The prediction of morbidity related to vaginal delivery in nulliparous women - A secondary analysis from the genesis multicenter trial.

OBJECTIVE: In the prospective multicenter Genesis study, we developed a prediction model for Cesarean delivery (CD) in term nulliparous women. The objective of this secondary analysis was to determine whether the Genesis model has the potential to predict maternal and neonatal morbidity associated with vaginal delivery. STUDY DESIGN: The national prospective Genesis trial recruited 2,336 nulliparous women with a vertex presentation between 39 + 0- and 40 + 6-weeks' gestation from seven tertiary centers. The prediction model used five parameters to assess the risk of CD: maternal age, maternal height, body mass index, fetal head circumference and fetal abdominal circumference. Simple and multiple logistic regression analyses were used to develop the Genesis model. The risk score calculated using this model were correlated with maternal and neonatal morbidity in women who delivered vaginally: postpartum hemorrhage (PPH), obstetric anal sphincter injury (OASI), shoulder dystocia, one- and five-minute Apgar score ≤ 7, neonatal intensive care (NICU) admission, cephalohematoma, fetal laceration, nerve palsy and fractures. The morbidities associated with spontaneous vaginal delivery were compared with those associated with operative vaginal delivery (OVD). The likelihood ratios for composite morbidity and the morbidity associated with OVD based on the Genesis risk scores were also calculated. RESULTS: A total of 1,845 (79%) nulliparous women had a vaginal delivery. A trend of increasing intervention and morbidity was observed with increasing Genesis risk score, including OVD (p < 0.001), PPH (p < 0.008), NICU admission (p < 0.001), low Apgar score at one-minute (p < 0.001) and OASI (p = 0.009). The morbidity associated with OVD was significantly higher compared to spontaneous vaginal delivery, including NICU admission (p < 0.001), PPH (p = 0.022), birth injury (p < 0.001), shoulder dystocia (p = 0.002) and Apgar score of<7 at one-minute (p < 0.001). The positive likelihood ratios for composite outcomes (where the OVD was excluded) increases with increasing risk score from 1.005 at risk score of 5% to 2.507 for risk score of>50%. CONCLUSION: In women who ultimately achieved a vaginal birth, we have shown more maternal and neonatal morbidity in the setting of a Genesis nomogram-determined high-risk score for intrapartum CD. Therefore, the Genesis prediction tool also has the potential to predict a more morbid vaginal delivery.

Inter-hospital comparison of Cesarean delivery rates should not be considered to reflect quality of care without consideration of patient heterogeneity: An observational study.

OBJECTIVE: Contemporary approaches to monitoring quality of care in obstetrics often focus on comparing Cesarean Delivery rates. Varied rates can complicate interpretation of quality of care. We previously developed a risk prediction tool for nulliparous women who may require intrapartum Cesarean delivery which identified five key predictors. Our objective with this study was to ascertain if patient heterogeneity can account for much of the observed variation in Cesarean delivery rates, thereby enabling Cesarean delivery rates to be a better marker of quality of care. MATERIALS AND METHODS: This is a secondary analysis of the Genesis study. This was a large prospective study of 2336 nulliparous singleton pregnancies recruited at seven hospitals. A heterogeneity score was calculated for each hospital. An adjusted Cesarean delivery rate was also calculated incorporating the heterogeneous risk score. RESULTS: A cut-off at the 90th percentile was determined for each predictive factor. Above the 90th percentile was considered to represent 'high risk' (with the exception of maternal height which identified those below the 10th percentile). The patient heterogeneous risk score was defined as the number of risk factors > 90th percentile (<10th percentile for height). An unequal distribution of high-risk patients between centers was observed (p < 0.001). The correlation between the Cesarean delivery rate and the patient heterogeneous risk score was high (0.76, p < 0.05). When adjusted for patient heterogeneity, Cesarean delivery rates became closer aligned. CONCLUSION: Inter-institutional diversity is common. We suggest that crude comparison of Cesarean delivery rates between different hospitals as a marker of care quality is inappropriate. Allowing for marked differences in patient characteristics is essential for correct interpretation of such comparisons.

Defining the upper limit of the second stage of labor in nulliparous patients.

