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318: The association between fetal-pelvic dimensions and labor progression
www.AJOG.org
Clinical Obstetrics, Diabetes, Labor, Medical-Surgical-Disease, Physiology/Endocrinology, Prematurity
TVDE. In the same population, no woman had a cesarean birth when the LaborPro system considered station clearly engaged (p⬍0.001). CONCLUSION: In our population, 8% of cesarean births occurred in patients with fetal head considered clinically clearly engaged, but none were when evaluated non-invasively with the LaborPro system. Such tools may therefore prevent false positive diagnosis of fetal head engagement and difficult deliveries. This tool may eventually help redefining fetal head engagement as the limit when all babies are delivered vaginally.
318 The association between fetal-pelvic dimensions and labor progression Jen Jen Chang1, Jing Wang2, David Stamilio3, Anthony Odibo3, Alison Cahill3, George Macones3 1 Saint Louis University School of Public Health, Department of Epidemiology, St. Louis, MO, 2Saint Louis University School of Public Health, Department of Biostatistics, St. Louis, MO, 3Washington University in St. Louis School of Medicine, Department of Obstetrics and Gynecology, St. Louis, MO
OBJECTIVE: To determine the association between fetal pelvic dimensions (using the fetal-pelvic index) and labor progression in nulliparous and TOLAC women. STUDY DESIGN: This prospective cohort study included nulliparous women and those undergoing trial of labor after cesarean (TOLAC), with non-anomalous pregnancies at ⱖ 37 weeks of gestation in vertex presentation (n⫽221 and 207 respectively). Fetal pelvic dimensions were assessed with the fetal pelvic index (FPI) which was calculated using ultrasound based fetal biometric measures performed within 2 weeks of delivery and x-ray pelvimetry. The primary outcome was length of active phase of the 1st stage of labor. An interval-censored regression with repeated-measures was used to construct average labor curves by FPI (positive vs. negative). A positive index value identifies a fetus that is larger than the maternal pelvis and a negative index value is smaller than the maternal pelvis. RESULTS: Women with a positive FPI had longer first stage of labor compared to those with a negative FPI score. Compared to women with a positive FPI, women with a negative FPI had significantly shorter intervals of cervical dilation after 5-6 cms. CONCLUSION: Fetal pelvic dimensions as measured by the fetal pelvic index are important determinants of the course and duration of the 1st stage of labor. Our findings may have implications in clinical management of labor and definitions used for arrest of labor.
Median duration of labor (in hours) by fetal pelvic index
Data are median (95th percentile).
319 Sweeping the fetal membranes to provoke labor: a cost-effectiveness analysis Jenna Emerson1, Jessica Fowler1, Allison Allen1, Jessica Page1, Erika Werner2, Aaron Caughey1 1 Oregon Health & Sciences University, Obstetrics and Gynecology, Portland, OR, 2Johns Hopkins University, Obstetrics and Gynecology, Baltimore, MD
OBJECTIVE: Sweeping or stripping of the fetal membranes is a commonly performed office procedure, meant to induce cervical ripening and reduce the duration of pregnancy. This study examines the outcomes and costs of this practice. STUDY DESIGN: Decision-analytic models were built using TreeAge software to compare weekly membrane sweeping beginning at 39
Poster Session II
weeks gestation to no membrane sweeping in nulliparous women. Outcomes included induction of labor, intrauterine fetal demise, neonatal death and long-term neurodevelopmental disability. All costs, benefits and probabilities were derived from the literature. Baseline assumptions included a 1.33 relative risk of going into spontaneous labor within one week following membrane sweeping. Rates of spontaneous labor and induction of labor by gestational age were derived from California Birth Registry from 1997-2006. The main outcome measure was incremental cost-effectiveness ratio (ICER) defined as marginal cost per quality-adjusted life year (QALY) gained. An ICER less than $100,000 per QALY gained was considered cost effective. Univariate sensitivity analyses were used to evaluate cost-efficacy over a wide range of values for multiple variables, including the impact of membrane stripping on spontaneous labor rates. Results were applied to a theoretical population of 100,000 women. RESULTS: In a population of 100,000 women, sweeping of the membranes results in 9,171 fewer pregnancies reaching 41 weeks gestation, 6,646 fewer inductions, and 28 fewer IUFDs. It is a cost-saving, or dominant (lower costs, better outcomes), procedure, resulting in $137 fewer dollars spent per pregnancy. Membrane sweeping remains cost effective as long as the relative risk of spontaneous labor with sweeping remains above 1.02, demonstrating that very little benefit is necessary for sweeping to be cost effective. CONCLUSION: Sweeping membranes in term nulliparous patients is a cost-effective intervention. It results in both lower costs and better outcomes than not sweeping membranes.
