S. Katherine Laughon

Contemporary cesarean delivery practice in the United States

OBJECTIVE To describe contemporary cesarean delivery practice in the United States. STUDY DESIGN Consortium on Safe Labor collected detailed labor and delivery information from 228,668 electronic medical records from 19 hospitals across the United States, 2002-2008. RESULTS The overall cesarean delivery rate was 30.5%. The 31.2% of nulliparous women were delivered by cesarean section. Prelabor repeat cesarean delivery due to a previous uterine scar contributed 30.9% of all cesarean sections. The 28.8% of women with a uterine scar had a trial of labor and the success rate was 57.1%. The 43.8% women attempting vaginal delivery had induction. Half of cesarean for dystocia in induced labor were performed before 6 cm of cervical dilation. CONCLUSION To decrease cesarean delivery rate in the United States, reducing primary cesarean delivery is the key. Increasing vaginal birth after previous cesarean rate is urgently needed. Cesarean section for dystocia should be avoided before the active phase is established, particularly in nulliparous women and in induced labor.

Prepregnancy risk factors for antepartum stillbirth in the United States.

OBJECTIVE: To identify possible prepregnancy risk factors for antepartum stillbirth and to determine whether these factors identify women at higher risk for term stillbirth. METHODS: This retrospective cohort study of prepregnancy risk factors compared 712 singleton antepartum stillbirths with 174,097 singleton live births at or after 23 weeks of gestation. The risk of term antepartum stillbirth then was assessed in a subset of 155,629 singleton pregnancies. RESULTS: In adjusted multivariable analyses, African-American race, Hispanic ethnicity, maternal age 35 years or older, nulliparity, prepregnancy body mass index (BMI) 30 or higher, preexisting diabetes, chronic hypertension, smoking, and alcohol use were independently associated with stillbirth. Prior cesarean delivery and history of preterm birth were associated with increased stillbirth risk in multiparous women. The risk of a term stillbirth for women who were white, 25–29 years old, normal weight, multiparous, no chronic hypertension, and no preexisting diabetes was 0.8 per 1,000. Term stillbirth risk increased with the following conditions: preexisting diabetes (3.1 per 1,000), chronic hypertension (1.7 per 1,000), African-American race (1.8 per 1,000), maternal age 35 years or older (1.3 per 1,000), BMI 30 or higher (1 per 1,000), and nulliparity (0.9 per 1,000). CONCLUSION: There are multiple independent risk factors for antepartum stillbirth. However, the value of individual risk factors of race, parity, advanced maternal age (35–39 years old), and BMI to predict term stillbirth is poor. Our results do not support routine antenatal surveillance for any of these risk factors when present in isolation. LEVEL OF EVIDENCE: II

Thyroid Diseases and Adverse Pregnancy Outcomes in a Contemporary US Cohort

CONTEXT Thyroid diseases are inconsistently reported to increase risk for pregnancy complications. OBJECTIVE The objective of this study was to study pregnancy complications associated with common and uncommon thyroid diseases. DESIGN, SETTING, AND PARTICIPANTS We analyzed singleton pregnancies (N = 223 512) from a retrospective US cohort, the Consortium on Safe Labor (2002-2008). Thyroid diseases and outcomes were derived from electronic medical records. Multivariable logistic regression with generalized estimating equations estimated adjusted odds ratios (ORs) with 99% confidence intervals (99% CI). MAIN OUTCOME MEASURES Hypertensive diseases, diabetes, preterm birth, cesarean sections, inductions, and intensive care unit (ICU) admissions were analyzed. RESULTS Primary hypothyroidism was associated with increased odds of preeclampsia (OR = 1.47, 99% CI = 1.20-1.81), superimposed preeclampsia (OR = 2.25, 99% CI = 1.53-3.29), gestational diabetes (OR = 1.57, 99% CI = 1.33-1.86), preterm birth (OR = 1.34, 99% CI = 1.17-1.53), induction (OR = 1.15, 99% CI = 1.04-1.28), cesarean section (prelabor, OR = 1.31, 99% CI = 1.11-1.54; after spontaneous labor OR = 1.38, 99% CI = 1.14-1.66), and ICU admission (OR = 2.08, 99% CI = 1.04-4.15). Iatrogenic hypothyroidism was associated with increased odds of placental abruption (OR = 2.89, 99% CI = 1.14-7.36), breech presentation (OR = 2.09, 99% CI = 1.07-4.07), and cesarean section after spontaneous labor (OR = 2.05, 99% CI = 1.01-4.16). Hyperthyroidism was associated with increased odds of preeclampsia (OR = 1.78, 99% CI = 1.08-2.94), superimposed preeclampsia (OR = 3.64, 99% CI = 1.82-7.29), preterm birth (OR = 1.81, 99% CI = 1.32-2.49), induction (OR = 1.40, 99% CI = 1.06-1.86), and ICU admission (OR = 3.70, 99% CI = 1.16-11.80). CONCLUSIONS Thyroid diseases were associated with obstetrical, labor, and delivery complications. Although we lacked information on treatment during pregnancy, these nationwide data suggest either that there is a need for better thyroid disease management during pregnancy or that there may be an intrinsic aspect of thyroid disease that causes poor pregnancy outcomes.

