I also have Anti RO/SSA and SSB antibodies (lupus) and this was my experience with it. Hope it helps, and maybe you can compare it with what doctors recommend for you. It also depends on the titer/level of antibodies, mine were fairly high so they wanted to keep a close eye on things :/.
The main danger is that Anti-ro antibodies cross the placenta and can accumulate in the AV node of the baby's heart. This affects the electrical signals, so affected babies have heart problems or may need a pacemaker after birth. The risk is highest between weeks 18-24 (most specifically 19-22) where the heart is still maturing. So between weeks 16-24 I had weekly ultrasounds to check the heart rate and speed at which signals pass between the chambers. I had alternating appointments between prenatal and fetal cardiology departments. The red flag is brachycardia, which is a slowing down of the heart rate (normal is between 120-180 bpm, in some cases of anti-ro heart block the rate can be as low as 50-60 bpm). If everything looks fine at 24 weeks, then the heart is already mature enough and the anti-bodies no longer pose a risk. I just had my 24th appointment last week and breathing a huge sigh of relief since everything was ok.
If they find a problem with the heart rate, there is still treatment which is a form of dialysis where they literally "wash" the antibodies out of your bloodstream. My rheumatologist was adamant that, based on latest research, steroids do not work as treatment (as this is sometimes used depending on hospital). The best prevention you can do yourself is to take Plaquenil/Hydrochloroquine daily which has also been proven in a recent study to protect unborn babies against heart block. I was taking this already and they increased my dose as a result of the antibody test. It's perfectly safe in pregnancy but obviously please talk to your rheumatologist about it.
The actual risk for heart block is 3-5% which is fairly small. I found a reassuring article saying that the overall chance of any birth defect in pregnancy is 3-5%, so literally every person goes into pregnancy with that a baseline risk. It feels scary but make sure you have a good doctor who takes you seriously and can arrange the right check-ups between 18-24 weeks. They should be weekly, not fortnightly. Fortunately you're still early in the pregnancy so you have a bit of time to sort out checkups and medication if needed :)!
Sorry to hear about how stressful your first two births were. I don't think Anti-Ro is specifically related to pre-eclampsia but lupus definitely raises the risk. I was also prescribed low dose aspirin (100mg) against pre-eclampsia. I currently take 200mg Hydrochloroquine and 100mg Aspirin daily. I had weekly heart scans for the baby between between weeks 16-24 at Prenatal and Fetal Cardiology, and monthly bloodwork at Rheumatology (every month until birth). I was also tested for anti-phospholipid antibodies and lupus anticoagulant which are also common in lupus patients and can cause potentially serious clotting issues. Luckily mine were negative, but if I had them, then I would have had to add heparin (blood thinning) injections every day throughout pregnancy.
Really hope this helps and wish you a smooth & healthy pregnancy!