Sweeping of membranes
Applied to a theoretical cohort of 100,000 women.
320 Predicting the onset of spontaneous labour (OSL) in post date pregnancies Jennifer Hutcheon1, Lily Lee2, Gerald Marquette1 1 University of British Columbia, Obstetrics and Gynaecology, Vancouver, BC, Canada, 2Provincial Health Services Authority, Perinatal Services British Columbia, Vancouver, BC, Canada
OBJECTIVE: To calculate the daily probability of the OSL between 41⫹0 and 42⫹0 weeks of gestation and to identify determinants of this occurrence. STUDY DESIGN: Data from women with uncomplicated pregnancies carrying a single fetus in cephalic presentation and ultrasound-confirmed dating at or beyond 41⫹0 weeks were extracted from the British Columbia Perinatal Data Registry (2008-2011). Pregnancies were followed until the time (hh:mm) of OSL, onset of labour following induction or delivery by pre-labour Cesarean. A Kaplan Meier curve was created to estimate the probability of OSL. Multivariable Cox regression was used to assess if maternal age, parity, pre-pregnancy BMI and gestational weight gain were independent predictors of OSL. The model’s value in individualized prediction of OSL was assessed using the c-statistic. RESULTS: 9331 eligible women were included. Table 1 shows the estimated probability of OSL. The probability of OSL increased significantly with increased parity (Hazard Ratio (HR) ⫽ 1.31 [95% Confidence Interval (CI) 1.22,1.41] for parous women vs nulliparous women), and decreased significantly with increasing maternal age (HR⫽0.95 [95% CI 0.92, 0.99 per 5-year increase]), pre-pregnancy BMI (HR⫽0.88 [95% CI 0.85, 0.91 per 5-kg/m2 increase]) and gestational weight gain (HR⫽0.94 [95% CI 0.91, 0.96 per 5-kg increase]). The model’s c-statistic was 0.56. CONCLUSION: The probability of OSL in post-date pregnancies differs significantly according to parity, maternal age, BMI and gestational
Supplement to JANUARY 2013 American Journal of Obstetrics & Gynecology
S143
Clinical Obstetrics, Diabetes, Labor, Medical-Surgical-Disease, Physiology/Endocrinology, Prematurity
TVDE. In the same population, no woman had a cesarean birth when the LaborPro system considered station clearly engaged (p⬍0.001). CONCLUSION: In our population, 8% of cesarean births occurred in patients with fetal head considered clinically clearly engaged, but none were when evaluated non-invasively with the LaborPro system. Such tools may therefore prevent false positive diagnosis of fetal head engagement and difficult deliveries. This tool may eventually help redefining fetal head engagement as the limit when all babies are delivered vaginally.
318 The association between fetal-pelvic dimensions and labor progression Jen Jen Chang1, Jing Wang2, David Stamilio3, Anthony Odibo3, Alison Cahill3, George Macones3 1 Saint Louis University School of Public Health, Department of Epidemiology, St. Louis, MO, 2Saint Louis University School of Public Health, Department of Biostatistics, St. Louis, MO, 3Washington University in St. Louis School of Medicine, Department of Obstetrics and Gynecology, St. Louis, MO
OBJECTIVE: To determine the association between fetal pelvic dimensions (using the fetal-pelvic index) and labor progression in nulliparous and TOLAC women. STUDY DESIGN: This prospective cohort study included nulliparous women and those undergoing trial of labor after cesarean (TOLAC), with non-anomalous pregnancies at ⱖ 37 weeks of gestation in vertex presentation (n⫽221 and 207 respectively). Fetal pelvic dimensions were assessed with the fetal pelvic index (FPI) which was calculated using ultrasound based fetal biometric measures performed within 2 weeks of delivery and x-ray pelvimetry. The primary outcome was length of active phase of the 1st stage of labor. An interval-censored regression with repeated-measures was used to construct average labor curves by FPI (positive vs. negative). A positive index value identifies a fetus that is larger than the maternal pelvis and a negative index value is smaller than the maternal pelvis. RESULTS: Women with a positive FPI had longer first stage of labor compared to those with a negative FPI score. Compared to women with a positive FPI, women with a negative FPI had significantly shorter intervals of cervical dilation after 5-6 cms. CONCLUSION: Fetal pelvic dimensions as measured by the fetal pelvic index are important determinants of the course and duration of the 1st stage of labor. Our findings may have implications in clinical management of labor and definitions used for arrest of labor.
