Babies in utero can be subject to child protection plans, especially in cases of domestic violence, previous child abuse convictions, severe mental health issues (eg psychosis) and drug and alcohol abuse.... (Hopefully any child protection social workers reading this maybe able to clarify the legal parameters more clearly....?)
It's been a good 5+ years since I worked in HV (but I can't imagine it's changed that much in this respect).... But was aware of several babies-in-utero subject to child protection plans. Such as babies due to be removed at birth and placed in foster care or those babies who had to go straight to NICU for heroin withdrawal management.
I don't agree that people should 'mind their own business' in these situations, child protection is everyone's business.
GCHQ good for you for having the courage to do something, that must have been hard.
OP if you are genuinely concerned about the large amount of alcohol you say you know is being consumed there are things you can do. Most counties have child protection phone lines you can call and leave information about concerns. Or you can contact the local midwives and ask them to pass the information onto the relevant community midwife and health visiting teams. You will need to provide some identifying information like her full name and dob or address so they can find her on the system. I think usually you don't have to give your name if you are worried about doing this.
The reasons I would do this is so that the authorities can determine the level of risk here. Her midwifery team may be unaware of her drinking. This can have implications for her health during pregnancy and they will ensure she gets the appropriate level of monitoring. They can also refer women to prenatal support groups and health promotion programs- they have specialist midwives who deliver these.
They may also liaise with her HV team after the baby is born who may wish to carry out extra development checks on the baby or refer to a Paediatrician.
You could be helping to ensure that this potentially vulnerable pregnant women and her baby were getting the support that they may need.
such a difficult situation all round