Alison G. Cahill

Congenital uterine anomalies and adverse pregnancy outcomes

OBJECTIVE We sought to estimate whether the presence of a maternal uterine anomaly is associated with adverse pregnancy outcomes. STUDY DESIGN This retrospective cohort study included singleton pregnancies undergoing routine anatomic survey from 1990 through 2008 at a major tertiary care medical center. Pregnancies with a diagnosis of uterine anomaly (uterine septum, unicornuate uterus, bicornuate uterus, uterine didelphys) were compared to those with normal anatomy. Primary outcomes of interest were spontaneous preterm birth (PTB), breech presentation, and cesarean delivery. RESULTS The presence of an anomaly was associated with PTB <34 weeks (adjusted odds ratio [aOR], 7.4; 95% confidence interval [CI], 4.8-11.4; P < .01), PTB <37 weeks (aOR, 5.9, 95% CI, 4.3-8.1; P < .01), primary nonbreech cesarean delivery (aOR, 2.6; 95% CI, 1.7-4.0; P < .01), preterm premature rupture of membranes (aOR, 3.2; 95% CI, 1.8-5.6; P < .01), and breech presentation (aOR, 8.6; 95% CI, 6.2-12.0; P < .01). CONCLUSION Women with a uterine anomaly are at risk for PTB, highlighting an at-risk population that needs additional study for possible interventions for PTB prevention.

Diagnosing pulmonary embolism in pregnancy using computed-tomographic angiography or ventilation-perfusion.

OBJECTIVE: To estimate the rate of nondiagnosis for patients who initially undergo computed-tomographic angiography compared with those who undergo ventilation–perfusion imaging to diagnose pulmonary embolism in pregnancy. METHODS: This was a retrospective cohort study of all women consecutively evaluated from 2001–2006 for clinical suspicion of pulmonary embolism who were pregnant or 6 weeks postpartum and underwent at least computed-tomographic angiography or ventilation–perfusion scan. Charts were abstracted for history, clinical presentation, examination, imaging, and pregnancy and maternal outcomes. Women who underwent computed-tomographic angiography for initial diagnosis were compared with women who underwent ventilation–perfusion. Primary outcome was defined as a nondiagnostic study: nondiagnostic for pulmonary embolism in the computed-tomographic angiography group, or “low or intermediate probability” in the ventilation–perfusion group. Univariable, bivariable, and multivariable analyses were performed. RESULTS: Of 304 women with a clinical suspicion of pulmonary embolism, initial diagnosis was sought by computed-tomographic angiography in 108 (35.1%) and by ventilation–perfusion in 196 (64.9%) women. Women who underwent computed-tomographic angiography tended to have a slightly higher rate of nondiagnostic study (17.0% compared with 13.2%, P=.38). Examining the subgroup of women with a normal chest X-ray, computed-tomographic angiography was much more likely to yield a nondiagnostic result than ventilation–perfusion, even after adjusting for relevant confounding effects (30.0% compared with 5.6%, adjusted odds ratio 5.4, 95% confidence interval 1.4–20.1, P<.01). CONCLUSION: Pregnant or postpartum women with clinical suspicion of a pulmonary embolism and a normal chest X-ray are more likely to have a diagnostic study from a ventilation–perfusion scan compared with a computed-tomographic angiography. Evidence supports computed-tomographic angiography as a better initial test than ventilation–perfusion in patients with an abnormal chest X-ray. LEVEL OF EVIDENCE: II

The effects of obesity on the first stage of labor.

OBJECTIVE: To estimate the effects of obesity on the duration and progression of the first stage of labor in a predominantly obese population and estimate the dose–effect with increasing classes of obesity. METHODS: We performed a retrospective cohort study of labor progression among 5,204 consecutive parturients with singleton term pregnancies (37 weeks of gestation or more) and vertex presentation who completed the first stage of labor. Two comparison groups were defined by body mass index (BMI) less than 30 (n=2,413) or 30 or more (n=2,791). Repeated-measures analysis with polynomial modeling was used to construct labor curves. The duration and progression among women with BMIs less than 30 and BMIs of 30 or more were compared in a multivariable interval-censored regression model adjusting for parity, type of labor onset, race, and birth weight more than 4,000 g. RESULTS: The labor curves indicate longer duration and slower progression of the first stage of labor among women with BMIs of 30 or more for both nulliparous and multiparous women. Multivariable interval-censored regression analysis confirmed significantly longer duration (4–10 cm: 4.7 compared with 4.1 hours, P<.01) and slower progression of cervical dilation from 4 to 6 cm (2.2 compared with 1.9 hours, P<.01 with a range of 0.5–10.0 hours) among women with BMIs of 30 or more after adjusting for confounders. CONCLUSION: The overall duration is longer and progression of the early part of the first stage of labor is slower in obese women. This suggests that obesity should be considered in defining norms for management of labor, particularly in the early part of the first stage. LEVEL OF EVIDENCE: II

Leiomyomas at routine second-trimester ultrasound examination and adverse obstetric outcomes.

