"Active Labor" Duration and Dilation Rates among Low-risk, Nulliparous Women with Spontaneous Labor Onset: A Systematic Review

Jeremy L. Neal, CNM, RNC, PhD; Nancy K. Lowe, CNM, PhD; Karen L. Ahijevych, RN, PhD; Thelma E. Patrick, RN, PhD; Lori A. Cabbage, CNM, FNP, MSN; Elizabeth J. Corwin, RN, PhD

Disclosures

J Midwifery Womens Health

Abstract and Introduction

Abstract

Introduction: Laboring women are often admitted to labor units under criteria that are commonly associated with the onset of active-phase labor (i.e., cervical dilatation of 3–5 cm in the presence of regular contractions). Beginning with these criteria through complete dilatation, this systematic review describes labor duration and cervical dilation rates among low-risk, nulliparous women with spontaneous labor onset.
Methods: Studies published in English (between 1990 and 2008) were identified via MEDLINE and CINAHL searches. Data were abstracted and weighted "active labor" durations (i.e., from 3–5 cm through complete dilatation) and linear dilation rates were calculated.
Results: Eighteen studies (n = 7009) reported mean "active labor" duration. The weighted mean duration was 6.0 hours, and the calculated dilation rate was 1.2 cm per hour. These findings closely parallel those found at the median. At the statistical limits, the weighted "active labor" duration was 13.4 hours (mean + 2 standard deviations) and the dilation rate was 0.6 cm per hour (mean – 2 standard deviations).
Discussion: These findings indicate that nulliparous women with spontaneous labor onset have longer "active" labors and therefore slower dilation rates than are traditionally associated with active labor when commonly used criteria are applied as the starting point. Revision of existing active labor expectations and/or criteria used to prospectively identify active phase onset is warranted.

Introduction

Labor is "the presence of uterine contractions of sufficient frequency, duration, and intensity to cause demonstrable effacement and dilation of the cervix."^[1] Attempts to define the norms and limits of labor duration have yielded variable results, undoubtedly because labor does not readily lend itself to measurement. Not only is prospectively defining the onset of labor a significant challenge, but evaluating its progression remains limited to rudimentary cervical examinations performed episodically. Attempts to divide the continuum of labor into stages and phases only add to the complexity. Moreover, multiple fixed factors such as parity, maternal weight, and fetal weight as well as commonly employed interventions (e.g., oxytocin augmentation and epidural use) may significantly affect the duration of labor.

In spite of measurement difficulties, a better understanding of the norms and slowest acceptable limits of labor duration and rates of cervical dilation is important because this knowledge is the backbone of clinical decision-making in the intrapartum setting. Optimally defining these indices from the point of typical spontaneous labor admission forward is especially pertinent because, once admitted to the hospital, women are closely monitored to ensure adequate progress. Therefore, the purpose of this systematic review was to describe the clinical parameters of "active labor" duration and rates of cervical dilation beginning with clinical criteria commonly used as prospective evidence of the onset of active-phase labor through complete cervical dilatation. The focus is on nulliparous women without chronic medical conditions or pregnancy complications who were admitted for spontaneous labor onset.

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Abstract and Introduction
Background
Methods
Results
Discussion
Conclusion
References

