A high incidence of cervical incompetence resultant from abortion has raised the incidence of spontaneous abortions to 30-40%. A. Kodasek, "Artificial Termination of Pregnancy in Czechoslovakia," Internat’l Jour. of GYN & OB, vol. 9, no. 3, 1971

Women who had one induced abortion had a 17.5% miscarriage rate in subsequent pregnancies, as compared to a 7.5% rate in a non-aborted group. Richardson & Dickson, "Effects of Legal Termination on Subsequent Pregnancy," British Med. Jour., vol. 1, 1976, pp. 1303-4

Women who had delivered their first pregnancy had (in the second pregnancy) the "best reproductive performance." Those who had a spontaneous miscarriage on the first had "the highest frequency of an early loss." Those with induced abortion on their first had "the highest frequency of late spontaneous abortion and premature delivery." Koller & Eikham, "Late Sequelae of Induced Abortion in Primagravida" Acta OB-GYN Scand, 56 (1977) p. 311.

What about second trimester losses?

There was a doubled incidence of midtrimester spontaneous losses. Herlap, New England Jour. of Med., no. 301, 1979, pp. 677-681