The Association between Cervical Length and Successful Labor Induction: A Retrospective Cohort Study
Abstract
:1. Introduction
2. Materials and Methods
2.1. Study Design
2.2. Inclusion and Exclusion Criteria
2.3. Induction Protocol
2.4. Outcome Measurement
2.5. Primary Outcome
2.6. Other Characteristics Collected from the Patient
2.7. Statistical Analysis
3. Results
3.1. Demographics
3.2. Factors Associated with Successful Induction
3.3. The Percentage of Successful Labor Induction in Different Cervical Lengths
3.4. Factors Associated with Total Labor Time
3.5. ROC Curves of Cervical Length and Successful Induction
4. Discussion
Strengths and Limitations
5. Conclusions
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Acknowledgments
Conflicts of Interest
Glossary
Induction of labor | The use of medications or other methods to bring on labor |
Chi-squared test | Comparison of the distribution of categorial variables in different groups |
Fisher’s exact test | Analysis of contingency tables |
ROC (receiver operating characteristic) curve | A graph showing the performance of a classification model at all classification thresholds |
Independent t-test | An inferential statistical test that determines whether there is a statistically significant difference between the means in two unrelated groups |
Mann–Whitney U test | A test used to compare the differences between two independent groups that are either ordinal or continuous, but not normally distributed |
Bishop score | This system evaluates cervical condition including dilation, position of the cervix, effacement, station, and cervical consistence. Scores range from 0 to 3. With a Bishop score equal or more than 8, the chance of successful labor induction is favorable. |
Term pregnancy | A pregnancy gestation age equal or more than 37 weeks |
IUGR (intrauterine growth restriction) | Fetal weight is estimated to be below the 10th percentile for its gestational age |
Oligohydramnios | Amniotic fluid volume less than the minimum expected for gestational age |
Gestational hypertension/Preeclampsia | These are hypertensive disorders induced by pregnancy. Both disorders resolve postpartum. |
Polyhydramnios | Pathological increase of amniotic fluid volume in pregnancy |
Funneling | Ultrasound revealing a protrusion of amniotic membranes into the internal cervical os by greater than 5 mm from the shoulder of the original internal os |
Nulliparity | Women who have never have given birth to a child or who have never carried a pregnancy |
Multiparity | Parity ≧ 2 deliveries |
Cervical length | The linear distance from the internal os to the external os of the cervix measured by ultrasound |
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Successful Induction | Total | p-Value | ||
---|---|---|---|---|
No | Yes | |||
N (%) | 18 (13.1%) | 120 (86.9%) | 138 | |
Age (years) | 31.56 ± 5.74 | 29.98 ± 5.48 | 30.19 ± 5.52 | 0.262 |
Weight (kg) | 77.52 ± 15.05 | 74.20 ± 9.77 | 74.63 ± 10.60 | 0.216 |
BMI (kg/m2) | 30.92 ± 5.15 | 28.74 ± 3.93 | 29.02 ± 4.16 | 0.037 * |
GA (weeks) | 38.75 ± 0.73 | 39.05 ± 0.87 | 39.01 ± 0.85 | 0.174 |
GA group (weeks) | 0.790 | |||
37 + 0~37 + 6 | 2 (11.1%) | 8 (6.7%) | 10 (7.2%) | |
38 + 0~38 + 6 | 9 (50%) | 49 (40.8%) | 58 (42.0%) | |
39 + 0~39 + 6 | 5 (27.8%) | 44 (36.7%) | 49 (35.5%) | |
40 + 0~40 + 6 | 2 (11.1%) | 17 (14.2%) | 19 (13.8%) | |
41 + 0~41 + 6 | 0 (0%) | 2 (1.7%) | 2 (1.4%) | |
Hb (g/dL) | 11.27 ± 1.39 | 10.93 ± 1.54 | 10.97 ± 1.52 | 0.370 |
