Background: Fetal hemodynamics can be assessed by Doppler ultrasonography, but the normal Doppler waveform pattern and reference range of fetal renal artery blood flow indices in normal Thai fetuses during the second trimester have not been studied. Objectives: To study the pattern and establish the normal reference range of fetal renal artery blood flow indices in the normal Thai fetus during the second trimester. Materials and methods:This cross-sectional descriptive study included 512 normal singleton pregnant women, gestational age between 14 (+0) and 28 (+6) weeks. Ultrasonography was performed to assess the Doppler waveform pattern and estimate the normal reference range of fetal renal artery blood flow indices. All fetuses were delivered at term with normal outcomes at birth. The mean and 95 th and 5 th percentiles of the Doppler indices for each gestational week were estimated. Results: Doppler patterns with absence of diastolic flow in the entire cardiac cycle (type I), and absence of diastolic flow at the end of cardiac cycle (type II) were presented in about 10.4% of normal fetuses during the second trimester of pregnancy. Values for pulsatility index, peak systolic velocity, systolic-to-diastolic ratio, and resistance index (with absent end-diastolic velocity (AEDV) removed) each increased significantly with gestational age. The increase in end-diastolic velocity (with AEDV removed) with gestational age was not significant. Conclusion: These normative data could serve as a basis for evaluation of the fetal renal artery blood flow, which should be of benefit for pregnancy management, especially in situations that interfere with fetal renal perfusion.
A prospective study was conducted for comparing the incidence of fetal bradycardia and level of fetal heart rate change following a second-trimester genetic amniocentesis with and without placental injury. A total of 257 and 495 participants in injured and non-injured groups were analysed. The incidence of fetal bradycardia following amniocentesis was not statistically different between the two groups (1.17%, [95% CI 0.24, 3.37] and 0.20%, [95% CI 0.005, 1.12]) in injured and non-injured placenta groups, respectively; p = 0.118). The mean change in baseline fetal heart rate before and after amniocentesis was also not significantly different between the two groups (p = 0.844). No fetal death or pregnancy loss occurred within 4 weeks after the procedure. All 4 bradycardia participants were normal and healthy and had an appropriate weight for their gestational age. We conclude that placental injury during a second-trimester genetic amniocentesis due to advanced maternal age poses only a low risk of fetal bradycardia, and there is no evidence of differences between subjects with injured and non-injured placenta in the changes in fetal heart rate.
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