The biomechanical evolution of the uterus and cervix and fetal growth in human pregnancy

The coordinated biomechanical performance of maternal tissues facilitates healthy pregnancy. Quantifying uterine and cervical biomechanical function has been challenging due to minimal data on the anatomy's shape, size, and material properties across gestation. Addressing this challenge, this study quantifies structural features of human pregnancy by assessing maternal reproductive tissues and estimated fetal weight in 47 low-risk pregnancies at four gestation times. Uterocervical size and estimated fetal weight were measured via ultrasound, and cervical stiffness was measured via mechanical aspiration. Patient-specific uterocervical solid models were built for each time point, and uterocervical dimensions and cervical stiffness rate changes were assessed between time points. We found that uterine growth rates are time- and direction-dependent, with cervical softening occurring fastest in early gestation and cervical shortening fastest in late gestation. In conclusion, this work enables computational modeling platforms (i.e., digital twins) to explore the structural performance of the uterus and cervix in pregnancy.