First stage of labor

1. When does active labor start?

In Friedman’s original articles a specific cervical dilation was not identified as active labor. In his 1978 text Labor: Clinical evaluation and management Dr. Emanual Friedman demarcated active labor as the inflection point on the labor curve where the rate of cervical dilation was 1.2 cm hr⁻¹ in nulliparous patients and 1.5 cm hr⁻¹ in multiparous patients. This inflection point is depicted at 4 cm. Four cm has been accepted as the entry point to active labor until data from the CSL was analyzed. “Nulliparous and multiparous women appeared to progress at a similar pace before six cm. However, after six cm, labor accelerated much faster in multiparous than in nulliparous women.” [4]. The inflection point in the CSL labor curves occurred around six cm, moving the start of active labor to 6 cm (Figures 53.1a and b).

1. 2. How long could it take my patient to progress from 4 cm to 6 cm? 6 cm to 10 cm?

According to CSL data, labor may take up to 6.4 hours for a nulliparous women to progress from 4 to 5 cm and an additional 3.2 hours from 5 to 6 cm cervical dilation (95%). The median and 95 percentiles for cervical change before 6 cm for nulliparous and multiparas were close with no significant difference. The nulliparous patient can expect to spend from 2.1 to 8.6 hours in active labor whereas active labor in the multiparous patient lasts 1.5 to 7.5 hours (median to 95 percentiles) [4]. “Historical criteria defining normal labor progress‐cervical change of 1.2 cm hr⁻¹ for nulliparous women and 1.5 cm hr⁻¹ for multiparous women‐are no longer valid.” [6] (Figures 53.1a and b).

1. 3. How do I diagnosis active‐phase arrest?

The traditional diagnosis of arrest of the active‐phase was based on several premises:

• Active labor starts at 4 cm.
  
• Montevideo Units (MVUs) to assess the adequacy of uterine contractions.

The definition was based on the “two hour rule”. Lack of cervical change over two hours with adequate contractions, as defined by 200–220 MVU over a 10 minute period, equaled active‐phase arrest. In 2001 Rouse et al. challenged the “two hour rule”. A standard protocol was implemented to extend the time from two to four hours. A total of 61% of the patients that had arrested at two hours subsequently went on to have a vaginal delivery [7]. Evaluation of the data revealed more cesarean deliveries would have been performed than infections prevented if the “two hour rule” had been followed. For many this study and the follow‐up study by Rouse utilizing oxytocin augmentation for four hours prior to diagnosing active labor phase arrest created a point of practice change. [8] The “two hour rule” became the “four hour rule”. Additional modifications reflecting the changes noted in the Consortium for Safe Labor are presented in the Table 53.1 below:

1. 4. How does my patient’s age affect labor progress?

Most research has focused on maternal and neonatal outcomes related to maternal age. In 2007 Greenberg et al. published a retrospective cohort study to evaluate the length of labor across maternal age groups. The study utilized term nulliparous and multiparous women from 1980 to 2001 at a single California institution, amounting to 31 976 deliveries. Patients were divided into six age groups; under 20, 20–24, 25–29, 30–34, 35–39, and 40 and over. The researchers found that nulliparous women experienced significantly longer labors with increasing age. This effect was intensified if the patient received epidural analgesia. The effect was most pronounced in the 35–39 y/o age group (Table 53.2).

The CSL data was analyzed to answer the same question, with a different result. The CSL data included 120 442 deliveries across 19 institutions from 2002 to 2008. Patients were grouped by parity (nulliparous/multiparous) and by age group (<20, 20–29, 30–39, ≥40). The trend was a shorter first stage of labor with increasing maternal age without reaching statistical significance [9] (Table 53.3).

1. 5. Does obesity affect labor progress?

Four retrospective cohort studies published over the last four years directly answer this question. Labor proceeds more slowly as the BMI increases.

Kominiarek et al. in 2011 analyzed data from the CSL utilizing 118 978 women stratified by BMI (<25, 25–29.9, 30–34.9, 35–39.9 ≥ 40) and parity. The median and 95 percentile duration from 4 to 10 cm were significantly longer in the obese patients for both nulliparous and multiparous women [10]. As shown in Table 53.4.

Hillard et al. and Norman et al. reached similar conclusions of the dose related effect of obesity on the duration of the first stage of labor [11, 12]. Our Swedish colleagues Carlhäll, Källénd, and Blomberg analyzed delivery data gathered through a Swedish regional perinatal database collected from 1995 to 2009 of 63 829 nulliparous women who presented in spontaneous labor. The retrospective cohort study compared women by BMI and duration of labor. Again increasing duration of labor was demonstrated with increasing BMI. The largest difference was noted between BMI <18.5 and BMI >40 with a p value <0.001. Although statistical significance was reached with all classes of obesity in comparison to normal weight parturients [13].

