Which fetal presentation is best

References: [1]. Expand all sections Register Log in. Trusted medical expertise in seconds. Find answers fast with the high-powered search feature and clinical tools. Try free for 5 days Evidence-based content, created and peer-reviewed by physicians. Read the disclaimer. Mechanics of childbirth.

The best position for the baby to be in to pass through the pelvis is with the head down and the body facing towards the mother's back. This position is called occiput anterior OA.

In breech position, the baby's bottom is facing down instead of the head. Your health care provider will most often detect this in an office visit before your labor begins. Most babies will be in the head-down position by about 34 weeks. Part of your prenatal care after 34 weeks will involve making sure your baby is in the head-down position. If your baby is breech, it is not safe to deliver vaginally.

If your baby is not in a head-down position after your 36th week, your provider can explain your choices and their risks to help you decide what steps to take next. In occiput posterior position, your baby's head is down, but it is facing the mother's front instead of her back. It is safe to deliver a baby facing this way. But it is harder for the baby to get through the pelvis. If a baby is in this position, sometimes it will rotate around during labor so that the head stays down and the body faces the mother's back OA position.

The mother can walk, rock, and try different delivery positions during labor to help encourage the baby to turn.

Fetal presentation is a reference to the part of the fetus that is overlying the maternal pelvic inlet. The most common relationship between fetus and mother is the longitudinal lie, cephalic presentation. A breech fetus also is a longitudinal lie, with the fetal buttocks as the presenting part. Breech fetuses also are referred to as malpresentations because of the many problems associated with them.

Fetuses that are in a transverse lie may present the fetal back or shoulders, as in the acromial presentation , small parts arms and legs , or the umbilical cord as in a funic presentation to the pelvic inlet. In an oblique lie, the fetal long axis is at an angle to the bony inlet, and no palpable fetal part generally is presenting. This lie usually is transitory and occurs during fetal conversion between other lies.

The most dependent portion of the presenting part is known as the point of direction. The occiput is the point of direction of a well-flexed fetus in cephalic presentation.

The fetal position refers to the location of the point of direction with reference to the four quadrants of the maternal outlet as viewed by the examiner.

Thus, position may be right or left as well as anterior or posterior. Fetal attitude refers to the posture of a fetus during labor. Mammalian fetuses have a tendency to assume a fully flexed posture during development and during parturition.

Flexion of the fetal head on the chest allows for the delivery of the head by its smallest bony diameter. A loss of this flexed posture presents a progressively larger fetal head to the bony pelvis for labor and delivery Fig.

The fetal arms and legs also tend to assume a fully flexed posture. The longitudinal posture of the fetus likewise is flexed under normal circumstances. Importance of cranial flexion is emphasized by noting the increased diameters presented to the birth canal with progressive deflection. Flexed head. Military position. Progressive deflection. The mechanism of labor and delivery, as well as its inherent safety and efficacy, is determined by the specifics of the fetopelvic relationship at the onset of labor.

Further correlations with fetopelvic relationships are important before birth. The relative incidence of differing fetopelvic relations varies with diagnostic and clinical approaches to care. Among longitudinal lies, about 1 in 25 fetuses are not cephalic but breech at the onset of labor. As pregnancy proceeds to term, most fetuses assume a longitudinal lie with relationship with the maternal outlet.

Conversely, when labor and delivery are considered to be remote from term, the proportion of fetuses in abnormal and suboptimal locations increases Table 1. Gestational age weeks. Transverse and oblique lies also are seen with greater frequency earlier in gestation. A fetus in a transverse lie may present the shoulder or acromion as a point of reference to the examiner.

As term approaches, spontaneous conversion to a longitudinal lie is the norm. As seen with breech presentation, there is a rapid decrease in nonaxial lie during the third trimester. With the comprehensive application of ultrasound in the antepartum period, discovery of a transverse or oblique lie has increased.

However, nonaxial fetal lies usually are transitory. Abnormal fetal lie frequently is seen in multifetal gestation, particularly with the second twin.

