Hi lunavix
I had this with dd1. I bled at 27 weeks. Had had not inkling that anything was wrong at that time, as my hospital had a policy of not looking at (or, at least, not mentioning) the position of the placenta at the 20-week scan. I was hospitalised at 27 weeks and kept in for a week or so, as I kept bleeding on and off (it wasn't constant though ... more sort of odd lumpy bits... very very sorry if TMI). I was sent home after a week when things seemed to have stabilised, but I bled again that same night, so that was it - I was back in hospital for the duration then. DD1 was born by elective c-section at 36 weeks. She was small (even for a 36-weeker) at 4lb 12oz; I think because I'd lost bits of placenta along the way (the lumpy bits) so she was a bit undernourished. Nonetheless, she was otherwise fine. I'd had steroids weekly since my first bleed and she breathed absolutely fine on her own from birth. She had to be fed by NGT for about 10 days and I did have to leave her in hospital for about a week, which was absolutely the worst part of the whole thing. (I had to be discharged after a week, she was kept in until she could feed independently.) She had problems breast-feeding (though I was determined to do it) and I only managed to get her home feeding with nipple shields. Unfortunately, she wasn't gaining weight feeding like that, and after her 6-week check I changed to formula (reluctantly - but was more worried about her weight by that stage, as she was still under 6lb).
At 19 weeks there is plenty of scope for your placenta to move out of the way and for you to have a natural delivery. The placenta doesn't actually 'move' as such. The way it was explained to me was like if you stick a plaster on the side of a delated balloon. As you blow the balloon up, the plaster will seem to move up the side of the balloon, but really it'll be stuck on in the same place all along - it's just the balloon stretching. Your uterus is the balloon and the placenta is the plaster. As your uterus stretches, the placenta may well be lifted out of the way of the cervix and you'll be OK.
Placenta praevia is graded on a scale of 1-4. Grade 4 means that the placenta is completely covering the os (mouth of womb). This is what I had (they said my placenta was sunk in the cervix like a plug in a sink!) and it's the most serious as the most likely to lead to bleeding and also the least likely to move.
Definitely take the doctor's advice to avoid sex and lifting, and if it's shown that you do have placenta praevia then please do take it seriously. There is every chance that everything will be fine, and I really don't want to be alarmist, but if you do bleed again, and you know that you have pp then always go and get it checked out. It is very very unlikely, but if the placenta does become detached and you haemorrhage you don't have very long to get the baby out of there safely. This is why they wouldn't let me go home from hospital, even though I only lived 5 mins drive away. At the start I was desperate to discharge myself, but they wouldn't hear of it and they basically told my dh that I could bleed to death between my home and the hospital. However, this was after they had realised that my placenta was basically hanging by a thread. In most people's cases I don't think they are this alarmist about it.
When you go in, and if you do have pp, I'd be asking whether they think you should have steroids in case your baby has to be born early. They may say that this is unnecessary if your bleeding settles down and the pp is not too serious, but it's worth asking.
You should also ask whether they want to take blood from you to cross-match and save, just in case you do have a major bleed. Again, they may think that this is OTT. It may be something they only do in extreme cases. I had blood taken twice a week, just in case.
Like you, I didn't want a c-section, but if you do have total pp then there really is no other way. I can reassure you that an elective section is a really positive experience. Very calm, very relaxed and very joyful.
I hope that I haven't scared you. I wasn't sure how much to post here, but I've posted the same info elsewhere, so you'd have found it if you'd done a search... Please don't worry. I was told that I was VERY unlucky and that cases like mine are extremely rare. I hope that everything goes well at your scan and that you get some answers about the bleeding which are not too worrying. Loads of people have pp/low-lying placentas and some bleeding, but go on to have totally unproblematic deliveries. (I was one, with dd2... placenta was low-ish at 20 weeks and I had one very very small bleed, which freaked me out a bit as you can imagine, but the placenta 'moved' and I had a VBAC when I went into labour naturally at 37 weeks.)