Anovulation, inadequate luteal phase and poor sperm penetration in cervical mucus during prolonged use of Norplant implants.

Blood samples for progesterone assay were collected for a total of 49 cycles, from 27 volunteers using the NORPLANT system. Levonorgestrel determinations were carried out in the same samples. A group of 12 women with normal cycles were studied in the same manner to serve as controls. Of the 49 cycles studied, 20 (41%) were ovulatory. The mean levonorgestrel level in ovulatory patients was 0.34 +/- 0.11 ng/ml (S.D.) compared to 0.42 +/- 0.14 ng/ml (S.D.) in anovulatory cycles. Compared to the control group, progesterone levels were significantly lower for users of NORPLANT implants during days -12 to -10 (p less than 0.025), -9 to -7 (p less than 0.05), -6 to -4 (p less than 0.0005) and days -3 to -1 (p less than 0.01). Cervical mucus evaluations and post-coital tests were done around mid-cycle in 29 of the cycles studied. All samples of cervical mucus were of poor quality, viscous and scarce, with a mean SPK of 4.1 +/- 2.3 cm. Most had absent or atypical ferning. Twenty-one subjects (73%) had a post-coital score of 1, and 4 (14%) of zero. Thus, anovulation, inadequate luteal phase and the direct effect of the continuous administration of levonorgestrel over cervical function, all seem to contribute to the effectiveness of NORPLANT implants.