“The smarter the woman, on average the fewer children she will likely have. The result is a growing gender gap. Women will become increasingly less intelligent than men.”
That’s not correct logic. Women bear both male and female children in roughly equal numbers, so there won’t be any gender gap caused by this phenomenon, just increasingly less intelligent people of both sexes.
After researching this more I think you are right: smart women having less children will make both sexes less smart. This is doing major damage to average intelligence for all. A child's intelligence is more strongly correlated with the mother's. A smart woman married to a below average IQ man can have smart children, but a below average woman married to a smart man is much more likely to have below average IQ children. Smart women having fewer children is having a profound impact on our children's intelligence.