Research
Imaging
Fetal renal artery impedance as assessed by Doppler ultrasound in pregnancies complicated by intraamniotic inflammation and preterm birth

Presented at the 28th Annual Meeting of the Society for Maternal-Fetal Medicine, Dallas, TX, Jan. 31-Feb. 2, 2008.
https://doi.org/10.1016/j.ajog.2008.11.001Get rights and content

Objective

The objective of the study was to evaluate the fetal renal artery impedance in the context of inflammation-associated preterm birth.

Study Design

We conducted a prospective Doppler assessment of the fetal renal artery impedance in 70 singleton fetuses. The study group consisted of 56 premature fetuses (median, 28.1 [interquartile range, 25.3-30.6] weeks at enrollment). Gestational age (GA) reference ranges were generated based on fetuses with uncomplicated pregnancies (n = 14). Doppler studies included renal artery pulsatility index (PI), resistance index (RI), systolic/diastolic (S/D) ratio, and presence or absence of end-diastolic blood flow. Proteomic profiling (surface-enhanced laser desorption ionization time-of-flight) was used for assessment of intraamniotic inflammation and biomarker peak corresponding to β2-microglubin. Data were interpreted in relationship to amniotic fluid index (AFI), cord blood interleukin (IL)-6 and erythropoietin (EPO) levels. The cardiovascular and metabolic profiles of the neonates were investigated in the first 24 hours of life.

Results

Fetuses delivered by mothers with intraamniotic inflammation had higher cord blood IL-6 but not EPO levels. Fetal inflammation did not affect either renal artery PI, RI, S/D ratio, or end-diastolic blood flow. Neonates delivered in the context of intraamniotic inflammation had higher serum blood urea nitrogen levels, which correlated significantly with AF IL-6 levels. The renal artery RI and SD ratio were inversely correlated with the AFI independent of GA, cord blood IL-6, and status of the membranes.

Conclusion

The fetus is capable of sustaining normal renal artery impedance despite inflammation. Resistance in the renal vascular bed affects urine output independent of inflammation.

Section snippets

Study population and research design

We evaluated fetal renal artery blood flow hemodynamics in 70 fetuses. A flow diagram of our study population is presented in Figure 1. Fifty-six fetuses (study group) were delivered by mothers who had a clinically indicated amniocentesis to rule out intraamniotic infection/inflammation. Gestational age renal artery blood flow velocity reference ranges were generated based on fetuses with uncomplicated pregnancies (n = 14) (control group). All our control fetuses were carried by asymptomatic

Results

Of the 56 women who presented with clinical signs or symptoms of preterm labor or PPROM (study group), 19 (34%) had AF proteomic profiles characteristic of intraamniotic inflammation. All 19 women had a clinically indicated preterm delivery (Figure 1). In 37 women (66%), AF infection/inflammation was excluded based on the amniocentesis results. Of these, 30 still delivered preterm. Only 5 women in the study group (14%) delivered fetuses at term. In the absence of intraamniotic

Comment

We found that a systemic fetal inflammatory response, defined as an increased cord blood IL-6 level, is not associated with detectable changes of the renal artery blood flow impedance, in utero. Thus, our original hypothesis that the fetal renal artery impedance is significantly altered in the context of intraamniotic infection/inflammation is rejected. Furthermore, we show that the process of intraamniotic inflammation is linked to elevated neonatal serum BUN levels in the first day of life.

In

Acknowledgments

We are indebted to the nurses, fellows, and residents at Department of Obstetrics, Gynecology and Reproductive Sciences, Yale New Haven Hospital, and to all patients who participated in the study. The funding source had no involvement in study design, interpretation of data, writing of the report, or decision to submit the paper for publication.

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    Cite this article as: Azpurua H, Dulay AT, Buhimschi IA, et al. Fetal renal artery impedance as assessed by Doppler ultrasound in pregnancies complicated by intraamniotic inflammation and preterm birth. Am J Obstet Gynecol 2009;200:203.e1-203.e11.

    This study was supported by National Institutes of Health (NIH)/Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) Grant R01 HD 047321 (to I.A.B.). C.S.B. was supported by the NIH/NICHD Grant R03 HD 50249, and K12 HD 1027766 (C.J.L.).

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