Unplanned pregnancies and the pill.

PIP: In the past 3 months, I have had 7 patients referred to me with unplanned pregnancies, all having occurred while on 2 low-dosage preparations containing levonorgestrel and ethinyl estradiol (Nordette and Microgynon 30). From the patients' histories it appeared that there was no evidence of patient error, but the 1 common factor was that all the patients weighed in excess of 59 kg. It would appear that these low-dosage preparations should be carefully monitored in patients such as these, as it seems there is a dose-weight relationship.^ieng