How big a selection pressure does higher IQ command? Wikipedia on Fertility and Intelligence:

Though many demographic studies have been performed, there is no conclusive evidence of a positive or negative correlation between human intelligence and fertility rate. Survival rates are, however, correlated with IQ, but the net effect on population intelligence is unclear.

Many local times & places have had a negative correlation between IQ and fertility.

Of course, fertility isn't precisely the same as inclusive fitness, but it's strongly correlated.

On the other hand, many women die in childbirth or suffer significant complications in many parts of the world even today.