DMPA is efective, and as with other progestin-only methods, contraception is provided by ovulation inhibition, greater cervical mucus viscosity, and creation of an endometrium unfavorable for ovum implantation. Initial injection is given within the irst 5 days following menses onset. Serum levels suicient for contraception are observed by 24 hours. Thus, no additional contraceptive method is required for initiation within this window. Alternatively, limited data support a "quick weart," or initiation of DMPA regardless of cycle day. If so implemented, investigators recommend an initial negative pregnancy test result before injection, a supplemental contraceptive method during the 7 days following injection, and a second pregnancy test after 3 to 6 weeks to identiy an early pregnancy (Rickert, 2007; Sneed, 2005). Pregnancies conceived during DMPA use are not associated with a higher risk of fetal malformation (Katz, 1985). For women who present for intramuscular DMPA reinjection more than 13 weeks or for subcutaneous DMPA reinjection more than 14 weeks ater the prior dose, the manufacturer recommends exclusion of pregnancy before reinjection (Pfizer, 2015a,b).
Injected progestins ofer the convenience of a 3-month dosing schedule, contraceptive eicacy comparable with or better than COCs, and minimal to no lactation impairment. Irondeiciency anemia is less likely in long-term users because of amenorrhea, which develops in up to 50 percent after 1 year and in 80 percent after 5 years.
Similar to other progestin-only contraceptive, irregular menstrual bleeding is common, and a fourth of women dis continued DVIPA in the irst year because of this (Cromer, 1994). Unique to DMPA, prolonged anovulation can follow discontinuation, which results in delayed fertility resumption.
After injections are stopped, a fourth of patients do not resume regular menses for up to 1 year (Gardner, 1970). Accordingly,
DMPA may not be ideal for women who plan to use birth control only brieRy before attempting conception.
As with other progestins, DMPA has not been associ ated with cardiovascular events or stroke in otherwise healthy women. However, in those with severe hypertension, a higher risk of stroke has been found in DMPA users (World Health
Organization, 1998). Moreover, the US MEC authors express levels from DMPA in women with vascular disease or multiple risks for cardiovascular disease.
Weight gain is generally attributed to DMPA, and these increases are comparable between the two depot forms (Bahamondes, 2001; Vickery, 2013; Westhof, 2007c). In long-term users, loss of bone mineral density is also a potential problem (Petitti, 2000; Scholes, 1999). In 2004, the FDA added a black box warning to DMPA labeling, which notes that this concern is probably most relevant for adolescents, who are building bone mass, and perimenopausal women, who will soon have increased bone loss during menopause. That said, World Health Organization (1998) and American College of Obstetricians and Gynecologists (20 16b) believe that DMPA should not be restricted in those high-risk groups. And, it seems prudent to reevaluate overall risks and beneits during extended use. It is somewhat reassuring that bone loss appears to be reversible after discontinuation of therapy, although reversal is still not complete after 18 to 24 months (Clark, 2006; Scholes, 2002).