Table 1. The 25 Studies Included in this Systematic Review
Trial, Location, Date	N	Trial Type	Inclusion/Exclusion Criteria^a	Qualifying Groups/Subgroups
Fraser et al., Canada and US, 1993^[22]	925	Prospective, randomized	Inclusion: Intact membranes; normal fetal heart rate Exclusion: Suspected IUGR; severe preeclampsia; IDDM; ≥6 cm at admission; maternal distress too great to permit informed consent	Routine early amniotomy vs. conservative membrane management after admission at ≥3 cm^e
Cammu et al., Belgium, 1994^[23]	110	Prospective, randomized	Inclusion: Low-risk; 3–5 cm at admission; ruptured membranes with clear fluid; no dystocia at inclusion	Bathing vs. nonbathing with AML
Cammu et al., Belgium, 1994^[24]	1000	Prospective, observational	Inclusion: No contraindications for labor; maternal height ≥150 cm; ≥ 1 antenatal care visit(s)	Unaugmented vs. augmented labor with AML but without epidural^e
Albers et al., US, 1996^[15]	347^b	Retrospective, record review	Inclusion: Low-risk; non-Hispanic white, Hispanic, or American Indian; ≤4 cm at admission (for active phase analyses) Exclusion: Medical problems (e.g., hypertension, gestational diabetes, asthma, or membranes ruptured >24 hrs); oxytocin augmentation; epidural analgesia; operative delivery	No treatment
Cammu and Van Eeckhout, Belgium, 1996^[25]	306	Prospective, randomized	Inclusion: Normal cardiotocogram and clear amniotic fluid at admission; maternal height ≥150 cm; ≥ 1 antenatal outpatient clinic visit(s)	AML vs. selective intervention
Bofill et al., US, 1997^[26]	100	Prospective, randomized	Inclusion: Healthy Exclusion: Medical problems (e.g., IDDM, medicated chronic hypertension, or PIH)	Epidural vs. narcotics for labor pain relief
Dickinson et al., Australia, 1997^[18]	497	Prospective, observational	Inclusion: Low-risk	Epidural vs. nonepidural with modified AML
Alexander et al., US, 1998^[27]	199	Retrospective analysis of randomized trial	Inclusion: Normal pregnancy; augmented with oxytocin; nonoperative vaginal delivery Exclusion: Pregnancy complication; >5 cm at admission	Epidural vs. IV meperidine for labor pain relief
Clark et al., US, 1998^[28]	318	Prospective, randomized	Exclusion: Contraindication to labor; thrombocytopenia or coagulation disorder precluding epidural placement	Epidural vs. IV meperidine during AML for labor pain relief
Thompson et al., US, 1998^[29]	641	Retrospective, chart review	Inclusion: Low-risk; 18–35 yrs old; prenatal care provided by study institution; black or white Exclusion: Drug or alcohol abuse; smoking; preeclampsia; hypertension; diabetes; ≥7 cm at admission; prepregnancy weight >100 kg; chronic medical condition; history of pelvic injury or major abdominal surgery; hospitalization during pregnancy; uterine myoma; active genital herpes; oligo- or polyhydramnios; incomplete medical record	No epidural (no analgesia or parenteral opioids only) vs. low-dose epidural vs. high-dose epidural
Albers, US, 1999^[16]	806^b	Prospective, observational	Inclusion: Low-risk; ≤4 cm at admission; membranes ruptured <24 hrs Exclusion: Medical problems (hypertension, gestational diabetes, asthma, or drug use); oxytocin augmentation; epidural analgesia; operative delivery (cesarean, forceps, or vacuum)	No treatment
Fontaine and Adam, US, 2000^[30]	100^b	Retrospective, chart review	Inclusion: < 6 cm at admission Exclusion: Epidural use; other undefined reasons	ITN vs. no ITN (IV narcotics or no analgesia)
