Retrospective validation of ultrasound characteristics at 19-24 weeks as predictive tools for selective intrauterine growth restriction in monochorionic diamniotic twin pregnancies: a diagnostic study.

Background: Seeking an optimal time point for ultrasound examination is important for the diagnosis of late selective intrauterine growth restriction (sIUGR) at birth in monochorionic diamniotic (MCDA) twin pregnancies. We aimed to assess the role of ultrasound characteristics at 19-24 weeks as predictive tools for late sIUGR at birth in MCDA twin pregnancies.

Methods: We retrospectively recruited 32 sIUGR and 56 normal patients with MCDA twin pregnancies. Ultrasound indexes of these included subjects at 19-24 weeks, including the middle cerebral artery peak systolic velocity (MCA-PSV), umbilical artery pulsatility index (UA-PI), middle cerebral artery pulsatility index (MCA-PI), and cerebroplacental ratio (CPR) were assessed. Receiver operating characteristic (ROC) curves were used to ascertain the predictive value of ultrasound characteristics discrepancy for such complications, and the relationship between the ultrasound characteristics and sIUGR was assessed by a logistic regression analysis.

Results: Differences were found in the MCA-PI, UA-PI, and CPR discordances between the normal MCDA and sIUGR subjects. CPR discordance was the most effective characteristic for predicting sIUGR [area under the ROC curve (AUC) =0.883; 95% CI: 0.795-0.948], followed by UA-PI discordance (AUC =0.772; 95% CI: 0.685-0.829), and MCA-PI discordance (AUC =0.746; 95% CI: 0.681-0.823), respectively. Additionally, the optimal cutoff value of CPR discordance was 21.65, and the corresponding sensitivity and specificity were 0.750 and 0.929, respectively. The correlation analysis revealed that gestational age (GA) at ultrasound scan but not at delivery was significantly correlated with the MCA-PSV (r=0.55, P<0.01), UA-PI (r=0.55, P<0.01), MCA-PI (r=0.49, P<0.01), and CPR (r=0.55, P<0.01) in sIUGR, while GA at both ultrasound scan and birth was significantly correlated with MCA-PSV (r=0.65, P<0.01), UA-PI (r=0.49, P<0.01), MCA-PI (r=0.48, P<0.01), and CPR (r=0.63, P<0.01) in normal MCDA.

Conclusions: Increased MCA-PI, UA-PI, and CPR discordances were found in fetuses with sIUGR. CPR discordance could serve as a predictive index for sIUGR. An early ultrasound examination may be more accurate than biochemical modality for sIUGR prediction.