A transverse lie may be encountered with large discrepancies in fetopelvic parameters, such as exist with extreme prematurity and macrosomia. This tendency is greater in women of grand parity, in whom relaxation of the abdominal and uterine musculature is cited as the predisposing factor.

Distortion of the uterine cavity shape, such as that seen with leiomyomas, prior uterine surgery, or developmental anomalies Mullerian fusion defects , coexists with both abnormalities in fetal lie and malpresentation. Placental location also may play a contributing role.

Fundal and cornual implantation are seen more frequently in breech presentation. Placenta previa is a well-described concomitant in both transverse lie and breech presentation.

Congenital anomalies of the fetus also are seen in association with abnormalities in either presentation or lie. Abnormalities seen include chromosomal autosomal trisomy and structural abnormalities hydrocephalus , as well as syndromes of multiple effects fetal alcohol syndrome Table 2. CNS, central nervous system; GU, genitourinal.

The incidence in breech delivery is three times greater when controlled for gestational age. Among premature breech infants, the incidence is even greater, as it is for all fetuses born prematurely. Prematurity is a crucial factor in the incidence as well as the clinical implications of abnormal fetal lie and malpresentation.

Fetal size and shape undergo dramatic change during the second and third trimester Fig. Chicago, Year Book Medical Publishers, The shape of the fetus is highly dependent on gestational age. The relationship of the three diameters that approximate shape biparietal, bisacromial, and intertrochanteric becomes more favorable as gestational age reaches term. This is commonly reflected by ultrasound measurements of the head circumference and abdominal circumference reaching unity.

Because the fetus has a relatively larger head than body during most of the late second and early third trimester, the fetus tends to spend much of its time in breech presentation or in a nonaxial lie as it rotates back and forth between cephalic and breech presentations. The relatively large volume of amniotic fluid present facilitates these dynamics.

Breech presentation is more common at earlier gestation and therefore is seen more frequently among low-birth weight infants 4 Table 4.

Breech infants are more likely to be small for gestational age regardless of their gestation at delivery. The small size of the premature fetus is further compromised by the specific malpresentations that occur. With less neurologic and muscular control, deflexed or even extended varieties of fetal presentations are seen.

Deflexion of the fetal head, more commonly seen in preterm fetuses, results in the potential for further compromise at delivery. Philadelphia, JB Lippincott, Table 6. Type of breech presentation in labor by gestational age. Variations of breech presentations. Thus, the problems associated with abnormal lie and malpresentation are most frequent and of greatest consequence in preterm labor and delivery.

At term, similar, though usually less dramatic, consequences may be seen with fetuses who are in abnormal positions. Perinatal morbidity and mortality is threefold higher in breech presentation than cephalic presentation.

Much of this excessive compromise is caused by factors that are not directly preventable. In a different population, Todd and Steer 6 found that 23 of 34 term breech deaths among term infants were not related to complications of breech delivery but were associated with anomalies, infection, and isoimmunization. As noted earlier, preterm and small-for-gestational age infants commonly are associated with breech labor and delivery.

As for term breech infants, experience indicates that most of the adverse outcomes seen are unrelated to breech delivery. Thus, for all breech fetuses, about one third of the excessive perinatal loss falls to birth trauma and asphyxia. The complications associated with abnormal fetal lie and malpresentations include both maternal and fetal. As noted earlier, prematurity and malpresentation are strongly related.

Circumstances in which premature birth may occur also include maternal complications such as pregnancy-induced hypertension and medical complications cardiovascular, neoplastic , as well as obstetric problems such as premature rupture of membranes and chorioamnionitis. The circumstances dictating delivery may further compromise the preterm fetus. The obstetric complications for the fetus include a diverse group of misadventures.

Prolapse of the umbilical cord, intrauterine infection, maldevelopment as a result of oligohydramnios, asphyxia, and birth trauma all are concerns. Birth trauma, particularly to the head and cervical spine, is a significant risk to both term and preterm infants who present as breech presentation or in a nonaxial lie.

