ABSTRACT
BACKGROUND: Research on the definition of fetal growth restriction has focused on predicting adverse perinatal outcomes. A significant limitation of this approach is that the individual outcomes of interest could be related to the condition and the treatment. Evaluation of outcomes that reflect the pathophysiology of fetal growth restriction may overcome this limitation. OBJECTIVE: To compare the diagnostic performance of the fetal growth restriction definitions established by the International Society for Ultrasound in Obstetrics and Gynecology and the Society for Maternal-Fetal Medicine to predict placental histopathological findings associated with placental insufficiency and a composite adverse neonatal outcome. STUDY DESIGN: In this retrospective cohort study of singleton pregnancies, the International Society for Ultrasound in Obstetrics and Gynecology and the Society for Maternal-Fetal Medicine guidelines were used to identify pregnancies with fetal growth restriction and a corresponding control group. The primary outcome was the prediction of placental histopathological findings associated with placental insufficiency, defined as lesions associated with maternal vascular malperfusion. A composite adverse neonatal outcome (i.e., umbilical artery pH≤7.1, Apgar score at 5 minutes ≤4, neonatal intensive care unit admission, hypoglycemia, respiratory distress syndrome requiring mechanical ventilation, intrapartum fetal distress requiring expedited delivery, and perinatal death) was investigated as a secondary outcome. Sensitivity, specificity, positive and negative predictive values, and the areas under the receiver-operating-characteristics curves were determined for each fetal growth restriction definition. Logistic regression models were used to assess the association between each definition and the studied outcomes. A subgroup analysis of the diagnostic performance of both definitions stratifying the population in early and late fetal growth restriction was also performed. RESULTS: Both societies' definitions showed a similar diagnostic performance as well as a significant association with the primary (International Society for Ultrasound in Obstetrics and Gynecology adjusted odds ratio 3.01 [95% confidence interval 2.42, 3.75]; Society for Maternal-Fetal Medicine adjusted odds ratio 2.85 [95% confidence interval 2.31, 3.51]) and secondary outcomes (International Society for Ultrasound in Obstetrics and Gynecology adjusted odds ratio 1.95 [95% confidence interval 1.56, 2.43]; Society for Maternal-Fetal Medicine adjusted odds ratio 2.12 [95% confidence interval 1.70, 2.65]). Furthermore, both fetal growth restriction definitions had a limited discriminatory capacity for placental histopathological findings of maternal vascular malperfusion and the composite adverse neonatal outcome (area under the receiver-operating-characteristics curve International Society for Ultrasound in Obstetrics and Gynecology 0.63 [95% confidence interval 0.61, 0.65], 0.59 [95% confidence interval 0.56, 0.61]; area under the receiver-operating-characteristics Society for Maternal-Fetal Medicine 0.63 [95% confidence interval 0.61, 0.66], 0.60 [95% confidence interval 0.57, 0.62]). CONCLUSIONS: The International Society for Ultrasound in Obstetrics and Gynecology and the Society for Maternal-Fetal Medicine fetal growth restriction definitions have limited discriminatory capacity for placental histopathological findings associated with placental insufficiency and a composite adverse neonatal outcome.