Median duration of labor (in hours) by fetal pelvic index
Data are median (95th percentile).
319 Sweeping the fetal membranes to provoke labor: a cost-effectiveness analysis Jenna Emerson1, Jessica Fowler1, Allison Allen1, Jessica Page1, Erika Werner2, Aaron Caughey1 1 Oregon Health & Sciences University, Obstetrics and Gynecology, Portland, OR, 2Johns Hopkins University, Obstetrics and Gynecology, Baltimore, MD
OBJECTIVE: Sweeping or stripping of the fetal membranes is a commonly performed office procedure, meant to induce cervical ripening and reduce the duration of pregnancy. This study examines the outcomes and costs of this practice. STUDY DESIGN: Decision-analytic models were built using TreeAge software to compare weekly membrane sweeping beginning at 39
Poster Session II
weeks gestation to no membrane sweeping in nulliparous women. Outcomes included induction of labor, intrauterine fetal demise, neonatal death and long-term neurodevelopmental disability. All costs, benefits and probabilities were derived from the literature. Baseline assumptions included a 1.33 relative risk of going into spontaneous labor within one week following membrane sweeping. Rates of spontaneous labor and induction of labor by gestational age were derived from California Birth Registry from 1997-2006. The main outcome measure was incremental cost-effectiveness ratio (ICER) defined as marginal cost per quality-adjusted life year (QALY) gained. An ICER less than $100,000 per QALY gained was considered cost effective. Univariate sensitivity analyses were used to evaluate cost-efficacy over a wide range of values for multiple variables, including the impact of membrane stripping on spontaneous labor rates. Results were applied to a theoretical population of 100,000 women. RESULTS: In a population of 100,000 women, sweeping of the membranes results in 9,171 fewer pregnancies reaching 41 weeks gestation, 6,646 fewer inductions, and 28 fewer IUFDs. It is a cost-saving, or dominant (lower costs, better outcomes), procedure, resulting in $137 fewer dollars spent per pregnancy. Membrane sweeping remains cost effective as long as the relative risk of spontaneous labor with sweeping remains above 1.02, demonstrating that very little benefit is necessary for sweeping to be cost effective. CONCLUSION: Sweeping membranes in term nulliparous patients is a cost-effective intervention. It results in both lower costs and better outcomes than not sweeping membranes.
Sweeping of membranes
Applied to a theoretical cohort of 100,000 women.
320 Predicting the onset of spontaneous labour (OSL) in post date pregnancies Jennifer Hutcheon1, Lily Lee2, Gerald Marquette1 1 University of British Columbia, Obstetrics and Gynaecology, Vancouver, BC, Canada, 2Provincial Health Services Authority, Perinatal Services British Columbia, Vancouver, BC, Canada
OBJECTIVE: To calculate the daily probability of the OSL between 41⫹0 and 42⫹0 weeks of gestation and to identify determinants of this occurrence. STUDY DESIGN: Data from women with uncomplicated pregnancies carrying a single fetus in cephalic presentation and ultrasound-confirmed dating at or beyond 41⫹0 weeks were extracted from the British Columbia Perinatal Data Registry (2008-2011). Pregnancies were followed until the time (hh:mm) of OSL, onset of labour following induction or delivery by pre-labour Cesarean. A Kaplan Meier curve was created to estimate the probability of OSL. Multivariable Cox regression was used to assess if maternal age, parity, pre-pregnancy BMI and gestational weight gain were independent predictors of OSL. The model’s value in individualized prediction of OSL was assessed using the c-statistic. RESULTS: 9331 eligible women were included. Table 1 shows the estimated probability of OSL. The probability of OSL increased significantly with increased parity (Hazard Ratio (HR) ⫽ 1.31 [95% Confidence Interval (CI) 1.22,1.41] for parous women vs nulliparous women), and decreased significantly with increasing maternal age (HR⫽0.95 [95% CI 0.92, 0.99 per 5-year increase]), pre-pregnancy BMI (HR⫽0.88 [95% CI 0.85, 0.91 per 5-kg/m2 increase]) and gestational weight gain (HR⫽0.94 [95% CI 0.91, 0.96 per 5-kg increase]). The model’s c-statistic was 0.56. CONCLUSION: The probability of OSL in post-date pregnancies differs significantly according to parity, maternal age, BMI and gestational
Supplement to JANUARY 2013 American Journal of Obstetrics & Gynecology
S143