Objective: To establish references ranges for the uterine arteries (UtA) Doppler and cervical length (CL) measurements at 11-13(+6) weeks of gestation in a Brazilian population.
Methods: We performed a retrospective cross-sectional study with singleton low-risk pregnant women who underwent first trimester ultrasound exams of fetuses with crown-rump length (CRL) ranging from 45 to 84 mm. The mean UtA Doppler and CL measurements were performed by transvaginal route. The mean pulsatility index (PI) of uterine arteries was obtained with color Doppler at the level of cervico-corporeal junction. The CL was obtained in a sagittal view using the cervical gland area as landmark. We determined mean ± standard deviation (SD), ranges for mean PI of UtA and CL in each gestational age. Polynomial regression was performed to establish reference values.
Results: We have assessed 598 first-trimester pregnancies: the CL measurement was obtained from 497, while the mean PI UtA Doppler was available in 450 pregnant women. The mean CL ranged from 33.41 to 35.58 mm while the PI UtA Doppler ranged from 1.89 to 1.45. The best fit curves were: CL = 30.790 + 0.057 × CRL and UtA PI = 2.411-0.011 × CRL.
Conclusion: References ranges for the mean UtA PI Doppler and CL measurement at 11-13(+6) weeks of gestation in a Brazilian population were established.
Keywords: Cervical length; first trimester; reference ranges; uterine Doppler artery.