Can you ask the doc's office or even the doc who prescribed them? I wouldn't doubt the menstraul cycle couldn't be affected, many meds of this kind can have some minor to major affect on cycles. Missing periods only happened to mewhen I was anorexic, they stopped because I wasn't eating much, amny other nasty things happened then so I put the weight on, especially when I found I needed to get hormone shots to start my periods again, but I had to gain weight too, or it wouldnt work.
One a year my body would skipp a month but then get almost 2 a month, once for 21 days I just flowed.
I wasn't on any meds for depression or any mental disorders, so I couldn't attribute to that, even my doc didn't know what was happening, it just was way off but did adjust itself after awhile. If this is bothering you I would see the doc if I were you, relieve your mind of added stress.
Take care,
DE

In giving advice seek to help, not please your friend
SOLON