Parity [n (%)] | - | - | - | 0.004 * |
Nulliparity | 16 (88.9%) | 63 (52.5%) | 79 (57.2%) | |
Multiparity | 2 (11.1%) | 57 (47.5%) | 59 (42.8%) | |
Maternal disease [n (%)] | - | - | - | |
Normal | 14 (77.8%) | 90 (75.0%) | 104 (75.4%) | 1.000 |
IDA | 1 (5.6%) | 20 (16.7) | 21 (15.2%) | 0.308 |
Autoimmune disease | 0 (0.0%) | 3 (2.5%) | 3 (2.2%) | 1.000 |
Asthma | 1 (5.6%) | 2 (1.7%) | 3 (2.2%) | 0.345 |
Vitamin D deficiency | 0 (0.0%) | 2 (1.7%) | 2 (1.4%) | 1.000 |
Thyroid disease | 0 (0.0%) | 2 (1.7%) | 2 (1.4%) | 1.000 |
Cancer | 0 (0.0%) | 2 (1.7%) | 2 (1.4%) | 1.000 |
Thalassemia | 2 (11.1%) | 0 (0.0%) | 2 (1.4%) | 0.016 * |
HBV | 0 (0.0%) | 1 (0.8%) | 1 (0.7%) | 1.000 |
Sicca syndrome | 0 (0.0%) | 1 (0.8%) | 1 (0.7%) | 1.000 |
Prenatal problem [n (%)] | - | - | - | 0.055 |
Normal | 12 (66.7%) | 98 (81.7%) | 110 (79.7%) | |
GDM | 2 (11.1%) | 11 (9.2%) | 13 (9.4%) | |
IUGR | 1 (5.6%) | 5 (4.2%) | 6 (4.3%) | |
Gestational HTN | 0 (0.0%) | 2 (1.7%) | 2 (1.4%) | |
Polyhydramnios | 1 (5.6%) | 1 (0.8%) | 2 (1.4%) | |
Preeclampsia | 2 (11.1%) | 0 (0.0%) | 2 (1.4%) | |
SUA | 0 (0.0%) | 2 (1.7%) | 2 (1.4%) | |
Fetal arrhythmia | 0 (0.0%) | 1 (0.8%) | 1 (0.7%) | |
GBS (%) | 4 (22.2%) | 22 (18.3%) | 26 (18.8%) | 0.747 |
Indication of labor induction [n (%)] | - | - | - | 0.016 * |
No labor sign | 13 (72.2%) | 110 (91.7%) | 123 (89.1%) | |
IUGR | 1 (5.6%) | 5 (4.2%) | 6 (4.3%) | |
Oligohydramnios | 2 (11.1%) | 4 (3.3%) | 6 (4.3%) | |
Gestational HTN/Polyhydramnios/Preeclampsia | 2 (11.1%) | 1 (0.8%) | 3 (2.2%) | |
Induction method [n (%)] | - | - | - | 0.155 |
Prostin | 5 (27.8%) | 54 (45.0%) | 59 (42.8%) | |
Propess | 4 (22.2%) | 34 (28.3%) | 38 (27.5%) | |
Propess + Piton | 2 (11.1%) | 13 (10.8%) | 15 (10.9%) | |
Prostin + Piton | 3 (16.7%) | 9 (7.5%) | 12 (8.7%) | |
Propess + Prostin | 2 (11.1%) | 3 (2.5%) | 5 (3.6%) | |
Propess + Prostin + Piton | 2 (11.1%) | 7 (5.8%) | 9 (6.5%) | |
Epidural anesthesia [n (%)] | 11 (61.1%) | 86 (71.7%) | 97 (70.3%) | 0.361 |
Cervical length (cm) | 3.52 ± 0.65 | 2.84 ± 0.76 | 2.93 ± 0.78 | <0.001 * |
Cervical length group | <0.001 * | |||
<3.0 cm | 1 (5.6%) | 70 (58.3%) | 71 (51.4%) | |
3.0–3.5 cm | 8 (44.4%) | 26 (21.7%) | 34 (24.6%) | |
>3.5–4 cm | 5 (27.8%) | 18 (15.0%) | 23 (16.7%) | |
>4 cm | 4 (22.2%) | 6 (5.0%) | 10 (7.2%) | |
Funneling [n (%)] | 2 (11.1%) | 29 (24.2%) | 31 (22.5%) | 0.363 |
Bishop score | 2.00 ± 2.22 | 2.90 ± 2.21 | 2.78 ± 2.23 | 0.110 |
Position [n (%)] | - | - | - | 0.698 |
Posterior | 13 (72.2%) | 93 (77.5%) | 106 (76.8%) | |
Mid | 5 (27.8%) | 24 (20.0%) | 29 (21.0%) | |
Anterior | 0 (0.0%) | 3 (2.5%) | 3 (2.2%) | |
Dilation [n (%)] | - | - | - | 0.499 |
Closed | 14 (77.8%) | 79 (65.8%) | 93 (67.4%) | |
1–2 cm | 4 (22.2%) | 40 (33.3%) | 44 (31.9%) | |
3–4 cm | 0 (0.0%) | 1 (0.8%) | 1 (0.7%) | |
Effacement [n (%)] | - | - | - | 1.000 |
0–30% | 15 (83.3%) | 93 (77.5%) | 108 (78.3%) | |
40–50% | 3 (16.7%) | 23 (19.2%) | 26 (18.8%) | |
60–70% | 0 (0.0%) | 4 (3.3%) | 4 (2.9%) | |
Consistency [n (%)] | - | - | - | 0.127 |
Firm | 10 (55.6%) | 36 (30.0%) | 46 (33.3%) | |
Medium | 0 (0.0%) | 1 (0.8%) | 1 (0.7%) | |
Soft | 8 (44.4%) | 83 (69.2%) | 91 (65.9%) | |
Station [n (%)] | - | - | - | 0.683 |
−3 | 9 (50.0%) | 47 (39.2%) | 56(40.6%) | |
−2 | 8 (44.4%) | 65 (54.2%) | 73(52.9%) | |
−1, 0 | 1 (5.6%) | 8 (6.7%) | 9(6.5%) | |
Induction time (min) | 5194.50 ± 446.18 | 1132.23 ± 800.95 | 1198.82 ± 949.13 | <0.001 * |
