Combined oral contraceptives (COC) are a very popular form of birth control. Incorrect use and lack of adherence to treatment reduce the effectiveness of this method. Having a standard tool to identify poor-adherence profiles quickly and objectively can be helpful for midwives and potentially for COC users. The MMAS-4 adherence scale has been used in various medical fields, but there is little evidence of its potential in contraceptive consultation. This paper presents a piece of multicenter observational research based on a sample of 327 women who had attended contraceptive counselling in Spain and were COC users or had informed the midwife that they want to start to use this method. Two interviews were conducted: at the time of consultation and after one year. In our research, the MMAS-4 identified high-risk behaviors: during the 1-year follow-up period, COC users classified as poorly adherent had a significantly higher risk of missed contraceptive pills, more incidents and problems related to the method of contraception, as well as a lower degree of satisfaction with the contraceptive method. One case of unplanned pregnancy and two cases of emergency contraception were identified, all of them corresponding to poorly adherent women. The use of MMAS-4 in consultation can improve midwives’ contraceptive counselling.