LA PORTATA EMATICA DELLE ARTERIE UTERINE E DELLA VENA OMBELICALE NELLE GRAVIDANZE COMPLICATE DA RESTRIZIONE DI CRESCITA FETALE (IUGR)

ABSTRACT Intrauterine growth restriction (IUGR) indicates a condition in which the fetus fails to reach its growth potential genetically predetermined. This condition is associated with a higher risk of adverse perinatal outcome, especially if undetected. However, the definition of IUGR in clinical practice is challenging because some “small fetuses” might be simply constitutionally small (SGA), whether other might have suffered from growth restriction despite the fact that they present biometric parameters within normal ranges. There are some evidences to support the added value of the volume blood flow in the uterine arteries (QAUt) or in umbilical vein (QVOmb) in IUGR fetuses. Aim of the study The aim of the study is to evaluate QAUt and QVOmb in fetuses considered to be SGA or that have slowed down their growth. Particularly, we wanted to evaluate the relationship with other Doppler parameters commonly used, the possible association with adverse perinatal outcome, and the added value of blood flow volume in differentiating between SGA and IUGR. Methods This was a case-control study (1:2) in a single third referral centre. Patients were recruited during second and third trimester in the presence of abdominal circumference (AC)<10th centile or reduced fetal growth (AC crossing 50 centiles). Doppler measurements of uterine arteries (UtA), umbilical artery (AOmb), and middle cerebral artery (CMA) were performed longitudinally to assess the fetal well-being according to standard protocols. Controls were uncomplicated pregnancies with normal fetal growth and without any Doppler alteration. Evaluation of QAUt and QVOmb were performed longitudinally at each ultrasound assessment and were normalized for estimated fetal weight (EFW). Operators were blinded to volume flow measurements. Analysis in cases was performed at recruitment (diagnosis) and on last measurement before delivery. A composite adverse outcome was defined as at least one of the following: intervention due to CTG abnormalities, arterial cord blood pH<7.10 or base excess >-12 or admission to neonatal special care unit. Logistic regression models, adjusted for gestational age, were adopted to evaluate differences between the groups of dependent variables. Main findings of the study We recruited 110 cases and 220 controls. Of those 4 cases and 42 controls had to be excluded for missing outcome data or onset of some complication in control group. Thus, the analysis was performed on 106 cases and 178 controls. The QAUt and QVOmb, total and normalized for EFW, were significantly lower in fetuses with CA<10°pc or growth retardation than in controls (total QAUt, total QVOmb and normalized QVOmb all p<0.0001; QAUt normalized for EFW p=0,0005 at diagnosis and p=0,04 before delivery). Cases that had also at least one Doppler alteration had significantly lower QAUt and QVOmb, total and normalized for EFW, than controls (total QAUT p<0.0001; normalized relative QAUt p=0,0002; total and normalized QVOmb both p<0,0001). However, also fetuses without Doppler abnormalities showed significantly lower total QAUt, total and normalized for EFW QVOmb than controls (total QAUt p<0.0001; relative QAUt p=0,6; total QVOmb p<0,0001 and normalized QVOmb p=0,003). In those fetuses QVOmb, total and normalized for EFW, were significantly lower in the presence of composite adverse outcome than in controls (respectively p <0.0001; p=0.004), while there were no significant differences between those fetuses with normal outcome and controls (total QVOmb p<0.0001; normalized QVOmb p=0.06), respectively. Conclusion Blood flow volume in uterine arteries and umbilical vein might be helpful in identifying small fetuses that suffered from growth restriction in the absence of other Doppler abnormalities. Further studies are needed to prove the clinical usefulness and performance.