A. Obstetric Pelvis 1. What is the job of the false pelvis? The false pelvis lies superior to the true pelvis and linea terminalis. It is a larger and wider basin that supports the enlarged uterus during pregnancy, as well as the intestines. 2. Name the 3 parts of the true pelvis. The three parts of the true pelvis are the inlet, the pelvic cavity, and the pelvic outlet. 3. What are the 4 classifications of the pelvis? The four classifications of the pelvis are the gynecoid, the android, the anthropoid, and the platypelloid. 4. Concerning the above types of pelvises, what effect does each have on: labor, engagement of the fetal head, and overall birth prognosis? The gynecoid pelvis during labor reduces perineal tears during labor, and contributes to spontaneous delivery. The uterus functions well, reducing in size when it’s supposed to. The fetus also successfully rotates throughout the birth canal early, and completely. The fetal head will engage in the transverse or oblique diameter, meaning the back of the head will face the lateral or diagonal sides of the pelvis such as the pectineal or arcuate line. With the head engaged in these starting positions, the fetus will also be in a slight asynclitism, meaning the fetus’ head will be tipped towards one shoulder, with its body and head not going in a completely straight line downwards. The fetus has good flexion, with his chin tucked in his chest and is in the common occiput anterior position, where the back of his head is facing down and toward the pubic symphysis. The gynecoid often results in a good prognosis. Android pelvises result in a poor overall birth prognosis. During labor there’s an increase in major perineal tears. Most commonly, the fetus will engage in a deep transverse arrest, or in an occiput posterior position with no continued rotation. The back of the fetal head will face the sacrum in this position. It is a difficult delivery with the use of forceps to rotate and extract the baby. The fetal head is in a transverse or posterior diameter in asynclitism as well. There is extreme modeling done on the head. The anthropoid pelvis during labor and delivery is usually easy, with the fetal face commonly facing the pubis. The fetus engages in an anteroposterior or oblique position, which explains the occiput posterior position during delivery. This pelvis has a good overall prognosis. Finally, the platypelloid has a very poor overall birth prognosis, which is usually ending in cesarean section. During labor there is a delay at the inlet of the pelvis, which is just the start. The fetus also engages in a transverse diameter with marked asynclitism. 5. What are the reasons for these differences? Explain for each type of pelvis why there are differences in labor, engagement, and prognosis for birth. The gynecoid pelvis is a normal female pelvis, which is 50% of women have. There is a smaller amount of perineal tears due to the wide pubic arch in the gynecoid pelvis, allowing for a wider area already “stretched” that prevents tearing. Due to its round and wide false pelvis, the uterus is heavily supported during its largest moment to perform good uterine function during birth. The inlet of the pelvis, has a well rounded forepelvis in the anterior segment, and a broad, deep and roomy posterior segment. These two segments allow for a large, roomy space to have good initial engagement at the inlet. The sacrum having a deep curve, short length, and sloping backwards helps the fetus internally rotate midway through the pelvis, due to the larger amount of space. The ischial spines are not prominent, and the sidewalls of the pelvis are parallel and straight which allow for an easy descent with no parts too narrow to get stuck in. The iliopectineal line of the pelvis is average, reducing the amount of passage the fetus needs to travel. Finally, the outlet has a short inferior pubic rami, adequate capacity, and a long anteroposterior diameter which will give more space for the fetal head to birth in an occiput posterior or anterior (more common) position, compared to transverse. The android pelvis on the other hand is shaped more like a males pelvis. It is in the shape of a heart of wedge, with a very short and inadequate posterior sagittal diameter at the inlet. The posterior segment also is shallow, and the sacral promontory indents protrude into the inlet, reducing the space. Also, the anterior segment and forepelvis is narrow, and sharply angulated. Because of this, the fetal head engages transversely or posteriorly, ending with a deep transverse arrest. In the midpelvis, all the diameters are reduced, decreasing the movement capability of the fetus. This makes it very difficult for the fetus to rotate internally, causing the use of forceps. The sacrum is flat, inclined forward, long, narrow, and heavy. The sidewalls