Prolonged effectiveness of Norplant(R) capsule implants: a 7-year study.
Soft tubing Norplant(R) contraceptive implants were studied in 1210 women for 7 years to measure the duration of effectiveness and the magnitude of the pregnancy rates over that time. Mean age at enrollment was 27.4 years. Of the enrollees, 42% were US residents. One-sixth (16.1%) weighed >/=70 kg at the time of implant placement. At the end of 5 years, the cumulative pregnancy rate was 1.1/100; at the end of 7 years, it was 1.9/100. No pregnancies occurred to any of the 400 women who enrolled in the study at age >/=30 years and who weighed <100 kg. Among women aged 18-33 years, the 7-year Norplant pregnancy rates are comparable to the median pregnancy rates of tubal sterilization methods for women of the same age and duration of use. For women aged >/=34 years, without regard to weight at admission, the 7-year effectiveness of soft tubing Norplant equals or surpasses that of tubal sterilization. For continuing implant users, annual pregnancy rates <1.0/100 in years 6 and 7, together with low cumulative pregnancy rates, testify that Norplant capsule implants remain highly effective for 7 years.
Sivin
I
I
Center for Biomedical Research, Population Council, New York, New York 10021, USA.
Mishell
D R
DR
Diaz
S
S
Biswas
A
A
Alvarez
F
F
Darney
P
P
Holma
P
P
Wan
L
L
Brache
V
V
Kiriwat
O
O
Abdalla
K
K
Campodonico
I
I
Pasquale
S
S
Pavez
M
M
Schechter
J
J
D000293:Adolescent; D000328:Adult; D001835:Body Weight; D003271:Contraceptive Agents, Female / Q000008:administration & dosage* / Q000009:adverse effects; D004343:Drug Implants; D005260:Female; D006801:Humans; D016912:Levonorgestrel / Q000008:administration & dosage* / Q000009:adverse effects; D011247:Pregnancy; D016016:Proportional Hazards Models; D013246:Sterilization, Tubal; D013997:Time Factors
D003271:Contraceptive Agents, Female; D004343:Drug Implants; D016912:Levonorgestrel