Amniotomy

Rationale for Compliance	Evidence Grade
Amniotomy is believed to shorten labor and, by so doing, reduce the number of cesarean sections for slow progress and improve neonatal outcomes by reducing exposure to the stress of overly long labors. However:		NEB
• Routine amniotomy shortens mean duration of labor by only a modest amount (1–2 hrs) (Fraser, 1999).	Quality:	B a
	Quantity:	A
	Consistency:	A**
• Early amniotomy has less effect than amniotomy later in labor (Fraser, 1993).	Quality:	B
	Quantity:	A
	Consistency:	N*
• Routine amniotomy fails to reduce the cesarean section rate (Fraser, 1999; Rouse, 1994).	Quality:	B a
	Quantity:	A
	Consistency:	B (Of 10 trials included in Fraser [1999], 7 reported higher cesarean rates in the amniotomy group, 2 reported lower rates, and 1 small trial had no cesareans.)
• Routine amniotomy has no clinically significant neonatal benefits (Fraser, 1999).	Quality:	B a
	Quantity:	A
	Consistency:	A**
Routine amniotomy may increase the risk of nonreassuring fetal heart rate (FHR) (Fraser, 1993; Fraser, 1999, Garite, 1993; Mercer, 1995).	Quality:	B
	Quantity:	A
	Consistency:	B (Fraser [1999] did not find an increased incidence, but reviewers note that a reanalysis, taking into account that amniotomy shortened labor, did increase incidence. An increase in episodes of nonreassuring FHR is biologically plausible in that releasing the amniotic fluid increases pressure on the fetal head and umbilical cord during contractions.)
Early amniotomy may increase the maternal and neonatal infection rate (Fraser, 1999; Mercer, 1995; Rouse, 1994; Soper, 1996).	Quality:	B
	Quantity:	A
	Consistency:	B a (Fraser [1999], a SR, did not find an increased incidence, but other studies find a strong association between duration of ruptured membranes, time, and invasive procedures.)
Amniotomy can lead to umbilical cord prolapse (Roberts, 1997; Usta, 1999).	Quality:	A
	Quantity:	B
	Consistency:	A

A = good, B = fair, NEB = no evidence of benefit

Quality = aggregate of quality ratings for individual studies

Quantity = magnitude of effect, numbers of studies, and sample size or power

Consistency = the extent to which similar findings are reported using similar and different study designs

^*only 1 study

^**multiple studies in SR

^a

Randomized controlled trials (RCTs) of amniotomy and, hence, systematic reviews of those trials suffer from confounding factors that could affect labor progress, occurrence of adverse events (abnormal fetal heart rate, infection, cesarean section), or both, specifically:

• Substantial proportions of women in the control group, more than half in some cases, also had amniotomies.
• Women in the control group were more likely to have oxytocin (Fraser, 1999).
• Women had vaginal examinations after membrane rupture and, in some trials, internal monitoring in both arms of the trial.

In addition, trials included only women with full-term, uncomplicated pregnancies. This means that differences between groups might be wider than they appear. First, in studies where amniotomy appears to be harmless, this might not have been the case had not so many women in the control group had amniotomies or had the baby's ability to withstand stress been less than optimal. Second, where studies report harmful effects, the difference between amniotomy and control group might have been more pronounced.