This unblinded, randomized controlled trial (RCT) among women to determine:

1)if unprotected sex as measured prostate-specific antigen (PSA) will be more among women who receive a contraceptive implant immediately at baseline during three months of follow up compared to women who receive the implant at the three month follow-up visit.

This unblinded, randomized controlled trial (RCT) will assess whether the use of a contraceptive implant leads to more sex unprotected by a condom, as measured by the detection of a biological marker of exposure to semen in vaginal fluid, among women in Kingston, Jamaica.

Eligible women will be non-pregnant, not known to be HIV-positive, 18-44 years of age, not already using a long-acting method of contraception, without contraindications to implant use, and willing to use the Sino-implant (II). Eligible women will be recruited from the Comprehensive Health Centre Center of Excellence (CHC) in Kingston, Jamaica and from the community. Women who give written consent for study participation will be enrolled in the study and randomized to one of the two study groups: 1) "immediate implant" insertion or 2) "delayed implant" insertion (i.e., when their study participation ends after three months of follow up). All participants will receive safer sex counseling, will be supplied with condoms, and will be administered a baseline questionnaire on demographics, reproductive history and contraceptive and sexual practices. A study clinician will perform a pelvic examination during which a double-headed vaginal swab will be collected to be tested for prostate-specific antigen (PSA), which is a semen biomarker. Participants will be asked to return for follow-up visits scheduled at 1 and 3 months after enrollment, at which times they will have another double-headed vaginal swab collected during a pelvic examination for testing for PSA and will be administered follow-up questionnaires. Participants in the "delayed implant" group will have the Sino-implant (II) inserted at the 3-month visit if they still want the device.

Primary objective: To determine whether the frequency of PSA detection during three months of follow up is higher in the immediate implant group than in the delayed implant group.

Inclusion Criteria:

• Be willing to be randomized to receive the implant at the enrollment visit or in three months;
• Be 18-44 years of age;
• Not known to be HIV-positive;
• Have a negative pregnancy test at baseline;
• Not currently using an intrauterine device or system, a contraceptive implant, or injectable contraception;
• Not planning to start use an intrauterine contraceptive device or system or injectable contraception in the next three months;
• Not have had surgical sterilization or plan to have it in the next three months;
• Not have medical contraindication to implant use, including lactation within first 6 weeks postpartum, acute deep venous thrombosis or pulmonary embolism, lupus, migraine with aura, unexplained vaginal bleeding, current or history of breast cancer,severe cirrhosis, liver tumors, history of stroke, and current or history of ischaemic heart disease;
• Be willing to return to the clinic for two follow-up visits over the next three months; and
• Be otherwise a good candidate for study participation based on investigator assessment