Sovio U, et al. - Researchers performed a comparison of the association between risk of emergency Cesarean delivery (CD) and non-customized vs customized ultrasound estimated fetal weight (EFW) at 36weeks' gestation and assessed if an addition of ultrasound EFW to a model based on maternal characteristics alone improved prediction of emergency CD. Further, they examined the screening performance of a multivariable model using both EFW and maternal characteristics in predicting emergency CD and ascertained if women at high predicted risk of emergency CD based on this model had higher risk of maternal and perinatal morbidity compared with screen-negative women. As per outcomes, women at increased risk of subsequent emergency CD could be identified with ultrasound EFW at 36-weeks, combined with maternal characteristics. Increased risk of maternal and perinatal morbidity was observed for these women in comparison to those at low risk of emergency CD and those having CD for breech presentation at term.

Methods

• From the prospective Pregnancy Outcome Prediction study (Cambridge, UK) cohort, 3047 low-risk (no pre-existing medical conditions or acquired complications of pregnancy) nulliparous women, who underwent ultrasound EFW at ~36 weeks' gestation were studied.
• To fetal biometry results, both the women and their clinicians were blinded.
• Delivery by Cesarean section in pregnancies in which the date of delivery had not been prearranged was defined as emergency CD.
• Maternal age, height, body mass index (BMI), weight gain, fetal abdominal circumference growth velocity and fetal sex were evaluated as the additional candidate predictors of emergency CD.
• Using routinely collected data from 55,337 births in Scotland between 2003 and 2008, researchers performed external validation of the predictive model.
• They defined women with an estimated risk of emergency CD ≥ 40% as screen positive.

Results

• Findings suggested a strong association of blinded EFW with the risk of emergency CD (coefficient for increase of 1 SD in EFW, 0.39 (95% CI, 0.30–0.48); odds ratio (OR), 1.48 (95% CI, 1.35–1.62)).
• Similar coefficient for customized EFW was observed(0.42 (95% CI, 0.33–0.51); OR, 1.53 (95% CI, 1.39–1.67)); hence, non-customized EFW was employed subsequently for simplicity.
• A multivariable logistic regression model combining maternal characteristics (age, height, BMI and weight gain between 12 and 36 weeks) was shown to have moderate predictive value for emergency CD (area under the receiver–operating characteristics curve (AUC) = 0.68).
• Increased AUC to 0.71 and improved prediction were noted with the addition of blinded EFW to the model (likelihood-ratio test P < 0.0001).
• They identified 189 (6.2%) women who screened positive based on this model; 48% of these delivered by CD.
• Screen-positive women vs screen-negative women demonstrated elevated risks of severe postpartum hemorrhage (relative risk (RR), 2.49; 95% CI, 1.83–3.38), any adverse neonatal outcome (RR, 1.86; 95% CI, 1.22–2.82) and severe adverse neonatal outcome (RR, 4.03; 95% CI, 1.35–12.03).
• Screen-positive women also displayed higher risks of these events compared with women who had a term CD for breech presentation.
• In this study, the model showed similar predictive value for the risk of emergency CD and perinatal morbidity when evaluated using the dataset from Scotland.