Well it’s generally nothing to do with your bladder and everything to do with your pelvic floor. Most women might experience leaking during and after pregnancy. It is a lot more common than people think may think, especially after pregnancy.
It can be very common in the third trimester because of the pressure from the uterus on the bladder. Adding to the problem is the change in hormones, needed to make your tissues and joints more elastic for delivery. They can also reduce bladder support, allowing urine to leak.
About two-thirds of women with stress incontinence also experience urge incontinence, which is caused by an overactive bladder. You get the sudden urge to go, even though your bladder may be nearly empty, and leak before you can get to the bathroom.