Correct detection of premature contractions and incompetent uterine cervix is still a challenging obstetrical problem since these factors remain a major cause of perinatal loss. Ultrasonography offers additional important data for the prediction of these pathologies which have common sonographic patterns; shortening of the cervical length, funneling of the membranes and dilatation of the endocervical canal. The first section of this review highlights sonography of normal cervical anatomy, while the second section focuses on recent advances in sonographic detection of premature contractions and incompetent cervix. It is believed that due to its accuracy and reproducibility, this noninvasive technique should become more integrated into this aspect of antenatal care.