Spiral artery blood flow during pregnancy: a systematic review and meta-analysis.

Abstract

Background: Downstream remodeling of the spiral arteries (SpA) decreases utero-placental resistance drastically, allowing sustained and increased blood flow to the placenta at all circumstances. We systematically evaluated available reports to visualize adaptation of spiral arteries throughout pregnancy by ultra-sonographic measurements and evaluated when this process is completed. Methods: A systematic review and meta-analysis of spiral artery flow (pulsatility index (PI), resistance index (RI) and peak systolic velocity (PSV)) was performed. English articles were obtained from Pubmed, EMBASE and Cochrane Library and included articles were assessed on quality and risk of bias. Weighted means of Doppler indices were calculated using a random-effects model. Results: In healthy pregnancies, PI and RI decreased from 0.80 (95% CI: 0.70-0.89) and 0.50 (95% CI: 0.47-0.54) in the first trimester to 0.50 (95% CI: 0.45-0.55, p<0.001) and 0.39 (95% CI: 0.37-0.42, p<0.001) in the second trimester and to 0.49 (95% CI: 0.44-0.53, p=0.752) and 0.36 (95% CI: 0.35-0.38, p=0.037) in the third trimester, respectively. In parallel, PSV altered from 0.22 m/s (95% CI: 0.13-0.30 m/s) to 0.28 m/s (95% CI: 0.17-0.40 m/s, p=0.377) and to 0.25 m/s (95% CI: 0.20-0.30 m/s, p=0.560) in the three trimesters. In absence of second and third trimester Doppler data in complicated gestation, only a difference in PI was observed between complicated and healthy pregnancies during the first trimester (1.49 vs 0.80, p<0.001). Although individual studies have identified differences in PI between SpA located in the central part of the placental bed versus those located at its periphery, this meta-analysis could not confirm this (p=0.349). Conclusions: This review and meta-analysis concludes that an observed decrease of SpA PI and RI from the first towards the second trimester parallels the physiological trophoblast invasion converting SpA during early gestation, a process completed in the midst of the second trimester. Higher PI was found in SpA of complicated pregnancies compared to healthy pregnancies, possibly reflecting suboptimal utero-placental circulation. Longitudinal studies examining comprehensively the predictive value of spiral artery Doppler for complicated pregnancies are yet to be carried out.

Doppler Flow Indices and Prediction of Embryo Transfer Success and Pregnancy Outcome in Uterus Transplant Recipients

“…20 Remodeling of the uterine spiral arteries is known to occur during normal pregnancy. 24,25 This is characterized by lower vascular resistance. We could find no data in the literature that describe vascular remodeling between successive pregnancies and how Doppler indices change from one pregnancy to the next in the same patient.…”

The feasibility of multimodality remote monitoring of maternal physiology during pregnancy

“…Importantly, cardiovascular parameters before, during, and after pregnancy do differ between healthy pregnancies and those affected by serious obstetric conditions, such as preeclampsia (PE), fetal growth restriction, or recurrent pregnancy loss. [10][11][12][13][14][15][16][17][18][19][20][21][22] It seems likely that there would be both research interest and clinical utility in measuring changes in cardiovascular indices throughout pregnancy at the level of an individual. Monitoring of maternal well-being could be complemented by home-based tracking of physical activity, sleep, weight, and surveying maternal mental health.…”