Characteristics Associated With Severe Perineal and Cervical Lacerations During Vaginal Delivery

OBJECTIVE: To characterize potentially modifiable risk factors for third- or fourth-degree perineal lacerations and cervical lacerations in a contemporary U.S. obstetric practice. METHODS: The Consortium on Safe Labor collected electronic medical records from 19 hospitals within 12 institutions (228,668 deliveries from 2002 to 2008). Information on patient characteristics, prenatal complications, labor and delivery data, and maternal and neonatal outcomes were collected. Only women with successful vaginal deliveries of cephalic singletons at 34 weeks of gestation or later were included; we excluded data from sites lacking information about lacerations at delivery and deliveries complicated by shoulder dystocia; 87,267 and 71,170 women were analyzed for third- or fourth-degree and cervical lacerations, respectively. Multivariable logistic regressions were used to adjust for other factors. RESULTS: Third- or fourth-degree lacerations occurred in 2,516 women (2,223 nulliparous [5.8%], 293 [0.6%] multiparous) and cervical lacerations occurred in 536 women (324 nulliparous [1.1%], 212 multiparous [0.5%]). Risks for third- or fourth-degree lacerations included nulliparity (7.2-fold risk), being Asian or Pacific Islander, increasing birth weight, operative vaginal delivery, episiotomy, and longer second stage of labor. Increasing body mass index was associated with fewer lacerations. Risk factors for cervical lacerations included young maternal age, vacuum vaginal delivery, and oxytocin use among multiparous women, and cerclage regardless of parity. CONCLUSION: Our large cohort of women with severe obstetric lacerations reflects contemporary obstetric practices. Nulliparity and episiotomy use are important risk factors for third- or fourth-degree lacerations. Cerclage increases the risk for cervical lacerations. Many identified risk factors may not be modifiable. LEVEL OF EVIDENCE: II

Changes in labor patterns over 50 years

OBJECTIVE The objective of the study was to examine differences in labor patterns in a modern cohort compared with the 1960s in the United States. STUDY DESIGN Data from pregnancies at term, in spontaneous labor, with cephalic, singleton fetuses were compared between the Collaborative Perinatal Project (CPP, n = 39,491 delivering 1959-1966) and the Consortium on Safe Labor (CSL; n = 98,359 delivering 2002-2008). RESULTS Compared with the CPP, women in the CSL were older (26.8 ± 6.0 vs 24.1 ± 6.0 years), heavier (body mass index 29.9 ± 5.0 vs 26.3 ± 4.1 kg/m(2)), had higher epidural (55% vs 4%) and oxytocin use (31% vs 12%), and cesarean delivery (12% vs 3%). First stage of labor in the CSL was longer by a median of 2.6 hours in nulliparas and 2.0 hours in multiparas, even after adjusting for maternal and pregnancy characteristics, suggesting that the prolonged labor is mostly due to changes in practice patterns. CONCLUSION Labor is longer in the modern obstetrical cohort. The benefit of extensive interventions needs further evaluation.

