Implant Timing and Replacement

Implants can be inserted at any point in the cycle and at most points after pregnancy, provided pregnancy is reasonably excluded. Protection is immediate when insertion falls within 7 days of the start of menstrual bleeding or in another situation where ovulation has not yet resumed; otherwise a backup method is needed for 7 days. Replacement timing depends on the system, not the class.

Device lifespans.

Basis of the 7-day rule. Progestin needs about 7 days to thicken cervical mucus and suppress ovulation reliably when inserted after ovulation may already be developing.

Effectiveness. About 0.05 pregnancies per 100 women in the first year once correctly started.

Return to fertility. Fertility returns within weeks of removal, so a gap between removal and a new method exposes the patient to pregnancy at once.

Reasonable certainty of non-pregnancy. No signs or symptoms of pregnancy and one of: no intercourse since the last normal menses; correct and consistent use of a reliable method; within 7 days of the start of normal menses; within 4 weeks postpartum; within 7 days after abortion or miscarriage; fully or nearly fully breastfeeding, amenorrhoeic and under 6 months postpartum.

When a pregnancy test is needed. When none of these criteria is met. A negative urine test is reliable only if there has been no unprotected intercourse in the previous 3 weeks.

Quick start. If pregnancy cannot be excluded but the risk is low and the patient wants to start now, the implant can be inserted with backup 7 days and a repeat pregnancy test in 3 to 4 weeks. Implants carry no known risk to a pregnancy.

Eligibility at initiation. Category 2 in breastfeeding under 6 weeks postpartum; category 1 for non-breastfeeding postpartum and postabortion patients. Current breast cancer remains category 4 in every situation.

Counselling. Tell the patient whether she needs backup and for how long, the replacement date, and that removal is available at any time.

Start timing.

Switching.

Replacement.

• Replace at or before the end of the lifespan through the same incision, with no gap and no backup.

• Early replacement is always acceptable.

• If replacement is late, assess intercourse since expiry, exclude pregnancy, replace and use backup 7 days unless within 7 days of the start of bleeding.

• With continuing enzyme inducer or efavirenz use, condoms remain necessary throughout the new implant's life.

Postpartum documentation. Record breastfeeding status and the date of insertion relative to birth.

Failure from timing errors. Most pregnancies attributed to implants follow insertion when conception had already occurred. Where risk existed at insertion, arrange a pregnancy test at 3 to 4 weeks.

Pregnancy discovered after insertion. Exclude ectopic pregnancy. Remove the implant if the pregnancy continues; there is no known foetal harm.

Overdue implant with pregnancy. Remove the implant and manage the pregnancy; counsel on the cause.

Bleeding after early postpartum insertion. Bleeding may be prolonged in the first weeks; distinguish lochia, retained products and infection before attributing it to the implant.

Red flags. Pelvic pain with a positive pregnancy test, heavy bleeding after postabortion insertion, signs of uterine infection.

Referral and escalation. Refer suspected ectopic pregnancy and postabortion sepsis urgently.