It's awful if the long and short of it.
Best case scenario, small at birth, (assuming immediate fostering) about 6 - 8 weeks of constant pain, muscle spasms, sleeplessness and stomach problems, despite being dosed with morphine, then once the LOs system is clear, baby begins to grow, gain weight and develop at a normalish rate.
Worst case scenario, (assuming survival) born premature or severely disabled for life. High chance of heart weakness or respiratory problems through out life of child, or of inter-cranial haemorrhage which may cause stroke (again possibly leading to permanent disability) or death. Even if baby doesn't present with immediate disabilities, many things such as permanent brain damage or autism.
Truthfully, the average case is somewhere between the two. A baby born addicted certainly suffers from a painful, terrible first few months. More often than not has some serious SN for the rest of their lives and occasionally die
Offering to stop that happening by paying vulnerable women who (if they weren't using drugs and desperate) wouldn't want to do that to their own child doesn't seem terrible IMO.