The effectiveness of Norplant implants over a seven year period of continuous use was studied in a multicenter trial. Pregnancy rates were 0.4 per 100 in both year six and year seven. More than 3,600 women completed 6 years and more than 2,400 women completed 7 years. Pregnancy rates increased with weight (p < .05) and decreased with age, but in years 6 and 7 combined, the pregnancy rate neither reached nor exceeded 1 per 100 woman years in any 5 year age group or in any 10 kg weight group.
PIP: The effectiveness of Norplant implants containing a total of 216 mg of levonorgestrel over a 7-year period of continuous use was studied in a multicenter trial. Enrollment continued from 1984 to 1987 with a cut-off in May 1994, by which time all women had completed 7 years of use. The subjects were 18-40 years old with at least 1 living child. More than 3600 women completed 6 years and more than 2400 women completed 7 years. There were 18 pregnancies in the 6th year and 12 in the 7th year. One of these was ectopic. The annual gross pregnancy rates were 0.40 per 100 in both the 6th and 7th year. For both years there was a significant difference in pregnancy rates among women in the different weight groupings (p 0.05), but not in the different age groupings. In years 6 and 7 combined, the pregnancy rate neither reached nor exceeded 1 per 100 woman years in any 5 year age group or in any 10 kg weight group. Only women under age 30 at admission who then weighed 65 or more kg had a pregnancy rate of 1.31 +or- 0.76 per 100 in the 6th and 7th years. No age-weight group had a pregnancy rate as high as 2.0 per 100 in the 2-year period beyond normal use. Cumulative life table pregnancy rates at the end of 5 years had been 1.53 per 100 for all subjects. At the end of 7 years the cumulative rate had increased by less than 1 per 100 to 2.32 per 100. The highest cumulative pregnancy rates were found among the women under age 25 and those weighing 70 or more kg at acceptance. The former group had a cumulative failure rate of 4.7 and the latter a cumulative rate of 6.6 per 100, respectively. This study provides evidence that Norplant implants remain a highly effective contraceptive method for a period of 7 years of continuous use.