How do girls get pregnant on the pill so easy?

I've noticed alot of girls on Yahoo saying they got preg while on the pill. But I also read that the pill is at least 98% effective. So are they getting pregnant the 99th time they have sex, or are there other factors like being overweight, drinking/smoking, taking antiobiotics or just not taking em on the... show more I've noticed alot of girls on Yahoo saying they got preg while on the pill.

But I also read that the pill is at least 98% effective. So are they getting pregnant the 99th time they have sex, or are there other factors like being overweight, drinking/smoking, taking antiobiotics or just not taking em on the same day everyday?
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