COVID-19 and antivaccine conspiracy theorists like Joe Mercola, Michael Yeadon, and Peter McCullough are spreading the conspiracy theory that COVID-19 vaccines are intended as a tool for "global depopulation". This is nothing more than an old antivaccine conspiracy theory repurposed for the pandemic. As ridiculous as it might seem, it is nonetheless very appealing to antivaxxers.
Antivaxxers have been claiming that vaccines cause female infertility for as long as I can remember. So it's not surprising that they are now claiming that COVID-19 vaccines will cause miscarriages or even make women infertile. Their assertion is based on a highly speculative and incredibly unlikely immunologic mechanism. Same as it ever was.