I am pro-choice, because it's eugenic and prevents unwanted pregnancies to lower IQ unwed mothers. The babies born would, on average, have worse childhoods than if they were wanted and planned around, with a greater chance of growing up in a broken home and engaging in crime. This is the case with or without factoring in ethnicity.

On the subject of declining overall birth rates, the main culprit I would examine is wage stagnation relative to inflation, and the preoccupation of women with careers. Simply put, babies are too expensive and prospective mothers have other life priorities, on top of contraceptive access and whatever self-interested anti-natalist cultural influence is at work.

Declining birth rates are a problem because our whole economic system is structured around high sustained growth and the expectation that younger generations will always be there to replace the increasingly burdensome older ones in the workforce. You might also realize why immigration is such a desirable thing to traitorous politicians, regardless of the impact on crime, economic opportunity for existing citizens, and culture/ethnic composition.