back of the fetal head and is triangular. It closes within 8-12 weeks after birth and measures 12cm at its widest diameter o The diameter of the fetal skull is an important consideration during the labor and birth process o Cephalic birth, 95% of births  If the fetus presents in a flexed position in which the chin is resting on the chest, the optimal or smallest fetal skull dimensions for vaginal birth are demonstrated o If the fetal head is not fully flexed at birth, the anteroposterior diameter

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increases and the increase might prevent the fetal skull from entering the maternal pelvis Fetal Attitude o Refers to the posturing (flexion or extension) of the joints and the relationship of fetal parts to one another o The most common fetal attitude is when labor begins is with all joints flexed  the fetal back is rounded, chin on chest, thighs are flexed on the abdomen, and legs are flexed at the knees o When the fetus presents to the pelvis with abnormal attitudes (no flexion or extension), their nonflexed position can increase the diameter of the presenting part as it passes through the pelvis, increasing the difficulty of birth o An attitude of extension tends to present larger fetal skull diameters, which may make birth difficult

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Fetal Lie o Refers to the relationship of the long axis (spine) of the fetus to the long axis (spine) of the mother o Three possible lies: longitudinal (most common), transverse, and oblique o A longitudinal lie occurs when the long axis of the fetus is parallel to that of the mother (fetal spine to maternal spine side by side) o A transverse lie occurs when the long axis of the fetus is perpendicular to the long axis of the mother (fetal spine lies across the maternal abdomen and crosses her spine o Oblique lie the fetal long axis is at an angle to the bony inlet, and no palpable fetal part is presenting o A fetus in a transverse or oblique lie position cannot be delivered vaginally

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Fetal Presentation o Refers to the body part of the fetus that enters the pelvic inlet first (the “presenting part”) o This is the fetal part that lies over the inlet of the pelvis or cervical os o 3 main fetal presentations: cephalic (head first), breech (pelvis first), and shoulder (scapula first) o Majority are cephalic  the presenting part is usually the occipital portion of the fetal head. This presentation is also called vertex presentation  military, brow, and facial presentations

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Breech Presentation o 97% actively turn to a cephalic presentation o determined by abdominal palpation o occurs when the buttocks or feet enter the maternal pelvis first and the fetal skull enters last o poses several challenges at birth  the largest part of the fetus (skull) is born last and may become “hung up” or stuck in the pelvis. The umbilical cord can become compressed between the fetal skull and maternal pelvis after the fetal chest is born because the head is last to exit o unlike the hard-fetal skull, the buttocks are soft and are not as effective as a cervical dilator during labor compared with cephalic o there is possibility of trauma to the head as a result of the lack of opportunity for molding

o the types of breech are determined by the positioning of the legs o frank breech  50-70% the buttocks present first with both legs extended upward toward the face o full or complete breech  5-10% the fetus sits crossed-legged above the cervix o footling or incomplete breech  10-30% one or both legs are presenting o breech presentations are associated with prematurity, placenta previa, multiparity, uterine abnormalities (fibroids), and some congenital anomalies o frank breech can result in vaginal birth but the other usually require c-section 

