The only way to tell for sure is with a pregnancy test. Spotting and Cramping. A few days after conception, the fertilized egg attaches itself to wall of the uterus. This can cause one of the earliest signs of pregnancy -- spotting and, sometimes, cramping. That's called implantation bleeding.It occurs anywhere from six to 12 days after the egg is fertilized.The cramps resemble menstrual cramps, so some women mistake them and the bleeding for the start of their period.his can cause one of the earliest signs of pregnancy -- spotting and, sometimes, cramping. That's called implantation bleeding. It occurs anywhere from six to 12 days after the egg is fertilized.