Development of Gestational Age-Specific Nomograms for Fetal Splenic Artery Doppler Parameters Between 18 and 40 Weeks of Gestation

Abstract

OBJECTIVE: To characterize the gestational age-related behavior of fetal splenic artery (SA) Doppler parameters and to establish appropriate reference models for the systolic/diastolic (S/D) ratio, pulsatility index (PI), peak systolic velocity (PSV), and time-averaged maximum velocity (TAMV) in normal singleton pregnancies between 18 and 40 weeks of gestation.

STUDY DESIGN: This prospective observational cross-sectional study included 103 normal singleton pregnancies undergoing routine obstetric ultrasonographic examination between 18 and 40 weeks of gestation. SA Doppler waveforms were obtained using a standardized technique, and the S/D ratio, PI, PSV, and TAMV were recorded. We modeled the relationship between gestational age and each parameter using linear and quadratic regression analysis and derived gestational age-specific Z-score equations and percentile reference values (5th, 10th, 50th, 90th, and 95th). Gestational age-specific modeling was applied to PSV and TAMV; PI, which showed no gestational age dependence, was reported as a single pooled reference interval, and S/D, which could not be adequately modeled parametrically, was reported descriptively. Correlations between SA Doppler parameters and gestational age, fetal biometric parameters, and umbilical artery (UA) Doppler indices were assessed using Spearman correlation analysis.

RESULTS: SA PSV and TAMV increased significantly with advancing gestational age (PSV=−5.651+1.587×GA, R²=0.399, p<0.001; TAMV=−10.900+0.929×GA, R²=0.401, p<0.001), whereas the SA S/D ratio and PI showed no significant association with gestational age. SA PSV and TAMV correlated positively with abdominal circumference and estimated fetal weight (r=0.632-0.674, all p<0.001) and negatively with UA Doppler indices. In contrast, SA S/D correlated positively with the UA S/D ratio (r=0.405, p=0.006).

CONCLUSION: This study provides gestational age-specific nomograms and Z-score equations for SA PSV and TAMV, a pooled reference interval for SA PI, and descriptive values for SA S/D in normal pregnancy. These reference values may serve as a normative foundation for future research examining SA hemodynamics in relation to fetal growth, anemia, and pancreatic development.