OBJECTIVE: To estimate the risk of adverse pregnancy outcomes associated with the presence of leiomyomas. METHODS: This was a retrospective cohort study of all consecutive singleton pregnancies from 1990 to 2007 undergoing routine second-trimester fetal anatomic ultrasound survey. The presence or absence of leiomyomas was noted at second-trimester ultrasound examination. Primary and secondary obstetric outcomes were obtained as the individual progressed to delivery. Women with at least one leiomyoma at the time of second-trimester anatomic survey were compared with women without leiomyomas. Primary outcomes were intrauterine fetal death, breech presentation, placenta previa, cesarean delivery, placental abruption, preeclampsia, intrauterine fetal growth restriction, preterm premature rupture of membranes, and preterm birth. Univariable and multivariable analyses were performed. RESULTS: Of 72,373 women who underwent routine second-trimester anatomic survey, 64,047 women had complete obstetric follow-up data. The incidence of leiomyomas was 3.2% (n=2,058). Breech presentation (5.3% compared with 3.1%, adjusted odds ratio [OR] 1.5, 95% confidence interval [CI]1.3–1.9), placenta previa (1.4% compared with 0.5%, adjusted OR 2.2, 95% CI 1.5–3.2), cesarean delivery (33.1% compared with 24.2%, adjusted OR 1.2, 95% CI 1.1–1.4), placental abruption (1.4% compared with 0.7%, adjusted OR 2.1, 95% CI 1.4–3.0), preterm premature rupture of membranes (3.3% compared with 2.4%, adjusted OR 1.3, 95% CI 1.0–1.7), preterm birth less than 37 weeks (15.1% compared with 10.5%, adjusted OR 1.5, 95% CI 1.3–1.8), and less than 34 weeks (3.9% compared with 2.8%, adjusted OR 1.4, 95% CI 1.0–1.8), and intrauterine fetal death in women with a fetus with growth restriction (3.9% compared with 1.5%, adjusted OR 2.5, 95% CI 1.2–5.0) were significantly associated with the presence of leiomyomas. CONCLUSION: Women with leiomyomas are at low risk for obstetric complications compared with women without leiomyomas. LEVEL OF EVIDENCE: II

Higher maximum doses of oxytocin are associated with an unacceptably high risk for uterine rupture in patients attempting vaginal birth after cesarean delivery

OBJECTIVE The objective of the study was to more precisely estimate the effect of maximum oxytocin dose on uterine rupture risk in patients attempting vaginal birth after cesarean (VBAC) by considering timing and duration of therapy. STUDY DESIGN A nested case-control study was conducted within a multicenter, retrospective cohort study of more than 25,000 women with at least 1 prior cesarean delivery, comparing cases of uterine rupture with controls (no rupture) while attempting VBAC. Time-to-event analyses were performed to examine the effect of maximum oxytocin dose on the risk of uterine rupture considering therapy duration, while adjusting for confounders. RESULTS Within the nested case-control study of 804 patients, 272 were exposed to oxytocin: 62 cases of uterine rupture and 210 controls. Maximum oxytocin ranges above 20 mU/min increased the risk of uterine rupture 4-fold or greater (21-30 mU/min: hazard ratio [HR] 3.92, 95% confidence interval [CI], 1.06 to 14.52; 31-40 mU/min: HR 4.57, 95% CI, 1.00 to 20.82). CONCLUSION These findings support a maximum oxytocin dose of 20 mU/min in VBAC trials to avoid an unacceptably high risk of uterine rupture.

Association and prediction of neonatal acidemia.

OBJECTIVE The objective of this study was to estimate the predictive ability of electronic fetal monitoring (EFM) patterns immediately prior to delivery for acidemia at term birth. STUDY DESIGN This was a 4-year retrospective cohort study of 5388 consecutive singleton, nonanomalous gestations of 37 weeks or longer. The primary exposure was the EFM pattern in the 30 minutes preceding delivery. EFM patterns were prospectively interpreted using Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) nomenclature as well as non-NICHD measurements of decelerations. The primary outcome was umbilical cord arterial pH of 7.10 or less. RESULTS Four NICHD-defined EFM features within the 30 minutes prior to birth demonstrated the greatest association with acidemia: repetitive prolonged decelerations (area under the curve [AUC] 0.81), baseline tachycardia (AUC 0.80), repetitive variable decelerations (AUC 0.79), and repetitive late decelerations (0.78) after adjusting for nulliparity, fever, prolonged first stage, and obesity. A non-NICHD measure, total deceleration area, demonstrated superior predictive ability for acidemia (AUC 0.83, P = .04). CONCLUSION A non-NICHD measure of deceleration frequency and severity in the second stage performed superior to 4 NICHD EFM features for predicting fetal acidemia.

