I was referring to the many instances in which the blastocyst does implant, but fails to grow past the initial stages of development. Progression to the point of differentiation of tissues is the hurdle that many fertilized ova fail to clear. Failure of implantation is still important to discuss in the political context given that there are so many people with an absolute absence of biology education that think that life begins at fertilization.
The issue comes from the fact that if there’s any amount of implantation and the very earliest stages of development, a pregnancy test will come back positive and there are many diagnostic tests (most imaging modalities) and many procedures (such as non-obstetrical emergency surgeries) that will get delayed or sometimes even denied because of the positive pregnancy test. Every AFAB that comes through an ER that might need imaging gets a point-of-care pregnancy test that has to come back negative for something like a CT scan unless it is a very dire situation because of the radiation risk to a developing embryo.
Obstetrical procedures like abortions are not the only ones that are gate-kept for AFAB patients because of the policies surrounding risks to developing embryos or fetuses.
Edit to add: The studies do say that the estimated incidence of clinically unrecognized pregnancies is approximately 20%, but given the myriad risk factors that can feed into that outcome, things like exposures, stresses, SES, and access to medical care may increase that incidence rate in some populations.