Edelman D A, Zipper J, Rivera M, Medel M
Contraception. 1979 May;19(5):449-54. doi: 10.1016/0010-7824(79)90060-x.
The relationship between the time in the menstrual cycle when a TCu-200 or Cu-7-200 is inserted and subsequent IUD-related events was evaluated. For women who had either TCus or Cu-7s inserted, the pregnancy, expulsion and medical removal rates were similar for insertions performed at any time of the menstrual cycle.