BACKGROUND: Increased duration of the second stage of labor provides clinical challenges in decision-making regarding the optimal mode of delivery that minimizes maternal and neonatal morbidity. OBJECTIVE: In a large cohort of uncomplicated nulliparous singleton cephalic labors, we sought to examine the effect of increasing duration of second stage on delivery and perinatal outcome. STUDY DESIGN: The GENESIS Study recruited 2336 nulliparous patients with vertex presentation in a prospective double-blinded study to examine prenatal and intrapartum predictors of delivery. Metrics included maternal demographics, duration of second stage, mode of delivery, and associated maternal and neonatal outcomes. Indicators of morbidity included third- or fourth-degree tear, postpartum hemorrhage, neonatal intensive care unit admission, low Apgar scores, cord pH <7.20 and a composite of birth injury that included cephalohematoma, fetal laceration, brachial plexus palsy, facial nerve palsy, and fetal fracture. RESULTS: Of 2336 recruited nulliparous participants, 1872 reached the second stage of labor and had complete data for analysis. Increased maternal age (P=.02) and birthweight (P<.001) were found to be associated with a longer second stage. Increasing second stage duration was found to impact on mode of delivery, such that at <1 hour duration the spontaneous vaginal delivery rate was 63% vs 24% at >3 hours (P<.001). Operative vaginal delivery increased from 35% at <1 hour to 65% at >3 hours (P<.001). The rate of cesarean delivery increased with duration of the second stage from 1.2% at <1 hour to 11% at >3 hours (P<.001). The rates of third- or fourth-degree tear increased with second stage duration (P=.003), as did postpartum hemorrhage (P<.001). The composite neonatal birth injury rate increased from 1.8% at <1 hour to 3.4% at >3 hours. The maximum rate of birth injury was 6.5% at 2-3 hours (P<.001). Multiple logistic regression analysis that controlled for maternal age and birthweight confirmed that operative vaginal delivery, perineal trauma, postpartum hemorrhage, and neonatal birth injury remained significantly more likely with increasing second stage duration. CONCLUSION: In a prospective cohort of nulliparous pregnancies, increasing duration of second stage of labor was associated with increased rates of operative vaginal and cesarean delivery. Although almost 90% of term nulliparous women with a second stage of labor >3 hours will succeed in achieving a vaginal birth, this success comes at a maternal morbidity cost, with a 10% risk of severe perineal injury and an increasing rate of significant neonatal injury.

The Impact of Aspirin on Ultrasound Markers of Uteroplacental Flow in Low-Risk Pregnancy: Secondary Analysis of a Multicenter RCT.

OBJECTIVE: This article evaluates the effect of low-dose aspirin on uterine artery (UtA) Doppler, placental volume, and vascularization flow indices in low-risk pregnancy. STUDY DESIGN: In this secondary analysis of the TEST randomized controlled trial, low-risk nulliparous women were originally randomized at 11 weeks to: (1) routine aspirin 75 mg; (2) no aspirin; and (3) aspirin based upon the preeclampsia Fetal Medicine Foundation screening test. UtA Doppler, three-dimensional (3D) placental volume, and vascularization flow indices were assessed prior to and 6 weeks postaspirin commencement. RESULTS: A total of 546 women were included (aspirin n = 192, no aspirin n = 354). Between first and second trimesters, aspirin use was not associated with a change in UtA Doppler, placental volume, or vascular flow indices. There was no significant difference in the change in UtA Doppler pulsatility index (PI) Z-scores or notching (PI Z-score -0.2 vs. -0.2, p = 0.17), nor was there a significant change in placental volume Z-score and vascular flow indices (volume Z-score change: 0.74 vs. 0.62, p = 0.34). CONCLUSION: Low-dose aspirin commenced at 11 weeks in low-risk women does not appear to improve uterine and placental perfusion or placental volume. Any perceived effect on uteroplacental vasculature is not reflected in changes in placental volume nor uteroplacental flow as assessed by two-dimensional and 3D ultrasound.

Prediction of cesarean delivery in the term nulliparous woman: results from the prospective, multicenter Genesis study.

