Almost half the abortions that occur in North America are repeat abortions.
There are several factors. According to Fr. Frank Pavone of Priests for Life, pregnancy is a biorhythm (this is not New Age junk science.) Sleep is also a biorhythm. If you wake up in the middle of the night your body tells you to go back to sleep. Similarly many women who abort (an interruption to the biological process of pregnancy) feel the urge to get pregnant again.
Sometimes the same circumstances that caused them to abort in the first place are still present so they abort again. Sometimes the mother thinks she is unworthy of being a mother because she already aborted one child. Repeat abortions can be a sign of self-punishment.
And sometimes (and this is a big one) we repeat what we don't understand in the hopes of mastering it. This explains not only repeat abortions but why abused women stay with abusers, why some women keep sleeping around looking for love, etc.
Instead of being repulsed by the self-destructive behaviour of others ask them, "How can I help you to heal?"