Women have to wait to conceive partly because injectables remain in the bloodstream for several months after the next injection would have been given. DMPA, for example, is detectable in the bloodstream for eight months on average after one injection (277).

There is no evidence that injectables cause infertility. In the Thai study 91% of former DMPA users had conceived within two years after discontinuing compared with 93% of former IUD users and 95% of former OC users. These differences are not statistically significant (236). By comparison, among US couples stopping contraception of all types, about 90% have conceived in 18 months, and about 10% of couples are infertile (351, 367). Amenorrhea may persist for several months after women discontinue injectables. Providers should warn women of this and reassure them that their regular cycles will return eventually.

Long-term users of injectables need not fear any cumulative impairment of fertility. There is no difference in the time to return of fertility between long-term and short-term users of DMPA (24, 87, 92, 235, 236, 277).

Despite this evidence, to avoid any possible blame for subsequent infertility, some programs have required women to have been pregnant at least once before allowing them to use DMPA. Such a policy restricts use unnecessarily. The McCormick Family Planning Program in Thailand followed this policy at first but removed it because of demand from women without children; indeed, some women lied about a previous pregnancy to be able to use DMPA. Following up these women after they stopped using DMPA, the program found no difference between their fertility and that of DMPA users who had had previous pregnancies (199).