Garite et al., US, 2000^[31]	195	Prospective, randomized	Inclusion: Uncomplicated pregnancy; 2–5 cm with or without ruptured membranes Exclusion: Preeclampsia; cardiac or renal disease; chorioamnionitis, pyelonephritis, or febrile illness before randomization	Isotonic IV fluids at 125 mL/hr vs. 250 mL/hr during labor
Sadler et al., New Zealand, 2000^[32]	651	Prospective, randomized	Exclusion: Evidence of fetal distress at admission; severe cardiac disease; uterine scar; contracted pelvis; elective cesarean	AML vs. routine labor management
Sharma et al., India, 2001^[33]	150	Prospective, randomized	Inclusion: Healthy; 18–30 yrs old; intact membranes; dilatation of 4 cm with partially effaced cervix; established contractions Exclusion: Medical, surgical, or obstetric complications (e.g., preeclampsia or antepartum hemorrhage); dilatation >5 cm	IM drotaverine hydrochloride vs. IM valethamate bromide vs. unmedicated group
Zhang et al., US, 2001^[34]	1088	Retrospective, chart review	Inclusion: < 7 cm at admission; admission to delivery duration ≥3 hrs; 18–34 yrs old; birth weight of 2.5–4 kg	Before vs. after "on-demand" epidural analgesia
Gurewitsch et al., US and Israel, 2002^[35]	908^b	Retrospective, comparative	Inclusion: Uncomplicated pregnancy; ≥3 first-stage cervical examinations Exclusion: Contraindication to labor; uterine scars; hydramnios; fetal anomaly	No treatment
Jones and Larson, US, 2003^[17]	120^b	Retrospective, comparative	Inclusion: Hispanic; 15–44 yrs old; spontaneous vaginal birth Exclusion: Cephalopelvic disproportion; prolonged membrane rupture; social or medical problems (substance abuse, hypertension, diabetes, or asthma); oxytocin augmentation; regional anesthesia	No treatment
Kaul et al., US, 2004^[36]	1671	Retrospective, comparative	Inclusion: Healthy; epidural during labor; oxytocin augmentation during labor as subgroup; elective IOL as subgroup Exclusion: Previous medical problems; complicated pregnancy; cesareans for fetal distress	Oxytocin augmentation group^e
Somprasit et al., Thailand, 2005^[37]	960	Prospective, randomized	Inclusion: Low-risk Exclusion: Medical or surgical complications; contraindications to vaginal delivery or oxytocin use; fetal distress at admission; diabetes; PIH	AML vs. conventional labor management
Vahratian et al., US, 2005^[38]	2200	Retrospective, chart review	Inclusion: Low-risk; elective IOL as subgroup Exclusion: Diabetes; hypertension; previous infectious cardiovascular, pulmonary, renal, mental, or thyroid disorders; IUGR; uterine bleeding; oligohydramnios	Spontaneous labor onset group^e
Eslamian et al., Iran, 2006^[19]	300	Prospective, randomized	Inclusion: Uncomplicated pregnancy; 3–5 cm; intact membranes Exclusion: Chorioamnionitis; febrile illness or pyelonephritis; preeclampsia; history of cardiac or renal disease	Isotonic IV fluids at 125 mL/hr vs. 250 mL/hr during labor
Mikki et al., Israel, 2007^[39]	157^b	Prospective, randomized	Inclusion: Low-risk; intact membranes at admission; normal fetal heart rate Exclusion: Advanced labor; IUGR; suspected macrosomia (>4.5 kg); preeclampsia; IDDM; antepartum hemorrhage	Early amniotomy vs. intent to conserve membranes
Miquelutti et al., Brazil, 2007^[20]	107	Prospective, randomized	Inclusion: ^c Low-risk; 3–5 cm at admission; 16–40 yrs old Exclusion: Elective cesarean; contraindications to upright positions	Upright position vs. no particular position encouraged (control group)
Svärdby et al., Sweden, 2007^[21]	164	Prospective, observational	Inclusion: ^d Uncomplicated pregnancy	No augmentation vs. active phase vs. second-stage augmentation

