Advice or experience of SGO of newborn

[Welsh1]

My niece and nephew (age 10 and 12) were placed with my parents a few years back under an SGO due to emotional abuse and drug/alcohol issues of my sister (their mother). My sister is now pregnant again (father of this new baby is not known). She is awaiting detox and rehab and was previously informed by social services any future pregnancies would result in the child being taken at birth. My parents do not feel they could take on a newborn baby but myself and my husband feel we would be in a position to (we have a 5 and 2 year old). However I'm struggling to find out any information on what happens in this situation- most of the things we've read is about children already born being placed away from their biological parents. What can we do to prepare and as I would need to take leave from work in the first instance would there be any financial support or would it be 18 weeks unpaid leave as per advice I've read? I feel we'd need to have legal parental responsibility to offer some security to us as well as the child?would an SGO be the best option? If the child were to have any disability or developmental issues due to my sisters continued drug and alcohol use in her pregnancy so far, what support would be available and our other concern is the impact on our niece and nephew and own children. Does anyone have any advice or experience in this area?