If hCG levels rise slowly after implantation, it may not be an indicator of a viable pregnancy. The hCG hormone is typically produced by the placenta shortly after implantation and its levels should rise rapidly in the early stages of pregnancy. Slow rising hCG levels can be an indicator of a miscarriage, ectopic pregnancy, or other medical issues. However, if the hCG levels are rising slowly but consistently, it could be an indication of a healthy pregnancy, although further tests may be necessary to confirm this.