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Its a known fact that ovulation occur 14 days of the menstrual cycleof 28 days.Firtilization is dependent on the ovulation as it occurs within 2-3 days.
SO if cycles are prolonged that is around 35-40 days then time of ovulation will be shifted as well as fertilization .
This is the probable cause of late detection of pregnancy
Your friend was having regular menstrual cycle of 28-30 days.
levels are within normal range.Congratulations , nothing to worry.
I hope this has solved your querry, if any doubt please contact .