Thanks for writing to HCM
Period may be delayed some time even in ladies who have history of regular periods,but if you have doubt ,she should go for urine pregnancy
Urine pregnancy test depend upon hCG
hormone in urine which is excreted only after fertilization of ovum.
Generally,Urine pregnancy test is done after missed period for confirmation of pregnancy,but Ultrasound
of pelvis is the investigation of choice for confirmation of pregnancy.It can detect G-sac earliest.
Hope i have answered your query.