First‐trimester prediction of preeclampsia using metabolomic biomarkers: a discovery phase study

We tested the hypothesis that first‐trimester metabolic biomarkers offered a unique profile in women with preeclampsia (PE) in the second half of pregnancy, compared with controls.

Loop Electrosurgical Excision Procedure and Risk of Preterm Birth: A Systematic Review and Meta-analysis

OBJECTIVE: To assess whether loop electrosurgical excision procedure (LEEP) increases the risk for preterm birth before 37 weeks of gestation and clarify whether the increased risk for preterm birth is attributable to the procedure itself or to risk factors associated with cervical dysplasia. DATA SOURCES: Two authors performed a search of the relevant data through February 2013 using PubMed, Embase, Scopus, CENTRAL, and ClinicalTrials.gov. METHODS OF STUDY SELECTION: We included observational studies that compared rates of preterm birth in women with prior LEEP with women with no history of cervical excision. Nineteen of 559 identified studies met selection criteria. TABULATION, INTEGRATION, AND RESULTS: We compared women with a history of LEEP with two unexposed groups without a history of cervical excision: 1) women with an unknown or no history of cervical dysplasia; and 2) women with a history of cervical dysplasia but no cervical excision. The primary outcome was preterm birth before 37 weeks of gestation. Secondary outcomes were preterm birth before 34 weeks of gestation, spontaneous preterm birth, preterm premature rupture of membranes, and perinatal mortality. DerSimonian-Laird random effects models were used. We assessed heterogeneity between studies using the Q and I2 tests. Stratified analyses and metaregression were performed to assess confounding. Nineteen studies were included with a total of 6,589 patients with a history of LEEP and 1,415,015 without. Overall, LEEP was associated with an increased risk of preterm birth before 37 weeks of gestation (pooled relative risk 1.61, 95% confidence interval [CI] 1.35–1.92). However, no increased risk was found when women with a history of LEEP were compared with women with a history cervical dysplasia but no cervical excision (pooled relative risk 1.08, 95% CI 0.88–1.33). CONCLUSION: Women with a history of LEEP have similar risk of preterm birth when compared with women with prior dysplasia but no cervical excision. Common risk factors for both preterm birth and dysplasia likely explain findings of association between LEEP and preterm birth, but LEEP itself may not be an independent risk factor for preterm birth.

Association between pregnancy complications and small-for–gestational-age birth weight defined by customized fetal growth standard versus a population-based standard

Objective. To derive coefficients for developing a customized growth chart for a Mid-Western US population, and to estimate the association between pregnancy outcomes and smallness for gestational age (SGA) defined by the customized growth chart compared with a population-based growth chart for the USA. Method. A retrospective cohort study of an ultrasound database using 54,433 pregnancies meeting inclusion criteria was conducted. Coefficients for customized centiles were derived using 42,277 pregnancies and compared with those obtained from other populations. Two adverse outcome indicators were defined (greater than 7 day stay in the neonatal unit and stillbirth [SB]), and the risk for each outcome was calculated for the groups of pregnancies defined as SGA by the population standard and SGA by the customized standard using 12,456 pregnancies for the validation sample. Results. The growth potential expressed as weight at 40 weeks in this population was 3524 g (standard error: 402 g). In the validation population, 4055 cases of SGA were identified using both population and customized standards. The cases additionally identified as SGA by the customized method had a significantly increased risk of each of the adverse outcome categories. The sensitivity and specificity of those identified as SGA by customized method only for detecting pregnancies at risk for SB was 32.7% (95% confidence interval [CI] 27.0–38.8%) and 95.1% (95% CI: 94.7–95.0%) versus 0.8% (95% CI 0.1–2.7%) and 98.0% (95% CI 97.8–98.2%)for those identified by only the population-based method, respectively. Conclusion. SGA defined by customized growth potential is able to identify substantially more pregnancies at a risk for adverse outcome than the currently used national standard for fetal growth.

The association between hospital obstetrical volume and maternal postpartum complications

OBJECTIVE The purpose of this study was to examine the relationship between delivery volume and maternal complications. STUDY DESIGN We used administrative data to identify women who had been admitted for childbirth in 2006. Hospitals were stratified into deciles that were based on delivery volume. We compared composite complication rates across deciles. RESULTS We evaluated 1,683,754 childbirths in 1045 hospitals. Decile 1 and 2 hospitals had significantly higher rates of composite complications than decile 10 (11.8% and 10.1% vs 8.5%, respectively; P < .0001). Decile 9 and 10 hospitals had modestly higher composite complications as compared with decile 6 (8.8% and 8.5% vs 7.6%, respectively; P < .0001). Sixty percent of decile 1 and 2 hospitals were located within 25 miles of the nearest greater volume hospital. CONCLUSION Women who deliver at very low-volume hospitals have higher complication rates, as do women who deliver at exceedingly high-volume hospitals. Most women who deliver in extremely low-volume hospitals have a higher volume hospital located within 25 miles.