Many congratulations - take some time to get over the shock, and surprise. You’ve done nothing wrong, and I know it was far from planned but it does complicate things quite a bit.
How long have your little ones been with you and how old are they? I can’t imagine any social worker wanting to disrupt placement because you’re pregnant, that would be way more harmful to your children than helping you support them through your pregnancy. I can however see any social worker worth their salt looking at the potential for the placement to break down regardless of everyone’s best intentions.
As a professional my concern would be you having the necessary physical, emotional and psychological resources to parent two small, traumatised children and a newborn. The potential is that the newborn takes priority because they’re the smallest, meaning the older children have to compete to have their needs met because all our resources are finite and in the best of circumstances new baby’s are a lot of work.
I’d start now thinking about how you’ll manage the competing demands of all your children whilst also recognising that a new baby may well trigger off all kinds of feelings (and behaviours) in your adopted children. One concern for social workers is that the adopted children become dysregulated, the parents can’t cope and begin to worry about the impact on the newborn (Eg if adopted children are triggered, become aggressive or violent towards the baby) with the result that the placement breaks down anyway. There are very good reasons for not placing children with parents who hope to conceive naturally, because 9/10 a parent will chose to protect their newborn, and the adoption breaks down usually with much heartache on all sides, but with very damaged children going back to the care system. I know that’s the furthest from your mind just now, but it’s far from an unusual occurrence.
In your case, there was no way to know that you’d become pregnant, and you’ve gone into adoption with ever good intention. I would however go against the advice to keep it quiet from social workers simply because you’re likely going to need their help even after the adoption order. You’ll need to consider what you’ll do if your children don’t cope, and what supports you might need. You’re not the first person it’s happened to and your social worker (or folk in their team) will have ideas about how to support you and your children. It’s very different to bringing a newborn into a bio family - and it sounds like your children are relatively recently placed (less than a year?), so the children won’t have a sense fully of being “family”. By way of example, my two were placed age 4 and 6, 3 years in and if we had to while my youngest would cope with a new addition, my oldest absolutely wouldn’t because she would always believe we love the new child better and much of her early years were spent not having her needs met in favour of younger siblings.
In these circumstances you need to give consideration not just to what you want, and what you hope for but what these little ones, that you’ve made a lifelong commitment to, can cope with too and what needs to be in place to help that.
It shouldn’t impact the adoption order being granted, but if you’ve got a court date and can wait to tell social work, that’s a decision for you to make. I know I’m being the voice of doom here (reinforcing all the “judges social worker” comments too boot) and I don’t want to cause you any upset or anxiety, but I want to be honest about why social workers might have concerns. Sometimes things work out really well but rarely without a lot of work, consideration and flexibility on all sides. I hope all goes well at the doctors and that you have a safe, healthy, happy pregnancy.