AML = Active management of labor; IDDM = insulin-dependent diabetes mellitus; IM = intramuscular; IOL = induction of labor; ITN = intrathecally-injected narcotics; IUGR = intrauterine growth restriction; IV = intravenous; PIH = pregnancy-induced hypertension.
^aAll studies included nulliparae carrying live, singleton, cephalic presenting fetuses at a minimum of 36 weeks' gestation with spontaneous labor onset. Mean, median, or absolute dilatation between 3 and 5 cm at study enrollment or randomization must have been identified.
^bValue represents nulliparous women only, although this study also included primiparous and/or multiparous groups/subgroups.
^cThrough contact with author, it was clarified that all labors had a spontaneous onset.
^dThrough contact with author, it was clarified that "primigravid" rather than "primiparous" women were included in the study.
^eStudy also included nulliparous subgroup(s) not qualifying for systematic review because dilatation at "active" phase onset was <3 cm, unknown, or labor was induced.

Table 2. Eighteen Studies With Mean Measures of "Active Phase" Duration in this Systematic Review
Trial, Year	Group/Subgroup	n	Dilatation at "Active Phase" Onset (cm)^a	"Active Phase" Duration (hrs)		Rate of "Active Phase" Dilation (cm/hr)^c
Trial, Year	Group/Subgroup	n	Dilatation at "Active Phase" Onset (cm)^a	Mean (SD)	Mean + 2 SD	Mean	Limit
Cammu et al., 1994^[23]	Bathing group	54	3.8 (0.9)	4.07 (2.32)	8.71	1.5	0.7
Cammu et al., 1994^[23]	Nonbathing group	56	4.0 (1.0)	4.4 (2.83)	10.06	1.4	0.6
Cammu et al., 1994^[24]	Unaugmented labor, no epidural	477	3.7 (1.6)	2.53 (1.3)	5.13	2.5	1.2
Cammu et al., 1994^[24]	Augmented labor, no epidural	159	3.1 (1.2)	4.73 (1.75)	8.23	1.5	0.8
Albers et al., 1996^[15]	No treatment	347	4	7.7 (5.9)	19.4	0.8	0.3
Cammu and Van Eeckhout, 1996^[25]	AML group	152	3.2 (1.1)	4.23 (2.35)	8.93	1.6	0.8
Cammu and Van Eeckhout, 1996^[25]	Selective intervention group	154	3.2 (1.1)	4.72 (2.57)	9.86	1.4	0.7
Bofill et al., 1997^[26]	Epidural analgesia	49	4.2 (1.0)	6.25 (2.38)	11.01	0.9	0.5
Bofill et al., 1997^[26]	Narcotics	51	4.2 (0.9)	5.95 (2.55)	11.05	1.0	0.5
Alexander et al., 1998^[27]	Epidural group	126	4	7.9 (3.0)	13.9	0.8	0.4
Alexander et al., 1998^[27]	IV meperidine group	73	4	6.3 (3.0)	12.3	1.0	0.5
Clark et al., 1998^[28]	Epidural group	156	4	5.18 (2.7)	10.58	1.2	0.6
Clark et al., 1998^[28]	IV meperidine group	162	4	4.57 (2.35)	9.27	1.3	0.7
Thompson et al., 1998^[29]	No epidural (with labor curve)	142	4	5.25^d	—	1.1	—
	Low-dose epidural (with labor curve)	172	4	6.0^d	—	1.0	—
	High-dose epidural (with labor curve)	72	4	6.5^d	—	0.9	—
Albers, 1999^[16]	No treatment	806	4	7.7 (4.9)	17.5	0.8	0.3
Fontaine and Adams, 2000^[30]	ITN	50	4	5.17 (—)	—	1.2	—
Fontaine and Adams, 2000^[30]	No ITN	50	4	4.43 (—)	—	1.4	—
Garite et al., 2000^[31]	IV fluids at 125 mL/hr (vaginal delivery)	78	3.6 (—)	8.05 (—)	—	0.8	—
Garite et al., 2000^[31]	IV fluids at 250 mL/hr (vaginal delivery)	91	3.8 (—)	6.88 (—)	—	0.9	—
Sharma et al., 2001^[33]	IM drotaverine HCL group	50	4	2.94^e	—	2.0	—
	IM valethamate bromide group	50	4	3.21^e	—	1.9	—
	Unmedicated group	50	4	5.94^e	—	1.0	—
Gurewitsch et al., 2002^[35]	No treatment	908	3.1 (1.5)	4.5^d	—	1.5	—
Jones et al., 2003^[17]	No treatment	120	4	6.2 (3.6)	13.4	1.0	0.5
Kaul et al., 2004^[36]	Oxytocin augmentation group	996	4 [3, 4]	5.3	—	1.1	—
Somprasit et al., 2005^[37]	AML group	320	3.1 (1.2)	8.97 (4.05)	17.07	0.8	0.4
Somprasit et al., 2005^[37]	Conventional labor management group	640	3.1 (1.4)	9.82 (4.4)	18.62	0.7	0.4
Eslamian et al., 2006^[19]	IV fluids at 125 mL/hr (vaginal delivery)	118	4^b	6.12 (1.75)	9.62	1.0	0.6
Eslamian et al., 2006^[19]	IV fluids at 250 mL/hr (vaginal delivery)	123	4^b	3.93 (1.43)	6.79	1.5	0.9
Mikki et al., 2007^[39]	Early amniotomy	74	3 [3, 4]	3.85 (1.83)	7.51	1.8	0.9
Mikki et al., 2007^[39]	Intent to conserve membranes	83	4 [3, 4]	5.28 (2.27)	9.82	1.1	0.6
Weighted values		7009	3.7 (0.4)	6.0 (2.0)	13.4 (5.0)	1.2 (0.5)	0.6 (0.3)

