Shoulder presentation | |
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A shoulder presentation with a prolapsed arm, by William Smellie | |
Specialty | Obstetrics |
In obstetrics, a shoulder presentation is a malpresentation at childbirth where the baby is in a transverse lie (its vertebral column is perpendicular to that of the mother), thus the leading part (the part that first enters the birth canal) is an arm, a shoulder, or the trunk. While a baby can be delivered vaginally when either the head or the feet/buttocks are the leading part, it usually cannot be expected to be delivered successfully with a shoulder presentation unless a cesarean section (C/S) is performed.
Shoulder presentations are uncommon (about 0.5% of births) [1] since, usually, toward the end of gestation, either the head or the buttocks start to enter the upper part of the pelvis, anchoring the fetus in a longitudinal lie. It is not known in all cases of shoulder presentation why the longitudinal line is not reached, but possible causes include bony abnormalities of the pelvis, uterine abnormalities such as malformations or tumors (fibroids), or other tumors in the pelvis or abdomen. Other factors are a lax abdominal musculature, uterine overdistension (i.e., polyhydramnios), multiple gestation, placenta previa, a small fetus, or a fetus with some abnormality. Further, if the amniotic fluid sac ruptures, the shoulder or arm may become wedged as a shoulder presentation.
Inspection of the abdomen may already give a clue as it is wide from side to side. Usually performing the Leopold's maneuvers will demonstrate the transverse lie of the fetus. [2] Ultrasound examination delivers the diagnosis and may indicate possible causes such as multiple gestation or a tumor. On vaginal examination, the absence of a head or feet/breech is apparent.
Shoulder presentations are classified into four types, based on the location of the scapula:
While a transverse lie prior to labor can be manually versed to a longitudinal lie, once the uterus starts contracting the uterus normally will not allow any version procedure. A shoulder presentation is an indication for a caesarean section. Generally, as it is diagnosed early, the baby is not damaged by the time of delivery. With the rupture of the membranes, there is an increased risk of a cord prolapse as the shoulder may not completely block the birth canal. Thus the caesarean section is ideally performed before the membranes break.
The delivery of the second twin in a transverse lie with a shoulder presentation represents a special situation that may be amenable to a vaginal delivery. As the first twin has just been delivered and the cervix is fully dilated the obstetrician may perform an internal version, that is inserting one hand into the uterus, find the baby’s feet, and then bring the baby into a breech position and deliver the baby as such. [3]
During labor the shoulder will be wedged into the pelvis and the head lie in one iliac fossa, the breech in the other. With further uterine contractions the baby suffocates. [1] The uterus continues to try to expel the impacted fetus and as its retraction ring rises, the musculature in the lower segments thins out leading eventually to a uterine rupture and the death of the mother. [1] [4] Impacted shoulder presentations contribute to maternal mortality. [5] Obviously a cesarean section should be performed before the baby has died, but even when the baby has died or impaction has occurred, C/S is the method of choice of delivery, as alternative methods of delivery are potentially too traumatic for the mother. If the baby is preterm or macerated and very small a spontaneous delivery has been observed. [1]
Prior to the arrival of C/S the fetus usually died during protracted labor and the mother's life was at risk as well due to infection, uterine rupture and bleeding. On occasion, if the baby was macerated and small, it collapsed sufficiently to be delivered. The shoulder presentation was a feared obstetrical complication.
In 1690 Justine Siegemundin, a German midwife, published Die Kgl. Preußische und Chur-Brandenburgische Hof-Wehemutter. This treatise for midwives demonstrated abnormal presentations at birth and their management. She was the first to describe a two-handed method of performing an internal rotation of the baby to extract it as a breech (a variation of which is performed today on the second twin, see above) using a sling. [6] The procedure was useful provided the fetus was not impacted. Once the uterus had contracted around the baby tightly, destructive interventions were used to save the life of the mother. [7]
Caesarean section, also known as C-section, cesarean, or caesarean delivery, is the surgical procedure by which one or more babies are delivered through an incision in the mother's abdomen. It is often performed because vaginal delivery would put the mother or child at risk. Reasons for the operation include obstructed labor, twin pregnancy, high blood pressure in the mother, breech birth, shoulder presentation, and problems with the placenta or umbilical cord. A caesarean delivery may be performed based upon the shape of the mother's pelvis or history of a previous C-section. A trial of vaginal birth after C-section may be possible. The World Health Organization recommends that caesarean section be performed only when medically necessary.
A breech birth is when a baby is born bottom first instead of head first, as is normal. Around 3–5% of pregnant women at term have a breech baby. Due to their higher than average rate of possible complications for the baby, breech births are generally considered higher risk. Breech births also occur in many other mammals such as dogs and horses, see veterinary obstetrics.
Placenta praevia is when the placenta attaches inside the uterus but in a position near or over the cervical opening. Symptoms include vaginal bleeding in the second half of pregnancy. The bleeding is bright red and tends not to be associated with pain. Complications may include placenta accreta, dangerously low blood pressure, or bleeding after delivery. Complications for the baby may include fetal growth restriction.