are convergent and are the shape of a funnel, while the ischial spines are prominent. The depth of the pelvis is long. All of these factors in the midpelvis reduce the capacity, and make it uncomfortable for both the mother and the baby during labor. The sacrum and sidewalls with these features especially will inhibit the descent of the baby. At the outlet, the narrow and deep pubic arch will increase major perineal tears. The transverse diameter at the outlet is narrow while the anteroposterior diameter is very short, continuing to reduce the birth canal making it harder for the birth of the fetus, This is when forceps would be used. The anthropoid pelvis is very apelike and resembles the gynecoid pelvis the most. Starting at the inlet, it’s an oval shape, so it has a long anteroposterior, anterior sagittal, and posterior sagittal diameter. Most of the pelvis is longer and deeper than the gynecoid, but not wide. Due to this, the fetus engages in the anteroposterior or oblique position but not transverse because it is not wide enough. The midpelvis becomes more adequate like the gynecoid, with a long anteroposterior diameter. It has a narrow, long, and backwardly inclined sacrum. The sidewalls are straight, the depth is long, with an adequate capacity. The outlet of the pelvis again has a long anteroposterior diameter, normal transverse diameter, and normal or a bit narrow of a pubic arch. I believe the fetus’s face to pubis is due to the longer anteroposterior diameters throughout the entire pelvis, allowing for a roomier place for the fetus’s head/face to guide through. The prognosis is good like the gynecoid pelvis because of its oval shape allowing the fetus to engage the occiput anterior or posterior position. The platypelloid is very rare, and the most complicated pelvis during birth. It is considered to have a transverse oral shape and the inlet of the pelvis contains a short anteroposterior diameter, while having a long transverse diameter. The posterior sagittal diameter is very short like the android pelvis, as well as the anterior sagittal diameter, unlike the android. Which I believe is what makes engagement more difficult to achieve than the android pelvis. In the midpelvis, the anteroposterior diameter is shortened, making a tighter space for the fetal head to stay engaged or to rotate and engage into an occiput anterior or posterior position. Instead, the transverse diameter is wider, allowing more room and comfort for the fetus to position itself transversely, but even then, there is delay at the inlet already before this point. The inlet of the platypelloid is shaped like a kidney and makes it extremely difficult to engage the fetal head. Although, the outlet is more favorable for birth, and if the fetal head were to engage, there could be a possibility of the fetus passing the rest of the birth canal smoothly. B. The Fetus 1. What are fetal sutures? List the main fetal sutures. Fetal sutures are the spaces between the bones of the skull that are made up of membranes. They are soft fibrous tissues that link the bones. The main fetal sutures are: sagittal suture, lambdoidal sutures (“last” sutures), coronal sutures (“cornea” sutures in the front like the eyes), frontal sutures. 2. Name the two important aspects of the sutures. The two most important aspects of the fetal sutures are that they enable molding of the fetal head, and they are used to identify fetal positioning. During labor, fetal molding allows the bones to overlap under pressure while the fetal head is being compressed throughout the pelvis. It also allows for the brain to expand and grow as the baby develops. During a vaginal exam, understanding the fetal sutures will help the midwife diagnose the fetal head position within the pelvis. 3. What are fontanelles? Fontanelles are soft membrane-filled spaces that are seperated from the bones by the fetal sutures. They are covered with a tough, fibrous membrane. 4. What are the two main purposes of the fontanelles? Like the fetal sutures, the fontanelles also contribute to diagnosing the position of the fetus in the pelvis. On the other hand, the anterior fontanelle bregma is evaluated to determine the condition of the baby after birth. For instance, if the baby is dehydrated, the anterior fontanelle will be depressed and sinking below the surface of the skull. If the fontanelle is bulging, tense, and raised above the level of the skull, this means there is an increase in intracranial pressure. 5. Name the two fontanelles. The two fontanelles are the anterior fontanelle, and the posterior fontanelle. 6. What are the 8 landmarks of the fetal skull? The 8 landmarks of the fetal skull from back to front are: the occiput, the posterior fontanelle, the vertex, the anterior fontanelle, the sinciput, the glabella, the nasion, and the parietal bosses.