Assessment of luteal blood flow in normal early pregnancy.

A cross-sectional study was performed in 85 low-risk singleton first trimester pregnancies to assess corpus luteum blood flow during this period. Gestational age, established by measuring crown-rump length, ranged from 6 to 12 weeks. All cases were studied by transvaginal color velocity imaging and pulsed Doppler ultrasonography. After corpus luteum blood flow was identified by color velocity imaging, the resistive index and pulsatility index were calculated to assess vascular resistance. Overall, detection rate of corpus luteum blood flow was 75.2%. No statistical differences were found in mean resistive index and pulsatility index among gestational weeks studied. Linear regression analysis showed that nonsignificant changes in resistive and pulsatility indices occur during the first weeks of normal early pregnancy (R2 = 0.0059 for resistive index, R2 = 0.0008 for pulsatility index). In conclusion, luteal blood flow is constant during normal early pregnancy.