Stages of labor (min) | - | - | - | |
1st stage | 1150.50 ± 1448.86 | 325.17 ± 404.26 | 338.70 ± 434.91 | 0.007 * |
2nd stage | 54.50 ± 21.92 | 78.35 ± 112.95 | 77.96 ± 112.07 | 0.767 |
3rd stage | 9.00 ± 2.83 | 4.71 ± 5.43 | 4.78 ± 5.42 | 0.268 |
Delivery mode [n (%)] | - | - | - | <0.001 * |
NSD | 1 (5.6%) | 85 (70.8%) | 86 (62.3%) | |
VED | 1 (5.6%) | 35 (29.2%) | 36 (26.1%) | |
C/S | 16 (88.9%) | 0 (0.0%) | 16 (11.6%) | |
Birth weight (g) | 3115.61 ± 348.53 | 3130.88 ± 327.08 | 3128.88 ± 328.67 | 0.855 |
Sex of fetus [n (%)] | - | - | - | 0.643 |
Female | 9 (50.0%) | 67 (55.8%) | 76 (55.1%) | |
Male | 9 (50.0%) | 53 (44.2%) | 62 (44.9%) |
Crude | Adjusted | |||
---|---|---|---|---|
Odds Ratio (95% CI) | p-Value | Odds Ratio (95% CI) | p-Value | |
Age (years) | 0.95 (0.86, 1.04) | 0.262 | 0.94 (0.84, 1.06) | 0.320 |
BMI (kg/m2) | 0.89 (0.79, 0.99) | 0.042 * | 0.87 (0.75, 0.99) | 0.044 * |
GA (weeks) | 1.53 (0.83, 2.83) | 0.174 | 2.13 (0.95, 4.78) | 0.066 |
Bishop score | 1.22 (0.95, 1.56) | 0.114 | 0.92 (0.69, 1.23) | 0.878 |
Cervical length | - | - | - | - |
>3.415 cm | Reference (1.0) | Reference (1.0) | ||
≤3.415 cm | 5.41 (1.91, 15.31) | 0.001 * | 6.22 (1.75, 22.15) | 0.005 * |
Parity | - | - | - | - |
Nulliparity | References | References | ||
Multiparity | 7.24 (1.59, 32.86) | 0.010 * | 17.69 (2.94, 106.51) | 0.002 * |
Fetal birth weight (kg) | 1.15 (0.26, 5.15) | 0.854 | 0.63 (0.10, 4.03) | 0.629 |
N | Successful Induction | p-Value | ||
---|---|---|---|---|
No | Yes | |||
Cervical length group | <0.001 * | |||
<3.0 cm | 71 | 1 (1.4%) | 70 (98.6%) | |
3.0–3.5 cm | 34 | 8 (23.5%) | 26 (76.5%) | |
>3.5–4.0 cm | 23 | 5 (21.7%) | 18 (78.3%) | |
>4 cm | 10 | 4 (40.0%) | 6 (60.0%) | |
Total | 138 | 18 (13.0%) | 120 (87.0%) |
Crude | Adjusted | |||||
---|---|---|---|---|---|---|
Regression Coefficient | 95% CI | p-Value | Regression Coefficient | 95% CI | p-Value | |
Age (years) | 10.92 | (−20.52, 42.36) | 0.493 | 8.68 | (−18.98, 36.35) | 0.535 |
BMI (kg/m2) | 6.50 | (−36.81, 49.80) | 0.767 | 21.61 | (−15.31, 58.53) | 0.249 |
GA (weeks) | 41.18 | (−158.52, 240.89) | 0.684 | −26.55 | (−210.92, 157.83) | 0.776 |
Bishop score | −114.41 | (−189.13, −39.69) | 0.003 * | −50.10 | (−121.74, 21.55) | 0.169 |
Cervical length (cm) | 300.82 | (84.26, 517.38) | 0.007 * | 301.87 | (92.82, 510.92) | 0.005 * |
Parity | - | - | - | - | - | - |
Nulliparity | Reference | Reference | NA | Reference | Reference | NA |
Multiparity | −873.95 | (−1177.76, −570.13) | <0.001 * | −947.74 | (−1256.94, −638.53) | <0.001 * |
Fetal birth weight (kg) | 47.26 | (-479.98, 574.50) | 0.859 | 231.55 | (−220.45, 683.54) | 0.312 |
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Li, P.-C.; Tsui, W.L.; Ding, D.-C. The Association between Cervical Length and Successful Labor Induction: A Retrospective Cohort Study. Int. J. Environ. Res. Public Health 2023, 20, 1138. https://doi.org/10.3390/ijerph20021138
Li P-C, Tsui WL, Ding D-C. The Association between Cervical Length and Successful Labor Induction: A Retrospective Cohort Study. International Journal of Environmental Research and Public Health. 2023; 20(2):1138. https://doi.org/10.3390/ijerph20021138
Chicago/Turabian StyleLi, Pei-Chen, Wing Lam Tsui, and Dah-Ching Ding. 2023. "The Association between Cervical Length and Successful Labor Induction: A Retrospective Cohort Study" International Journal of Environmental Research and Public Health 20, no. 2: 1138. https://doi.org/10.3390/ijerph20021138