The study aims to explore the efficacy and safety of an intravaginal acetic acid thermoreversible gel in Chinese women of reproductive age, comparing it with nonoxinol gel by assessing the six-month Pearl Index and the incidence of any side effects.

Despite significant increases in the availability and effectiveness of contraceptives globally, there are few female-led devices that combine contraception and STI prevention. Previous studies suggested that acetic acid thermoreversible gel, a female targeted contraception, can regulate intravaginal ph, killing sperm and STI pathogens and protecting intravaginal probiotics. Therefore, we have developed a contraceptive gel containing 11.23 mg/g of poloxamer 407-acetic acid. To determine its contraceptive effectiveness and safety compared with the widely used nonoxinol gel, we will recruit about 240 reproductive-aged women in four centers in China and randomly allocate into two groups. During a six-month follow-up, we will compared their pregnant rates and incidence of adverse events.

Inclusion Criteria:

• 1) Aged between 20 and 45 years old;
• 2) Regular menstrual cycles (cycle length 25-35 days, menstruation lasting up to 7 days);
• 3) Have a history of pregnancy with the current partner at least once;
• 4) Currently engaging in regular sexual activity and planning to do so in the next six months (at least once a week);
• 5) Have not used hormonal contraceptive methods in the past 3 months;
• 6) Normal menstrual cycles have resumed after the removal of an intrauterine device;
• 7) Normal menstrual cycles have resumed after a previous miscarriage;
• 8) Breastfeeding women with normal menstrual cycles resumed;
• 9) No apparent gynecological abnormalities confirmed through examination, and normal cervical cytology (Pap smear grade I according to the Bethesda system);
• 10) Reliance on the investigational drug as the sole contraceptive method during the study period;
• 11) Willing to participate in this study, adhere to required follow-up visits, and voluntarily sign the informed consent form.

Exclusion Criteria:

• 1) Amenorrhoea for more than 1 month, suspected pregnancy;
• 2) Moderate to severe erosive changes in the cervix;
• 3) Vaginal cleanliness grade III or above;
• 4) Trichomonas, fungal vaginitis, and bacterial vaginosis, among other conditions, have not been cured;
• 5) Uterine prolapse of degree II or above and severe protrusion of the anterior and posterior vaginal walls;
• 6) Unexplained vaginal bleeding;
• 7) Genital tract deformities;
• 8) Malignant tumors of the genital tract;
• 9) Moderate or severe urinary incontinence;
• 10) Recurrent urinary tract infections;
• 11) History of allergy to acetic acid and/or nonoxinol.