External cephalic version (ECV) is a process by which a breech baby can sometimes be turned from buttocks or foot first to head first. It is a manual procedure that is recommended by national guidelines for breech presentation of a pregnancy with a single baby, in order to enable vaginal delivery. It is usually performed late in pregnancy, that is, after 36 gestational weeks, preferably 37 weeks, and can even be performed in the early stages of childbirth.
Umbilical cord prolapse is when the umbilical cord comes out of the uterus with or before the presenting part of the baby. The concern with cord prolapse is that pressure on the cord from the baby will compromise blood flow to the baby. It usually occurs during labor but can occur anytime after the rupture of membranes.
A hysterotomy is an incision made in the uterus. This surgical incision is used in several medical procedures, including during termination of pregnancy in the second trimester and delivering the fetus during caesarean section. It is also used to gain access and perform surgery on a fetus during pregnancy to correct birth defects, and it is an option to achieve resuscitation if cardiac arrest occurs during pregnancy and it is necessary to remove the fetus from the uterus.
Placental abruption is when the placenta separates early from the uterus, in other words separates before childbirth. It occurs most commonly around 25 weeks of pregnancy. Symptoms may include vaginal bleeding, lower abdominal pain, and dangerously low blood pressure. Complications for the mother can include disseminated intravascular coagulopathy and kidney failure. Complications for the baby can include fetal distress, low birthweight, preterm delivery, and stillbirth.
Obstructed labour, also known as labour dystocia, is the baby not exiting the pelvis because it is physically blocked during childbirth although the uterus contracts normally. Complications for the baby include not getting enough oxygen which may result in death. It increases the risk of the mother getting an infection, having uterine rupture, or having post-partum bleeding. Long-term complications for the mother include obstetrical fistula. Obstructed labour is said to result in prolonged labour, when the active phase of labour is longer than 12 hours.
Prelabor rupture of membranes (PROM), previously known as premature rupture of membranes, is breakage of the amniotic sac before the onset of labour. Women usually experience a painless gush or a steady leakage of fluid from the vagina. Complications in the baby may include premature birth, cord compression, and infection. Complications in the mother may include placental abruption and postpartum endometritis.
In case of a previous caesarean section a subsequent pregnancy can be planned beforehand to be delivered by either of the following two main methods:
Uterus didelphys represents a uterine malformation where the uterus is present as a paired organ when the embryogenetic fusion of the Müllerian ducts fails to occur. As a result, there is a double uterus with two separate cervices, and possibly a double vagina as well. Each uterus has a single horn linked to the ipsilateral fallopian tube that faces its ovary.
A vaginal delivery is the birth of offspring in mammals through the vagina. It is the most common method of childbirth worldwide. It is considered the preferred method of delivery, as it is correlated with lower morbidity and mortality than caesarean sections (C-sections), though it is not clear whether this is causal.
An asynclitic birth or asynclitism are terms used in obstetrics to refer to childbirth in which there is malposition of the head of the fetus in the uterus, relative to the birth canal. Asynclitic presentation is different from a shoulder presentation, in which the shoulder is presenting first. Many babies enter the pelvis in an asynclitic presentation, and most asynclitism corrects spontaneously as part of the normal birthing process.
In obstetrics, position is the orientation of the fetus in the womb, identified by the location of the presenting part of the fetus relative to the pelvis of the mother. Conventionally, it is the position assumed by the fetus before the process of birth, as the fetus assumes various positions and postures during the course of childbirth.
In obstetrics, the presentation of a fetus about to be born specifies which anatomical part of the fetus is leading, that is, is closest to the pelvic inlet of the birth canal. According to the leading part, this is identified as a cephalic, breech, or shoulder presentation. A malpresentation is any presentation other than a vertex presentation.
In obstetrics, a cephalic presentation or head presentation or head-first presentation is a situation at childbirth where the fetus is in a longitudinal lie and the head enters the pelvis first; the most common form of cephalic presentation is the vertex presentation, where the occiput is the leading part. All other presentations are abnormal (malpresentations) and are either more difficult to deliver or not deliverable by natural means.
An obstetric labor complication is a difficulty or abnormality that arises during the process of labor or delivery.
Locked twins is a rare complication of multiple pregnancy where two fetuses become interlocked during presentation before birth. It occurs in roughly 1 in 1,000 twin deliveries and 1 in 90,000 deliveries overall. Most often, locked twins are delivered via Caesarean section, given that the condition has been diagnosed early enough. The fetal mortality rate is high for the twin that presents first, with over 50% being stillborn.
Prolonged labor is the inability of a woman to proceed with childbirth upon going into labor. Prolonged labor typically lasts over 20 hours for first time mothers, and over 14 hours for women that have already had children. Failure to progress can take place during two different phases; the latent phase and active phase of labor. The latent phase of labor can be emotionally tiring and cause fatigue, but it typically does not result in further problems. The active phase of labor, on the other hand, if prolonged, can result in long term complications.
Emergency childbirth is the precipitous birth of an infant in an unexpected setting. In planned childbirth, mothers choose the location and obstetric team ahead of time. Options range from delivering at home, at a hospital, a medical facility or a birthing center. Sometimes, birth can occur on the way to these facilities, without a healthcare team. The rates of unplanned childbirth are low. If the birth is imminent, emergency measures may be needed. Emergency services can be contacted for help in some countries.