The 33-year-old former Little Mix star is expecting twins with her boyfriend Zion Foster, 25, but was rushed to hospital after it was discovered her twins were at risk of dying as doctors uncovered they were "living off one placenta" and the singer required surgery.
Marking Mother's Day in the UK on Sunday, Nelson took to Instagram to share a video message with fans alongside Foster.
She revealed, "We just wanted to give you guys an update, as we know it's been a while. I don't know if you can see, but we are still in hospital, I've been recovering, but we have some amazing news.
"The TTTS (twin-to-twin transfusion syndrome) has cleared up; the operation was a success, which is just absolutely incredible. We are so, so lucky to have the most amazing doctors."
She continued, "Basically, the situation we're in now is my cervix is very, very short, so I can't leave the hospital because my waters could break at any point and I'm still very, very early.
"I can't leave the hospital until I'm a certain amount of weeks, so every week we're just like, 'Please, please, please, stay in there!'"
Foster added, "One week at a time, but we're in such a blessed position to even be able to make this video" - while Nelson added she and her partner are "so grateful" to learn their unborn children are "going strong".
