Labor can be too slow, but it also can be abnormally rapid. Precipitous labor and delivey is extremely rapid labor and delivery. It may result from an abnormally low resistance of the soft parts of the birth canal, from abnormally strong uterine and abdominal contractions, or rarely from the absence of painful sensations and thus a lack of awareness of vigorous labor.
Precipitous labor terminates in expulsion of the fetus in less than 3 hours. Using this definition, 25,260 live births-3 percent-were complicated by precipitous labor in the United States in 2013 (Martin, 2015). Despite this incidence, little published information describes maternal and perinatal outcomes.
For the mother, precipitous labor and delivery seldom are accompanied by serious maternal complications if the cervix is efaced appreciably and compliant, if the vagina has been stretched previously, and if the perineum is relxed. Conversely, vigorous uterine contractions combined with a long, firm cervix and a noncompliant birth canal may lead to uterine rupture or extensive lacerations of the cervix, vagina, vulva, or perineum (Sheiner, 2004). It is in these latter circumstances that amnionic-luid embolism most likely develops (Chap. 41, p. 785). Precipitous labor is frequently followed by uterine atony. The uterus that contracts with unusual vigor bore delivery is likey to be hypotonic ater delivey. In one report of 99 term pregnancies, short labors were more common in multiparas who typically had contractions at intervals less than 2 minutes. Precipitous labors have been linked to cocaine abuse and associated with placental abruption, meconium, postpartum hemorrhage, and low Apgar scores (Mahon, 1994).
For the neonate, adverse perinatal outcomes from rapid labor may be increased considerably for several reasons. he tumultuous uterine contractions, often with negligible intervals of relaxation, prevent appropriate uterine blood low and fetal oxygenation. Resistance of the birth canal may rarely cause intracranial trauma. Acker and coworkers (1988) reported that Erb or Duchenne brachial palsy was associated with such labors in a third of cases. Finally, during an unattended birth, the newborn may fall to the floor and be injured, or it may need resuscitation that is not immediately available.
As treatment, analgesia is unlikely to modiy these unusually forceful contractions to a significant degree. he use of tocolytic agents such as magnesium sulfate or terbutaline is unproven in these circumstances. Use of general anesthesia with agents that impair uterine contractibility such as isoflurane is often excessively heroic. Certainly, any oxytocin being administered should be stopped immediately.
Fetopelvic disproportion arises from diminished pelvic capacity, from abnormal fetal size or presentation, or more usually from both. he pelvic inlet, midpelvis, or pelvic outlet may be contracted solely or in combination. ny contraction of the pelvic diameters that diminishes pelvic capacity can create dystocia during labor. Normal pelvic dimensions are additionally discussed and illustrated in Chapter 2 (p. 30).