As soon as conception happens, then you've got a zygote which is very likely to make it to live birth.

From the NIH:

It is estimated that up to half of all fertilized eggs die and are lost (aborted) spontaneously, usually before the woman knows she is pregnant. Among those women who know they are pregnant, the miscarriage rate is about 15-20%. Most miscarriages occur during the first 7 weeks of pregnancy. The rate of miscarriage drops after the baby's heart beat is detected.

So your bright line should be heartbeat, or at least zygote implantation. This does not significantly affect your conclusions.