Umbilical cord prolapse may occur, particularly in the complete, footling, or kneeling<unk> . This is caused by the lowermost parts of the baby not completely filling the space of the dilated cervix. When the waters break the amniotic sac, it is possible for the umbilical cord to drop down and become compressed. This complication severely diminishes oxygen flow to the baby, so the baby must be delivered immediately (usually by Caesarean section) so that he or she can breathe. If there is a delay in delivery, the brain can be damaged. Among full-term, head-down babies, cord prolapse is quite rare, occurring in 0.4 percent. Among frank<unk>  babies the incidence is 0.5 percent, among complete<unk> es 5 percent, and among footling<unk> es 15 percent. Head entrapment is caused by the failure of the fetal head to negotiate the maternal midpelvis. At full term, the fetal bitrochanteric diameter (the distance between the outer points of the hips) is about the same as the biparietal diameter (the transverse diameter of the skull)—simply put the size of the hips are the same as the size of the head. The relatively larger buttocks dilate the cervix as effectively as the head does in the typical head-down presentation. In contrast, the relative head size of a preterm baby is greater than the fetal buttocks. If the baby is preterm, it may be possible for the baby's body to emerge while the cervix has not dilated enough for the head to emerge. Because the umbilical cord—the baby's oxygen supply—is significantly compressed while the head is in the pelvis during a<unk> , it is important that the delivery of the aftercoming fetal head not be delayed. If the arm is extended alongside the head, delivery will not occur. If this occurs, the Løvset manoeuvre may be employed, or the arm may be manually brought to a position in front of the chest. The Løvset manoeuvre involves rotating the fetal body by holding the fetal pelvis. Twisting the body such that an arm trails behind the shoulder, it will tend to cross down over the face to a position where it can be reached by the obstetrician's finger, and brought to a position below the head. A similar rotation in the opposite direction is made to deliver the other arm. In order to present the smallest diameter (9.5 cm) to the pelvis, the baby's head must be flexed (chin to chest). If the head is in a deflexed position, the risk of entrapment is increased. Uterine contractions and maternal muscle tone encourage the head to flex. Oxygen deprivation may occur from either cord prolapse or prolonged compression of the cord during birth, as in head entrapment. If oxygen deprivation is prolonged, it may cause permanent neurological damage (for instance, cerebral palsy) or death. It has been suggested that a fast vaginal delivery would mean the risk of stopping baby's oxygen supply is reduced. However, there is not enough research to show this and a quick delivery might cause more harm to the baby than a conservative approach to the birth. Injury to the brain and skull may occur due to the rapid passage of the baby's head through the mother's pelvis. This causes rapid decompression of the baby's head. In contrast, a baby going through labor in the head-down position usually experiences gradual molding (temporary reshaping of the skull) over the course of a few hours. This sudden compression and decompression in<unk>  may cause no problems at all, but it can injure the brain. This injury is more likely in preterm babies. The fetal head may be controlled by a special two-handed grip call the Mauriceau–Smellie–Veit maneuver or the elective application of forceps. This will be of value in controlling the rate of delivery of the head and reduce decompression. Related to potential head trauma, researchers have identified a relationship between<unk>  and autism. Squeezing the baby's abdomen can damage internal organs. Positioning the baby incorrectly while using forceps to deliver the after coming head can damage the spine or spinal cord. It is important for the birth attendant to be knowledgeable, skilled, and experienced with all variations of<unk> . Factors influencing safety * Birth attendant's skill (and experience with<unk>  – The skill of the doctor or midwife and the number of<unk> s previously assisted is of crucial importance. Many of the dangers in vaginal birth for<unk>  babies come from mistakes made by birth attendants. With the majority of<unk>  babies being delivered by cesarean section there is more risk that birth attendants will lose their skills in delivering<unk>  babies and therefore increase the risk of harm to the baby during a vaginal delivery. * Type of<unk>  presentation – the frank<unk>  has the most favorable outcomes in vaginal birth, with many studies suggesting no difference in outcome compared to head down babies. (Some studies, however, find that planned caesarean sections for all<unk>  babies improve outcome. The difference may rest in part on the skill of the doctors who delivered babies in different studies.) Complete<unk>  presentation is the next most favorable position, but these babies sometimes shift and become footling<unk> es during labour. Footling and kneeling<unk> es have a higher risk of cord prolapse and head entrapment. * Parity – Parity refers to the number of times a woman has given birth before. If a woman has given birth vaginally, her pelvis has "proven" it is big enough to allow a baby of that baby's size to pass through it. However, a head-down baby's head often molds (shifts its shape to fit the maternal pelvis) and so may present a smaller diameter than the same-size baby born<unk> . * Fetal size in relation to maternal pelvic size – If the mother's pelvis is roomy and the baby is not large, this is favorable for vaginal<unk>  delivery. However, prenatal estimates of the size of the baby and the size of the pelvis are unreliable. * Hyperextension of the fetal head – this can be evaluated with ultrasound. Less than 5% of<unk>  babies have their heads in the "star-gazing" position, face looking straight upwards and the back of the head resting against the back of the neck. Caesarean delivery is absolutely necessary, because vaginal birth with the baby's head in this position confers a high risk of spinal cord trauma and death. * Maturity of the baby – Premature babies appear to be at higher risk of complications if delivered vaginally than if delivered by caesarean section. * Progress of labor – A spontaneous, normally progressing, straightforward labor requiring no intervention is a favorable sign. * Second twins – If a first twin is born head down and the second twin is<unk> , the chances are good that the second twin can have a safe<unk> .
Breech birth
Preterm birth
Stillbirth
Coffin birth
Low birth weight
Multiple birth
Asynclitic birth
Water birth