This video has nothing to do with race, and it has nothing to do with her pregnancy. It consists of 2 former Jehovah's Witnesses pointing out the inconsistencies between JW teachings and Serena Williams' track record of supporting the LGBTQ+ community. Williams has recently been baptized into that denomination (after having been raised in it but not being an active member (link below), and these 2 ex JWs are disturbed by the discrepancy between her being a JW and being an strive LGBTQ+ plus supporter, as well as the things she will be expected to teach her children as an active JW.
I don't know if they actually say she "must" do this or that. The video is over 30 minutes long, and I haven't had time to watch the whole thing yet. (Also, from what I have seen, it's poorly made and therefore a bit of a slog to get through.)
I think what they are mainly trying to do here is educate people (including Williams herself) about some pretty despicable JW teachings that they used to embrace themselves but no longer do, and I support them in that aim, even though they may have gone about it a bit clumsily.
Edited to add this link: https://www.newsweek.com/what-serena-williams-said-about-being-jehovahs-witness-1773017