Second stage of labor

1. What is meant by passive or active second stage?

Second stage of labor begins at complete dilation and ends at delivery of the newborn. Passive second stage refers to the absence of maternal expulsive efforts and is often referred to as “laboring down”. The intention is to allow the fetus to passively move further down the birth canal via the expulsive forces of the uterus prior to starting the active portion of the second stage. Active second stage indicates the period of time of maternal expulsive efforts.

As part of a 2008–2011 NICHD Maternal‐Fetal Medicine Units Network, Yee et al. completed a secondary analysis of the initial 115 502 cohort comparing early with delayed pushing among nulliparous women. 21 034 women were included in the final comparison. Delayed pushing resulted in; a longer second stage with a longer active stage, increased cesarean section rate, increased operative vaginal delivery rate, along with an increased rate of PPH and transfusion [14] (Table 53.5).

A 2015 Cochrane Database review looked at the question of immediate versus delayed pushing. All patients studied had received epidurals. Delaying pushing extended the duration of the second stage by 54 minutes, but decreased the active portion by 22 minutes and increased the rate of vaginal delivery 61.5% versus 56.9% (RR1.09, 95% CI 1.03–1.15). The delayed group had an increased risk of low umbilical artery pH without a difference in neonatal intensive care unit (NICU) admissions. Also evaluated was spontaneous versus directed pushing. There was no significant outcome differences between the two groups in duration, maternal or neonatal complications. In summary delayed versus immediate, spontaneous versus directed show no significant benefit [15].

1. 2. Is there a wrong way to push?

The classically propagated maternal expulsive technique involves Valsalva or closed glottis pushing. Across many labor floors you can hear the refrains of one… two… three… and so on as women are coached to hold their breath and bear down to the count of ten. As the standard across the nation and even across the pond there is surprisingly little research to back up the practice. Prins et al. published the best review to date and described the current literature supporting Valsalva pushing as “sparse, and flawed”. Furthermore there appears to be no benefit for maternal or neonatal outcome for either Valsalva or physiologic (open glottis) pushing techniques. The researchers final recommendations were for further investigations and for the current time “women should be supported in following the feelings of their bodies and use their own bearing down efforts and urges to push.” [16].

1. 3. What effect does maternal position have on the second stage?

A 2012 Cochrane Database Review, “Position in the Second Stage of Labor for Women without Epidural Anesthesia” evaluated 22 studies, 7280 women. The review found most studies were of poor methodological quality with inconsistent clinical interventions. A meta‐analysis comparing upright or lateral position versus supine or lithotomy concluded supine position was associated with fewer spontaneous births and more non‐reassuring fetal heart rate tracings. The abnormal fetal heart tracings are likely the result of aorto‐caval compression. Upright positions were associated with higher rates of blood loss >500 ml (RR 1.65, 95% CI 1.32–2.06) and a shorter but not statistically significant duration of the second stage of labor. [17]. From this review one may infer that the lateral position or supine with lateral uterine displacement maybe advantageous, but until more trials are conducted women should elect the position of their choice.

A similar Cochrane Database Review in 2013 evaluated women with epidural anesthesia. In five randomized controlled trials involving 879 women all with epidural anesthesia identified no statistically significant difference between upright and recumbent positions with regards to operative abdominal or vaginal deliveries. Two trials incorporating 322 women showed no significant difference in duration of second stage of labor. Due to the wide confidence intervals and the insufficient data no conclusions can be made with regards to the effect of maternal position with epidural anesthesia present. [18].

The Italian research team, Gizzo S, Di Gangi S, Novena M, Bacile V, Zambon A, and Battista Nardelli G, of the University of Padua conducted an observational cohort study on nulliparous women divided into two groups. Group A patients spent ≥50% of their labor in the supine or lateral positions whereas Group B patients used alternate positions (sitting, squatting, standing, “on all fours”, sitting on the ball). Duration of second stage, analgesia request and presence of persistent occiput posterior were all increased with Group A (supine/lateral) with statistical significance (p values <0.001) [19] (Table 53.6).

1. 4. If the second stage extends beyond the ACOG parameters what are the chances for a vaginal delivery versus an operative delivery?

For the nulliparous patient traditional ACOG guidelines recommend a two hour second stage which can be extended to three hours if an epidural is in place. And with a multiparous patient one hour without an epidural and two hours with an epidural. The adoption and implementation of these guidelines extend back to times when the obstetrical population differed and when the operative vaginal delivery rate greatly exceeded both the epidural rate and the cesarean rate [1]. Today’s nulliparous patient has an 80% chance of receiving and epidural and at least a 50% of receiving oxytocin during labor [4].

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