- Author: Nan G O'Connell, MD; Chief Editor: Christine Isaacs, MD more...
Artificial Rupture of Amniotic Sac
Once amniotomy can be safely performed, the amniotic membrane perforator is advanced. If an amniotic hook is used, the handle of the device is held with one hand outside the vagina while 2 fingers of the opposite hand are placed in the vagina to guide the tip. Care should be taken to protect maternal tissues from the point. If an amniotic finger cot is used, the device is placed on the index or middle finger of the examining hand.
Once the hook reaches the amniotic sac, the tip is pushed up against the sac with the index or middle finger of the internal hand to pierce the membranes. The hook is then pulled through the membranes with the external hand holding the handle to create a hole in the sac. If an amniotic finger cot is being used, the pointed tip is dragged through the membranes with the finger to create the amniotomy.
The examining hand should remain in place to confirm that there has been no prolapse of the umbilical cord during the amniotomy.
The hand is then removed from the vagina The nature of the amniotic fluid (ie, clear, bloody, meconium-stained, or purulent) is documented, and the fetal heart rate should be monitored for several minutes after the procedure.
Approach to unengaged presenting part
If amniotomy is required but the presenting part is not well engaged, an assistant can apply external fundal or suprapubic pressure to keep the fetus in place while the amniotic fluid is slowly released. Before amniotomy, this pressure should be determined to be adequate to ensure that the fetal head is applied to the cervix.
When this technique is not feasible or has been attempted without success, a controlled amniotomy can be performed. In this instance, the patient should be taken to the cesarean suite and placed in the lithotomy position. A speculum is placed in the vagina, and the amniotic sac is visualized. A spinal needle is then used to make 1 or more small holes in the sac, thereby very slowly releasing amniotic fluid under direct visualization and allowing the presenting part to descend safely into the pelvis.
The most common complication of amniotomy is cord prolapse, which usually occurs during the sudden and rapid egress of amniotic fluid. Rupture of a vasa previa during amniotomy can cause life-threatening fetal blood loss. Both of these complications require emergency cesarean delivery.
An increased incidence of chorioamnionitis is seen, especially with prolonged rupture of membranes. Cord compression associated with variable decelerations of the fetal heart rate occurs more often after amniotomy. Minor fetal scalp trauma may also occur, especially if the fetal head is closely applied to the membranes when amniotomy is performed.
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