AML = Active management of labor; HCL = hydrochloride, IM = intramuscular; ITN = intrathecally-injected narcotics; IV = intravenous; IQR = interquartile range; SD = standard deviation.
^aGroup mean (SD), median [IQR], or absolute value shown when provided in study.
^bThrough contact with author, it was clarified that median dilatation was 4 cm at "active phase" onset.
^cCalculated based on assumption that the cervical dilation phase ends at 10 cm, which approximates complete cervical dilatation.
^dValue derived from graphical labor curve presented in study publication.
^eCalculated based on mean rate of dilation provided in study publication.

Table 3. Eight Studies With Median Measures of "Active Phase" Duration in this Systematic Review
Trial, Year	Treatment	n	Dilatation at "Active Phase" Onset (cm)^a	Median Duration (hrs)	Rate of "Active Phase" Dilation (cm/hr)^b
Fraser et al., 1993^[22]	Routine early amniotomy	390	3.8 (0.9)	4.33	1.4
Fraser et al., 1993^[22]	Conservative membrane management	383	3.8 (0.8)	6.42	1.0
Dickinson et al., 1997^[18]	Epidural analgesia group	257	4^c	4.6	1.3
Dickinson et al., 1997^[18]	Nonepidural group	240	4^c	2.75	2.2
Sadler et al., 2000^[32]	AML group (vaginal delivery)	290	4.5 (1.8)	4.0	1.4
Sadler et al., 2000^[32]	Routine management (vaginal delivery)	299	4.5 (2.1)	4.83	1.1
Zhang et al., 2001^[34]	Before "on-demand" epidural analgesia	507	4	6.0	1.0
Zhang et al., 2001^[34]	After "on-demand" epidural analgesia	581	4	6.0	1.0
Vahratian et al., 2005^[38]	Spontaneous onset of labor group	1171	4	5.97	1.0
Mikki et al., 2007^[39]	Early amniotomy	74	3 [3,4]	3.5	2.0
Mikki et al., 2007^[39]	Intent to conserve membranes	83	4 [3,4]	5.0	1.2
Miquelutti et al., 2007^[20]	Upright position group	35	4^c	6.5	0.9
Miquelutti et al., 2007^[20]	Control group	42	4^c	5.42	1.1
Svärdby et al., 2007^[21]	No augmentation	50	4^c	5.08	1.2
	Active phase augmentation	88	4^c	7.32	0.8
	Second stage augmentation	26	4^c	7.33	0.8
Weighted values		4516	4.0 (0.2)	5.4 (1.0)	1.2 (0.3)

AML = Active management of labor.
^aGroup mean (SD), median [IQR], or absolute value shown when provided in study.
^bCalculated based on assumption that the cervical dilation phase ends at 10 cm, which approximates complete cervical dilatation.
^cThrough contact with author, it was clarified that active phase onset was defined as 4 cm dilatation.

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