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Shoulder Presentation o Aka shoulder dystocia occurs when the fetal shoulders present first, with the head tucked inside o Signs appear while the woman is pushing as the head slowly extends and emerges over the perineum, but the retracts back into the vagina, commonly referred to as “turtle sign” o The fetus is in a transverse lie with the shoulder as the presenting part o Conditions associated  placenta previa, prematurity, high parity, PROM, multiple gestation, or fetal anomalies o C-section is usually necessary Fetal Position o The relationship of a given point on the presenting part of the fetus to a designated point of the maternal pelvis o The landmark fetal presenting parts include the occipital bone (O), which designates a vertex presentation, the chin (mentum M), which designates a breech presentation, and the scapula (acromion process A), which designates a shoulder presentation o The maternal pelvis is divided into 4 quadrants: right anterior, left anterior, right posterior, and left posterior. These designate whether the presenting part is directed toward the front, back, left, or right side o Fetal positioning is determined by identifying first the presenting part and then the maternal quadrant the presenting part is facing o Position is indicated by a three-letter abbreviation  The first letter defines whether the presenting part is tilted toward the left (L) or the right (R) side of the maternal pelvis  The second letter represents the particular presenting part of the fetus: O is for occiput, S is for sacrum, M is for mentum (chin), A is for acromion process, and D is for dorsal (fetal back) when denoting the fetal position in shoulder presentations  The third letter is the location of the presenting part in relation to the anterior (A) portion of the maternal pelvis or the posterior (P) portion of the maternal pelvis. If the presenting part is directed to the side of the maternal pelvis, the fetal presentation is designated as transverse (T)

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Fetal Station o Refers to the relationship of the presenting part to the level of the maternal pelvic ischial spines o Fetal station is measured in cm and referred to as minus or plus, depending on its location above or below the ischial spines o 0 station is designated when the presenting part is at the level of the maternal ischial spines, the distance is recorded as minus stations

o When the presenting part is below the ischial spines, the distance is recorded as plus stations o If the fetus is not descending past the ischial spines, then the station is negative and the cm # grows bigger from -1 to -4. The farther away the presenting part from the outside, the larger the negative # o The closer, the larger the positive # (+4cm) 

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Fetal Engagement o Signifies the entrance of the largest diameter of the presenting part into the smallest diameter of the maternal pelvis o The fetus is said to be engaged in the pelvis when the presenting part reaches 0 station  determined by pelvic exam o Occurs in primigravidas 2 weeks before term and multiparas can experience it several weeks before the onset of labor or not until it begins Cardinal Movements of Labor pg. 465 o The fetus goes through many positional changes as it travels through the passageway, these changes are known as cardinal movements o The movements are very precise to allow the smallest diameter of the fetal head to pass through corresponding diameter of the mother’s pelvic structure o Engagement  Occurs when the greatest transverse diameter of the head in vertex (biparietal diameter) passes though the pelvic inlet (usually 0 station). The head usually enters the pelvis with sagittal suture aligned in the transverse diameter o Descent  The downward movement of the fetal head until it is within the pelvic inlet  Occurs intermittently with contractions and is brought about by one or more of the following forces:  Pressure of the amniotic fluid  Direct pressure of the fundus on the fetus’s butt or head (depending on which part is located in the top of the uterus)  Contractions of the abdominal muscles (second stage)  Extension and straightening of the fetal body  Occurs throughout labor, ending with birth  Mother will be in discomfort o Flexion  Occurs when the vertex meets resistance from the cervix, the walls of the pelvis, or the pelvic floor  The chin is brought into contact with the fetal thorax and the presenting diameter is changed from occipitofrontal to suboccipitobregmatic, which achieves the smallest fetal skull diameter presenting to the maternal pelvic dimensions o Internal Rotation

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After engagement, as the head descends, the lower portion of the head (usually the occiput) meets resistance from one side of the pelvic floor  As a result, the head rotates 45 degrees anteriorly to the midline under the symphysis  this movement is known as internal rotation  Internal rotation brings the anteroposterior diameter of the head in line with the anteroposterior diameter of the pelvic outlet  It aligns the long axis of the fetal head with the long axis of the maternal pelvis  The widest portion of the maternal pelvis is the anteroposterior diameter, and the fetus must rotate to accommodate this pelvis o Extension  With further descent and full flexion of the head, the nucha (base of the occiput) becomes impinged under the symphysis  Resistance from the pelvic floor causes the fetal head to extend so that it can pass under the pubic the pubic arch  Extension occurs after internal rotation is complete  The head emerges through extension under the symphysis pubis along with the shoulders o External Rotation (Restitution)  After the head is born and is free of resistance, it untwists, causing the occiput to move ...