Cesarean Delivery with Deeply Impacted Fetal Head
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While various definitions have been proposed for impacted fetal head (IFH), all include the fetal head becoming deeply engaged within the maternal pelvis resulting in a difficult extraction. IFH complicates 1.5% of all cesarean births and up to 25% of emergent cesarean births. IFH is associated with an increased risk of maternal hemorrhage, hysterotomy extensions, and bladder injury, as well as neonatal hypoxia and traumatic injuries.
Risk factors for IFH include fetal malposition such as occiput posterior and occiput transverse positions, prolonged second stage, and failed operative vaginal delivery. Occiput posterior position, which occurs in approximately 10% of all births, results in a larger occipitofrontal diameter (11.5 cm) passing through the pelvic outlet. This is in contrast to fetuses in the occiput anterior position where the smaller suboccipitobregmatic diameter (9.5 cm) passes through the pelvic outlet. Occiput posterior position, which includes direct, left, and right occiput posterior positions, can be appreciated on digital vaginal examination by palpating the triangular posterior fontanelle formed by the junction of the sagittal and lambdoidal sutures posteriorly in the pelvis. Diagnosis is often complicated by fetal caput, and the rate of error for digital vaginal examination ranges from 30% to 65% in cohort studies. The use of transabdominal ultrasonography significantly improves accuracy in identifying fetal position.
When a cesarean birth is necessary and IFH is suspected, the nursing staff, anesthesiology team, and neonatology team should be informed. In the operating room, a modified lithotomy position, or “frog legging” the patient, can be used to improve access for an assistant. Because of distention of the lower uterine segment, hysterotomy should be made relatively high to avoid inadvertent entry through the cervix or vagina.
Several maneuvers have been described to manage IFH at the time of cesarean birth. The “push technique” is when the assistant places a hand into the vagina to disengage and elevate the fetal head into the uterus. Devices are also being explored, such as the Fetal Disimpacting System, to facilitate elevation of the fetal head to disengage it from its impacted position. With reverse breech extraction, or the “pull technique,” the surgeon initially extracts the feet through the hysterotomy and proceeds to deliver the rest of the fetus. Several studies from low-resource settings have found that the “pull technique” results in decreased maternal hemorrhage, hysterotomy extensions, and infection when compared with outcomes of the “push technique.” In cases of difficult extraction, a “J” or “T” extension may be required for successful fetal delivery through the hysterotomy, and uterine relaxation with nitroglycerin or terbutaline may be helpful to effect delivery.
Several additional techniques for cesarean delivery of a fetus with IFH have been described but have not been as well studied as the “push” and “pull” techniques. For example, a shoulder-first method can be used in which the shoulders are initially delivered through the hysterotomy, followed by traction placed on the axilla to facilitate delivery of the body and subsequently the head.
Jeve YB, Navti OB, Konje JC. Comparison of techniques used to deliver a deeply impacted fetal head at full dilation: a systematic review and meta-analysis. BJOG. 2016 Feb;123(3):337-45. doi: 10.1111/1471-0528.13593. Epub 2015 Aug 24. PMID: 26301522.
Barth WH Jr. Persistent occiput posterior. Obstet Gynecol. 2015 Mar;125(3):695-709. doi: 10.1097/AOG.0000000000000647. PMID: 25730235.
Lassey SC, Little SE, Saadeh et al. Cephalic Elevation Device for Second-Stage Cesarean Delivery: A Randomized Controlled Trial. Obstet Gynecol. 2020 Apr;135(4):879-884. doi: 10.1097/AOG.0000000000003746. PMID: 32168216; PMCID: PMC7098440.
Initial Publication April 2022
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