Hiya
The term "Cervical Erosion" is completely misleading as nothing is actually worn away or "eroded". Normally the cells on the outer part of the cervix is lined with flat lining cells and the narrow passage through to the cervix is lined with narrow granular cells. Cervical erosion is completely normal and is simply the growing down of the narrow granular cells into the cervix, where the flat cells once were. Cervial erosion appears on the outer surface of the cervix to form a red, velvet-like area called a cervical erosion.
These cervical changes are a natural response to the female hormone, oestrogen, and can occur naturally in some women, during pregnancy, in those who have had children, and in women taking the oral contraceptive pill. Most erosions cause no symptoms. However, in some women they produce an increased mucus discharge. Occasionally the delicate cells may bleed easily when touched or during vigorous sex. As these cells are much more delicate than normal cells, this is most likely why your bleed at 16weeks has been attributed to the erosion.
Don't worry about it - Most women at some point in their life will suffer with varying degrees of Cervical erosion, but in most instances it will cause no problems. I've been aware of having cervical erosion since I was 19. At times I used to bleed after sex, but other than that I havn't had any major problems.
Hope this helps!