BACKGROUND: In contemporary practice many nulliparous women require intervention during childbirth such as operative vaginal delivery or cesarean delivery (CD). Despite the knowledge that the increasing rate of CD is associated with increasing maternal age, obesity and larger infant birthweight, we lack a reliable method to predict the requirement for such potentially hazardous obstetric procedures during labor and delivery. This issue is important, as there are greater rates of morbidity and mortality associated with unplanned CD performed in labor compared with scheduled CDs. A prediction algorithm to identify women at risk of an unplanned CD could help reduced labor associated morbidity. OBJECTIVE: In this primary analysis of the Genesis study, our objective was to prospectively assess the use of prenatally determined, maternal and fetal, anthropomorphic, clinical, and ultrasound features to develop a predictive tool for unplanned CD in the term nulliparous woman, before the onset of labor. MATERIALS AND METHODS: The Genesis study recruited 2336 nulliparous women with a vertex presentation between 39+0 and 40+6 weeks' gestation in a prospective multicenter national study to examine predictors of CD. At recruitment, a detailed clinical evaluation and ultrasound assessment were performed. To reduce bias from knowledge of these data potentially influencing mode of delivery, women, midwives, and obstetricians were blinded to the ultrasound data. All hypothetical prenatal risk factors for unplanned CD were assessed as a composite. Multiple logistic regression analysis and mathematical modeling was used to develop a risk evaluation tool for CD in nulliparous women. Continuous predictors were standardized using z scores. RESULTS: From a total enrolled cohort of 2336 nulliparous participants, 491 (21%) had an unplanned CD. Five parameters were determined to be the best combined predictors of CD. These were advancing maternal age (odds ratio [OR], 1.21; 95% confidence interval [CI], 1.09 to 1.34), shorter maternal height (OR, 1.72; 95% CI, 1.52 to 1.93), increasing body mass index (OR, 1.29; 95% CI, 1.17 to 1.43), larger fetal abdominal circumference (OR, 1.23; 95% CI, 1.1 to 1.38), and larger fetal head circumference (OR, 1.27; 95% CI, 1.14 to 1.42). A nomogram was developed to provide an individualized risk assessment to predict CD in clinical practice, with excellent calibration and discriminative ability (Kolmogorov-Smirnov, D statistic, 0.29; 95% CI, 0.28 to 0.30) with a misclassification rate of 0.21 (95% CI, 0.19 to 0.25). CONCLUSION: Five parameters (maternal age, body mass index, height, fetal abdominal circumference, and fetal head circumference) can, in combination, be used to better determine the overall risk of CD in nulliparous women at term. A risk score can be used to inform women of their individualized probability of CD. This risk tool may be useful for reassuring most women regarding their likely success at achieving an uncomplicated vaginal delivery as well as selecting those patients with such a high risk for CD that they should avoid a trial of labor. Such a risk tool has the potential to greatly improve planning hospital service needs and minimizing patient risk.

Pregnancy outcome of monochorionic twins: does amnionicity matter?

OBJECTIVE: To compare the fetal loss rate of monochorionic (MC) twin pregnancies according to their amnionicity. METHODS: A retrospective review of all MC pregnancy outcomes in a tertiary centre. Pregnancy outcomes were compared for monochorionic monoamniotic (MCMA) versus monochorionic diamniotic (MCDA) pregnancies. RESULTS: 29 MCMA and 117 MCDA twin pregnancies were identified. The overall fetal loss rate was significantly higher in MCMA (23/52, 44.2%) compared to MCDA pregnancies (28/233, 12%, Chi squared = 30.03, p < .001). Kaplan-Meier analysis showed that fetal survival rate in MCDA twins were significantly higher than in MCMA twins (Log-rank Chi-squared = 27.9, p < .0005). Early pregnancy ultrasound identified the causes for these fetal losses in some MCMA twins. After exclusion of identifiable causes, the difference in fetal survival was not significant in the two groups (Log-rank chi-squared = 0.373, p = .54). CONCLUSION: The loss rate for MCMA twins is high and occurs mainly due to discordant congenital abnormality, conjoint twins or twin reversed arterial perfusion (TRAP) sequence. Although the fetal loss rate in MCDA is lower than in MCMA pregnancies, the majority of fetal loss in MCDA pregnancies cannot be predicted at the first scan at presentation. The data of this study questions the widespread policy of a difference in the scheduling of elective delivery for MCMA and MCDA twins.

Detection of foetal growth restriction using third trimester ultrasound.

Foetal growth restriction is an important contributor to perinatal mortality, being responsible for up to 50% of stillbirths. Optimal prevention and accurate detection enabling timely intervention remain elusive, particularly in presumed low-risk pregnancy. Third trimester ultrasound seems a logical solution, but systematic review of evidence from randomised trials has shown that third trimester ultrasound does not have a significant impact on perinatal mortality but may increase interventions such as caesarean delivery. However, the evidence is difficult to interpret in the context of current obstetric practice as the evolution of ultrasound technology and rapid assimilation of newer techniques has resulted in questionable validity of the findings. If third trimester ultrasound were introduced routinely, there is a need to decide the optimal timing and number of examinations and what ultrasound parameters should be used to identify the foetus at risk.