Objective: To explore the strength of association and the diagnostic accuracy of maternal hemodynamic parameters detected noninvasively in predicting an adverse perinatal outcome in labor.
Methods: Prospective cohort study of singleton women undergoing antepartum care at 37-39 weeks of gestation. A noninvasive ultrasonic cardiac output monitor (USCOM®) was used for cardiovascular assessment. The study outcome was a composite score of adverse perinatal outcome, which included at least one of the following variables: Cesarean or instrumental delivery for abnormal fetal heart monitoring, umbilical artery pH <7.10 or admission to neonatal special care unit. Attending clinicians were blinded to maternal cardiovascular indices. Multivariate logistic regression and area under the curve (AUC) analyses were used to test the diagnostic accuracy of different maternal and ultrasound characteristics in predicting adverse perinatal outcome.
Results: A total of 133 women were recruited. The rate of adverse perinatal outcome was 25.6% (34/133). Women who delivered without abnormal perinatal outcome (controls) were more likely to be parous, compared to those who had an adverse perinatal outcome (44.4 vs. 73.5%; p = .005). Control women had significantly lower systemic vascular resistance (SVR) (median, 1166 vs. 1352 dynes × s/cm5, p = .023) and SVR index (SVRI) (median, 2168 vs. 2627 dynes × s/cm5/m2, p = .039) compared to women who had an adverse perinatal outcome. In this latter group the prevalence of SV <50 ml was significantly higher than in the control group (38.2% (13/34) vs. 11.1%, (11/99) p = .0012). At multivariable logistic regression analysis, SVR (aOR 1.307; 95% CI 1.112-2.23), SV <50 ml (aOR 4.70; 95% CI 1.336-12.006) and parity (3.90: 95% CI 1.545-10.334) were the only variables independently associated with adverse perinatal outcome. A model considering only SVR showed an AUC of 0.631. Integration of SVR with SV <50 ml and parity significantly improves the diagnostic performance of SVR alone to predict adverse outcome (AUC 0.732; p = .016).
Conclusion: Pre-labor modifications of maternal cardiovascular variables are associated with adverse perinatal outcome. However, their predictive accuracy for perinatal compromise is low, and thus their use as standalone screening test for adverse perinatal outcome in singleton pregnancies at term is not supported.
Keywords: Maternal cardiovascular indices; USCOM; fetal distress; labor; stroke volume; systemic vascular resistances.