Hi Welcome to HEALTHCARE MAGIC..
I have gone through your query and can understand your concern...
First of all chances of
pregnancy on
menstruation are less. Your girlfriend have also taken I-pill after that therefore pregnancy possibility should be less in her.
Delay in periods is a common problem after intake of an
emergency contraceptive pill like I-pill. The delayed periods are due to effect of high dose of
levonorgestrel hormone in I pill which disrupts normal menstruation & causes delayed periods. her periods may be delayed for 1-2 cycles.
An emergency contraceptive pill prevents pregnancy by inhibiting
implantation of fertilized egg on to uterus. It should be taken as soon as possible after having sex. It is 95% successful if taken within 24 hours of having sex. Its success falls to 70% if it is taken 24-72 hours of pill intake.
Next time use regular contraceptive pill or condoms for prevention of unwanted pregnancy.
You should also undergo a pregnancy test to rule-out pregnancy possibility, however chances of that should be very less.
Refer to a gynaecologist for more queries
Don't worry you would be fine