Therefore, small alterations in the dimensions or shape of the maternal bony pelvis or the attitude of the fetal head may have grave consequences. As discussed earlier, this process is of greater risk to the preterm infant because of the relative size of the fetal head and body. Trauma to the head is not eliminated by cesarean section; both intracranial and cervical spine trauma may result from entrapment in either the uterine or abdominal incisions.

The fetus in the transverse lie, regardless of gestational age, generally requires cesarean delivery. At cesarean section, delivery may be aided by converting the fetus to a longitudinal lie for the delivery after entering the abdomen.

This conversion may allow for the use of a transverse incision into the uterus instead of the more morbid vertical incision. External cephalic version ECV should be considered in a nonlaboring patient. When the diagnosis is first made at term, spontaneous conversion to a longitudinal lie is less common than for its breech counterpart.

This results from the higher incidence of structural causes for the transverse lie. When abnormal presentation or lie occurs in a twin gestation, management includes a greater range of options. The conversion of a backup transverse second twin, either by internal or external version at the time of delivery, is an option for the experienced clinician. When the back is down at the time of delivery, the prudent course for the delivery of a fetus in transverse lie is by cesarean section. Strong consideration should be given to the incisions at delivery in this circumstance, with a vertical uterine incision being used liberally.

When a fetus in a transverse lie is diagnosed remote from delivery, as occurs at time of ultrasound, the physician is faced with an additional dilemma. Spontaneous rupture of membranes may result in cord prolapse or compromise with the risk of fetal asphyxia. Delivery at the time of antepartum ultrasound before term may result in jeopardy because of prematurity.

External version, as a correction, may be attempted as long as ultrasound excludes placenta previa and documents an appropriate amount of amniotic fluid. Experience has demonstrated some success, although in general, the use of ECV is more likely to be successful for a breech-presenting fetus. The patient should be carefully counseled about the problem and its inherent risks.

Hospitalization and observation may be considered. However, the cost—benefit ratio in this era of managed care makes prolonged hospitalization unlikely under most circumstances. I recommend twice-weekly fetal surveillance to assess for cord compromise. The patient should be warned about the signs and symptoms of preterm labor and encouraged to present to labor and delivery should these conditions arise. Under certain circumstances, home uterine activity monitoring may provide a useful adjunct.

The antepartum diagnosis of persistent breech presentation is accompanied by similar concerns. In addition, careful evaluation for fetal anomalies is warranted. It is the most common abnormal position or presentation. When a fetus faces up, the neck is often straightened rather than bent, and the head requires more space to pass through the birth canal.

Delivery by a vacuum extractor or forceps Operative Vaginal Delivery Operative vaginal delivery is delivery using a vacuum extractor or forceps. A vacuum extractor consists of a small cup made of a rubberlike material that is connected to a vacuum. It is inserted Doctors use a cesarean delivery In breech presentation, the buttocks or sometimes the feet present first.

It is the second most common type of abnormal presentation. When delivered vaginally, babies that present buttocks first are more likely to be injured than those that present head first. Such injuries may occur before, during, or after birth. The baby may even die. Complications are less likely when breech presentation is detected before labor or delivery. Labor starts too soon preterm labor Preterm Labor Labor that occurs before 37 weeks of pregnancy is considered preterm.

Babies born prematurely can have serious health problems. The diagnosis of preterm labor is usually obvious. Measures such The uterus is abnormally shaped or contains abnormal growths such as fibroids Fibroids A fibroid is a noncancerous tumor composed of muscle and fibrous tissue.

It is located in the uterus. Fibroids can cause pain, abnormal vaginal bleeding, constipation, repeated miscarriages The fetus has a birth defect Overview of Birth Defects Birth defects, also called congenital anomalies, are physical abnormalities that occur before a baby is born. They are usually obvious within the first year of life.