This tool visualizes labor duration data from a 10-year cohort of 41,868 vaginal deliveries at a New York City tertiary center (2013–2022). Explore how BMI class affects latent phase, active phase, and total first-stage labor duration — stratified by parity and labor onset. Use the Labor Progress Estimator below to contextualize an individual patient's timeline against BMI-specific reference data.
Evidence Base — Source Publication
1
Primary Source · Cohort Study · AJOG 2026
Edwards SE, Cohen R, Zhao Z, Kishan R, Steelman M, Bianco A, McCarthy K, Glazer KB, DeBolt CA. Characterizing labor progression and duration according to maternal body mass index. Am J Obstet Gynecol. 2026;234:1148–1171. https://doi.org/10.1016/j.ajog.2025.11.003
N=41,868 vaginal deliveries (2013–2022) · Mount Sinai Health System, NYC · BMI classified per IOM guidelines · Interval-censored regression with log-normal distribution
Explorer Controls
Class III Obesity ⓘ
Labor Curves by BMI Category
Median time to reach each centimeter of cervical dilation
Latent phase: 0–6 cm |
Active phase: 6–10 cm
Each data point = median time (hours) to reach that dilation level (interval-censored regression, log-normal distribution). Source: Edwards et al., AJOG 2026.
Class III Obesity excluded from labor curves: Per-centimeter dilation data were not tabulated for Class III Obesity in Supplemental Table 1 of the source publication. Phase-total data (latent, active, total) for Class III are available in the bar chart and data tables below. Source: Edwards et al. AJOG 2026.
Dilation Over Median Time by BMI Category
All 5 BMI classes · All births · Partogram orientation: dilation on Y-axis, time on X-axis. Source: Edwards et al. AJOG 2026.
Subgroups:
Line styles:
Normal / Underweight
Overweight
Class I Obesity
Class II Obesity
Class III Obesity
Class III: only total first-stage endpoint plotted (per-cm data not tabulated in source). All other classes: full per-cm curves. Source: Edwards et al. AJOG 2026, Supp Table 1 & Table 2.
Labor Progress Estimator
Enter a patient's current dilation, hours in labor so far, and their BMI class. This tool contextualizes their progress against BMI-specific median reference data from the all-births cohort (N=41,868). This is a reference tool — not a clinical decision algorithm.
Full Data Table — Labor Phase Duration by BMI Class (All Births)
BMI Category
N
Latent Phase (h) [95% CI]
Active Phase (h) [95% CI]
Total 1st Stage (h) [95% CI]
Normal / Underweight
9,491
3.7 [3.6–3.8]
1.2 [1.1–1.3]
4.9 [4.8–5.0]
Overweight
19,658
4.3 [4.2–4.4]*
1.3 [1.2–1.4]
5.6 [5.5–5.7]*
Class I Obesity
8,880
5.0 [4.9–5.1]*
1.4 [1.3–1.6]†
6.4 [6.3–6.6]*
Class II Obesity
2,826
5.6 [5.4–5.9]*
1.5 [1.1–1.8]
7.1 [6.8–7.4]*
Class III Obesity
1,013
6.9 [6.4–7.5]*
1.6 [1.0–2.2]
8.5 [7.9–9.1]*
* p<0.01 vs normal weight/underweight † p<0.05 vs normal weight/underweight. Source: Edwards et al. AJOG 2026, Table 2.
Latent Phase by Parity and Labor Onset (Median hours, 95% CI)
Subgroup
Normal Wt.
Overweight
Class I OB
Class II OB
Class III OB
Nulliparous · Spontaneous
3.1 h
3.8 h
4.4 h
4.6 h
6.3 h
Nulliparous · Induced
8.7 h
9.3 h
10.1 h
10.4 h
11.9 h
Multiparous · Spontaneous
2.0 h
2.1 h
2.4 h
2.8 h
3.2 h
Multiparous · Induced
5.7 h
6.1 h
6.6 h
7.4 h
8.0 h
All differences statistically significant (p<0.01) vs. normal weight reference, except multiparous spontaneous overweight vs. normal (p=0.07). Source: Edwards et al. AJOG 2026, Table 2.
Labor Curves by Subgroup — Side-by-Side Comparison
All four parity × labor-onset subgroups shown simultaneously. BMI classes: Normal (blue), Overweight (green), Class I (amber), Class II (red). Source: Edwards et al. AJOG 2026, Supplemental Tables 2–5.
Show:Class III Obesity ⓘ
Nulliparous · Spontaneous Labor
N=13,333 | Supp Table 3
Nulliparous · Induced Labor
N=7,193 | Supp Table 2
Multiparous · Spontaneous Labor
N=14,654 | Supp Table 5
Multiparous · Induced Labor
N=6,688 | Supp Table 4
Normal / Underweight
Overweight
Class I Obesity
Class II Obesity
Vertical dashed line marks transition from latent (0–6 cm) to active phase (6–10 cm). Class III excluded: per-cm data not tabulated in source. Source: Edwards et al. AJOG 2026.
Custom Overlay — Compare Any Subgroups
Tick any combination of the 4 subgroups and up to 4 BMI classes. All selections plot together on one chart. Color = BMI class · Line style = subgroup. Source: Edwards et al. AJOG 2026, Supp Tables 2–5.
① Select subgroups (any combination)
② Select BMI classes (any combination)
Class III Obesity ⓘ
Line styles:Nulli · SpontNulli · InducedMulti · SpontMulti · Induced· Color = BMI class
Vertical gray line = latent→active boundary (6 cm). Class III excluded: per-cm data not tabulated in source. Source: Edwards et al. AJOG 2026.
Key Clinical Takeaways
Latent phase drives the difference
Latent phase duration increased monotonically with BMI class (3.7 h → 6.9 h). Active phase did not differ significantly across BMI groups (1.2–1.6 h).
Nearly 2× longer total labor (Class III)
Median first-stage duration was 8.5 h in Class III obesity vs. 4.9 h in normal weight — the same doubling pattern across parity and labor onset subgroups.
BMI-specific curves may reduce unnecessary CS
Applying standard labor curves to patients with obesity may misclassify normal (BMI-appropriate) latent-phase duration as labor arrest, potentially driving avoidable cesarean delivery.
Induced nulliparas with Class III obesity
Longest latent phase of any subgroup: 11.9 h [11.0–12.9] vs. 8.7 h [8.4–8.9] for normal weight. This 3.2-hour difference has direct implications for IOL timing and patience thresholds.
Source: Edwards SE et al. Am J Obstet Gynecol. 2026;234:1148–1171.