Neonatal and maternal outcomes with prolonged second stage of labor.

OBJECTIVE: To assess neonatal and maternal outcomes when the second stage of labor was prolonged according to American College of Obstetricians and Gynecologists guidelines. METHODS: Electronic medical record data from a retrospective cohort (2002–2008) from 12 U.S. clinical centers (19 hospitals), including 43,810 nulliparous and 59,605 multiparous singleton deliveries at 36 weeks of gestation or greater, vertex presentation, who reached 10-cm cervical dilation were analyzed. Prolonged second stage was defined as: nulliparous women with epidural greater than 3 hours and without greater than 2 hours and multiparous women with epidural greater than 2 hours and without greater than 1 hour. Maternal and neonatal outcomes were compared and adjusted odds ratios calculated controlling for maternal race, body mass index, insurance, and region. RESULTS: Prolonged second stage occurred in 9.9% and 13.9% of nulliparous and 3.1% and 5.9% of multiparous women with and without an epidural, respectively. Vaginal delivery rates with prolonged second stage compared with within guidelines were 79.9% compared with 97.9% and 87.0% compared with 99.4% for nulliparous women with and without epidural, respectively, and 88.7% compared with 99.7% and 96.2% compared with 99.9% for multiparous women with and without epidural, respectively (P<.001 for all comparisons). Prolonged second stage was associated with increased chorioamnionitis and third-degree or fourth-degree perineal lacerations. Neonatal morbidity with prolonged second stage included sepsis in nulliparous women (with epidural: 2.6% compared with 1.2% [adjusted odds ratio (OR) 2.08, 95% confidence interval (CI) 1.60–2.70]; without epidural: 1.8% compared with 1.1% [adjusted OR 2.34, 95% CI 1.28–4.27]); asphyxia in nulliparous women with epidural (0.3% compared with 0.1% [adjusted OR 2.39, 95% CI 1.22–4.66]) and perinatal mortality without epidural (0.18% compared with 0.04% for nulliparous women [adjusted OR 5.92, 95% CI 1.43–24.51]); and 0.21% compared with 0.03% for multiparous women (adjusted OR 6.34, 95% CI 1.32–30.34). However, among the offspring of women with epidurals whose second stage was prolonged (3,533 nulliparous and 1,348 multiparous women), there were no cases of hypoxic–ischemic encephalopathy or perinatal death. CONCLUSIONS: Benefits of increased vaginal delivery should be weighed against potential small increases in maternal and neonatal risks with prolonged second stage. LEVEL OF EVIDENCE: II

Induction of Labor in a Contemporary Obstetric Cohort

OBJECTIVE We sought to describe details of labor induction, including precursors and methods, and associated vaginal delivery rates. STUDY DESIGN This was a retrospective cohort study of 208,695 electronic medical records from 19 hospitals across the United States, 2002 through 2008. RESULTS Induction occurred in 42.9% of nulliparas and 31.8% of multiparas and elective or no recorded indication for induction at term occurred in 35.5% and 44.1%, respectively. Elective induction at term in multiparas was highly successful (vaginal delivery 97%) compared to nulliparas (76.2%). For all precursors, cesarean delivery was more common in nulliparas in the latent compared to active phase of labor. Regardless of method, vaginal delivery rates were higher with a ripe vs unripe cervix, particularly for multiparas (86.6-100%). CONCLUSION Induction of labor was a common obstetric intervention. Selecting appropriate candidates and waiting longer for labor to progress into the active phase would make an impact on decreasing the national cesarean delivery rate.

