From puberty onwards, depending on estrogen and activity levels, the hymenal tissue may be thicker, and the opening is often fimbriae of uterine tube or erratically shaped.
From the en.wikipedia.org
Menstrual extraction is essentially a vacuum-aspiration method in which the fertilized egg, if present, and the uterine lining are withdrawn by means of a tube inserted through the cervix.
From the time.com
Inserted into the uterus, they cause a minor inflammation of the uterine lining that prevents the fertilized egg from implanting in the uterine wall after its journey through the fallopian tube.
From the time.com
At that point the egg had moved from her fallopian tube and was floating freely, but it had not yet become implanted in the uterine wall, where there would have been more difficulty in removing it.