This is typically a sign that the uterus is expanding very rapidly and typically either means a very large singular baby or two babies expanding the uterus combined. (checkpregnancy.com)
After an ultrasound — scheduled due to a rapidly expanding uterus or unusually high hormone levels detected in a blood test — identifies a multiple pregnancy, a follow - up ultrasound only detects one baby. (doctor-info.website)
There is also less space in the bowels from the ever expanding uterus; (lyndagriparic.com)