Primary Cesarean Delivery in the United States

OBJECTIVES: To characterize the indications for primary cesarean delivery in a large national cohort and to identify opportunities to lower the U.S. primary cesarean delivery rate. METHODS: A retrospective cohort study of the 38,484 primary cesarean deliveries among the 228,562 deliveries at sites participating in the Consortium on Safe Labor from 2002 to 2008. RESULTS: The primary cesarean delivery rate was 30.8% for primiparous women and 11.5% for multiparous women. The most common indications for primary cesarean delivery were failure to progress (35.4%), nonreassuring fetal heart rate tracing (27.3%), and fetal malpresentation (18.5%), although frequencies for each indication varied by parity. Among women with failure to progress, 42.6% of primiparous women and 33.5% of multiparous women never progressed beyond 5 cm of dilation before delivery. Among women who reached the second stage of labor, 17.3% underwent cesarean delivery for arrest of descent before 2 hours and only 1.1% were given a trial of operative vaginal delivery. Of all primary cesarean deliveries, 45.6% were performed on primiparous women at term with a singleton fetus in cephalic presentation. CONCLUSION: Using 6 cm as the cut-off for active labor, allowing adequate time for the second stage of labor, and encouraging operative vaginal delivery, when appropriate, may be important strategies to reduce the primary cesarean delivery rate. These actions may be particularly important in the primiparous woman at term with a singleton fetus in cephalic presentation. LEVEL OF EVIDENCE: III

Precursors for Late Preterm Birth in Singleton Gestations

OBJECTIVE: To characterize precursors for late preterm birth in singletons and incidences of neonatal morbidities and perinatal mortality by gestational age and precursor. METHODS: Using retrospective observational data, we compared 15,136 gestations born late preterm with 170,593 deliveries between 37 0/7 and 41 6/7 weeks. We defined the following categories of precursors for late preterm delivery: “spontaneous labor,” “premature rupture of the membranes (preterm PROM),” “indicated” delivery, and “unknown.” Incidences of neonatal morbidities were calculated according to category of precursor stratified by gestational age at delivery. Neonatal morbidities and mortality associated with potentially avoidable deliveries (eg, “soft” precursors or elective) were compared between late preterm births and neonates born at 37–40 weeks. RESULTS: Late preterm birth comprised 7.8% of all births and 65.7% of preterm births. Percentages of precursors were 29.8% spontaneous labor, 32.3% preterm PROM, 31.8% “indicated” (obstetric, maternal, or fetal condition), and 6.1% unknown. Different precursors for delivery were associated with varying incidences of neonatal morbidity. One in 15 neonates delivered late preterm for “soft” or elective precursors, and neonatal morbidity and mortality were increased compared with delivery at or after 37 weeks for these same indications. CONCLUSION: A significant number of late preterm births were potentially avoidable. Elective deliveries should be postponed until 39 weeks of gestation. LEVEL OF EVIDENCE: II

Using a simplified Bishop score to predict vaginal delivery.

OBJECTIVE: The Bishop score is the most commonly used method to assess the readiness of the cervix for induction. However, it was created without modern statistical methods. Our objective was to determine whether a simplified score can predict vaginal delivery equally well. METHODS: Data were analyzed for 5,610 nulliparous women with singleton, uncomplicated pregnancies between 37 0/7 and 41 6/7 weeks of gestation undergoing labor induction. These women had all five components of the Bishop score recorded. Logistic regression was performed and a simplified score created with significant components. Positive and negative predictive values and positive likelihood ratios were calculated. RESULTS: In the regression model, only dilation, station, and effacement were significantly associated with vaginal delivery (P<.01). The simplified Bishop score was then devised using these three components (range 0–9) and compared with the original Bishop score (range 0–13) for prediction of successful induction, resulting in vaginal delivery. Compared with the original Bishop score (greater than 8), the simplified Bishop score (greater than 5) had a similar or better positive predictive value (87.7% compared with 87.0%), negative predictive value (31.3% compared with 29.8%), positive likelihood ratio (2.34 compared with 2.19), and correct classification rate (51.0% compared with 47.3%). Application of the simplified Bishop score in other populations, including indicated induction and spontaneous labor at term and preterm, were associated with similar vaginal delivery rates compared with the original Bishop score. CONCLUSION: The simplified Bishop score comprised of dilation, station, and effacement attains a similarly high predictive ability of successful induction as the original score. LEVEL OF EVIDENCE: II