It was very realistic to me. I started bleeding before I went into premature labour. It can be a sign that the cervix is opening.
Cervical stitches can (nowadays) be placed at around 15 weeks, or as an emergency later on. There is a risk of waters breaking during the procedure, I was expecting that story tbh. It seems that it was a fairly new thing in those days so it could be very different, but I'd like to think that she'd have an early stitch in future pregnancies and carry to term 
Very well portrayed to me.