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Background: Hydraulic dilatation is a novel method of cervical dilatation that is based on continuous controllable dilatation (CCBD) by the pumping of fluid into the balloon extension of the system. The main advantage of this procedure is that it allows control of and insight into the process of cervical dilatation.Methods: For the purposes of our research, we created a new and upgraded system for CCBD which consists of a programmed hydrostatic pump connected to a balloon extension. With regard to our aim to precisely measure and determine the location of the cervical resistance, we placed two pressure-measuring films, one on the top and one on the bottom of the balloon extension. This study included 42 patients in whom cervical resistance was measured before suction curettage.Results: Cervical dilatation and measurement of cervical resistance were successful in all patients. The analysis of the pressure-measuring films showed that the points of highest resistance were located in the zone of the internal cervical os and that these values were much higher than those in the zone of the external cervical os (0.402 versus 0.264 MPa at the upper pressure-sensitive film; 0.387 versus 0.243 MPa at the lower pressure-sensitive film). This study also showed that an increase in cervical resistance in the zone of the internal cervical os was followed by an increase in cervical resistance in the zone of the external cervical os.Conclusions: During CCBD, the internal cervical os is the centre of cervical resistance, and the values do not decline with the number of miscarriages or the number of previous births.Trial Registration Number: ISRCTN Registry identifier: ISRCTN30949871 . Date of registration: 13 May 2015. [ABSTRACT FROM AUTHOR]

Background: Cervical dilation using mechanical dilators is associated with various complications, such as uterine perforation, cervical laceration, infections and intraperitoneal hemorrhage. To achieve safe and painless cervical dilation, we constructed a new medical device to achieve confident mechanical cervical dilation: a continuous controllable balloon dilator (CCBD)., Methods: Controlled pumping of incompressible fluid into the CCBD increases the pressure and outer diameter of the CCBD, continuously dilating the cervical canal. The reliability of the CCBD was confirmed in vitro (testing for consistency and endurance, with no detected risk for breakage) and in vivo. A multi-center clinical study was conducted,with 120 pregnant women randomly assigned to one of three groups: Group I,control group, no dilation;Group II,mechanical dilation, Hegar dilator (HeD); and Group III,CCBD. The tissue material for histological evaluation was obtained from the endocervical mucosa before and after dilation using the HeD or CCBD., Results: The CCBD dilations were successful and had no complications in all 40 patients of Group III. The cervical tissue was markedly less damaged after CCBD dilation compared with HeD dilation (epithelium damage: 95% (HeD) vs. 45% (CCBD), P <0.001; basal membrane damage: 82.5% (HeD) vs. 27.5% (CCBD), P <0.001; stromal damage: 62.5% (HeD) vs. 37.5% (CCBD), P <0.01). Cervical hemorrhagia was observed in 90% of the patients after HeD dilation versus in 32.5% of the patients after CCBD dilation., Conclusions: The CCBD should be used as a replacement for mechanical dilators to prevent uterine and cervical injury during cervical dilation., Trial Registration: ISRCTN54007498.