If a couple gives birth to a baby with a debilitating condition and dies after 6 weeks, that’s an additional baby death. If instead of having that baby, a couple gives birth to a healthy baby, it will likely survive into adulthood, meaning there’s one less baby death.

It sounds like you just take issue with abortion. That’s more of a you problem than a problem with quantifying baby deaths.

in some cases early and correct diagnosis saves lives. may not be applicable for the OPs situation, but imagine running full diagnosis is so cheap at some point in the future that every kid when they born get that diagnosis cheaply and automatically. And doctors do not need to "guess" based on symptoms.