I have a 19-month-old that was weaned fully at 18 months. I became pregnant again when he was about 11-months-old. This pregnancy was a total surprise, a good one, but I obsessed for months on what I was going to do with trying to nurse 2 kids, because my son was nowhere near giving up nursing at a year. Nursing while pregnant was not an issue at all for me, in fact, I think it actually helped the nausea at first. It also forced a bit of quiet built into the day. All that said, obviously did not want to be nursing 2 kids, and dealing with jealousy issues that could arise because of it.
At 15 months, I started by giving up nursing him ever during the day (in theory, I was nursing only at bedtime and during the night and in the morning, but really, there were other times too, if he happened to want it.) The next thing was to make it a personal policy to never put him down sleeping. This was a challenge, and there were a few tears, but, not many and I never let the tears get out of control. I just started detaching him right before he would drift off and get him to the crib. At first, he would start fussing and really have an issue with it... but he eventually figured it out. It took about 1-2 weeks to get him comfortable with that... and I still put him down sleeping the 3 days during the week that I have him for naptime (that he's not with a sitter.) All said and done... that was the hardest part. Weaning fell in line after that. I stopped nursing in the morning by making sure that breakfast was ready when he woke up (and he was usually hungrier in the morning than nursing could satisfy, anyway.) Then, I stopped the nighttime feedings. Those went away within about 2 weeks. At first, I just stopped feeding every time. I'd go in and pick him up and hug him for awhile, maybe sit and rock with him, then put him back down. He didn't understand at first, but never made a huge ruckus. If he did make a huge ruckus, I'd pick him back up, because I can't handle ruckus at 2 a.m. I started only feeding once at night... then he kind of naturally stopped doing that. He started preferring to just be held really closely. He started detaching himself at this time during the bedtime feeding. He'd just want to be held for awhile. I think the thing that helped was that he started associating behing held really closely with sleep and comfort, instead of nursing. That's the key... to get him to not associate nursing with calming down and drifting off. It took 3 months with my son. We went very slowly. But, in the end there were next to no tears associated with this process and I think it was about 2 or 3 weeks before he realized he was no longer nursing, and actually wanted to start again. But, that was nothing. So far, so good with him. I wish it had been quicker, but honestly, nothing could've been more gentle for him. And this is a boy who was extremely attached to nursing.
So. Good luck. Be blessed. Make sure that your little one knows, though, that you are making the decisions regarding this, if that makes any sense.