Fetal "presentation" is different from fetal "position." Fetal position refers to the orientation of the fetus within the birth canal (eg, looking toward the mother's pubic bone (OP), or look toward the mother's coccyx (OA), etc.)
Complete breech means the fetal thighs are flexed along the fetal abdomen, but the fetal shins and feet are tucked under the legs. The buttocks is presenting first, but the feet are very close. Sometimes during labor, a complete breech will shift to an incomplete breech if one or both of the feet extend below the fetal buttocks.
While many breech fetuses deliver vaginally without incident, this presentation is associated with an increased risk of:
For these reasons, many breech babies are delivered by cesarean section, and some obstetricians feel that all breech babies should be delivered in this way.
If labor is allowed to continue for enough time with the fetus in transverse lie, the uterus will rupture. Even before the uterus ruptures, there is an increased risk in this presentation for prolapsed umbilical cord. For these reasons, women found to have a transverse lie in labor will usually have a cesarean section.
There are some exceptions to this indication for cesarean section:
Some predisposing factors for a transverse lie include:
Transverse lie occurs frequently in early pregnancy, when it is of no consequence. At 16 weeks gestation, about half of all pregnancies will be transverse lie. This number steadily falls as pregnancy advances and the incidence of transverse lie by the 28th week is well below 10%. It falls steadily thereafter.
Whenever a fetal transverse lie is encountered near term or in labor, evaluate the patient carefully with ultrasound to determine if there are any predisposing factors, such as a placenta previa or pelvic kidney that could modify your management of the patient. So long as a placenta previa is not present, many obstetricians will check the patient's cervix at frequent intervals to detect early cervical dilatation and the consequential increased risk of cord prolapse. Sometimes, these patients are delivered early by scheduled cesarean section to avoid that risk.
A compound presentation may be resolvable if the fetus can be encouraged to withdraw the hand, for example.
If the fetus and arm are relatively small in comparison to the maternal pelvis, vaginal delivery may still be possible, but with some risk of injury to the arm.
If the fetus and arm are relatively large in comparison to the maternal pelvis, obstructed labor will occur and a cesarean will be needed.
OB-GYN 101: Introductory
Obstetrics & Gynecology
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