Presumably high-quality studies would be those that are large AND have a large control group of women of comparable age and socio-economic profiles, who had unwanted pregnancies, considered abortion, but ultimately decided against it. The reality is that women who have unwanted pregnancies are disproportionately suffering from various psychological/psychiatric problems to begin with, which is why they’re unable or unwilling to reliably obtain and use contraceptives.
That makes sense to me. Over the years, I have learned that several of my relatives, friends and acquaintances have had abortions. (People confess this kind of stuff to me; heaven knows why.) Invariably, their lives are messed up. They were messed up before the abortions, and they remained messed up after the abortions. The only two that seemed to get over the guilt and pain were two women from my church who became Christian, and experienced Christ’s forgiveness.
I know this literature and if you want to educate yourself on it I'd direct you to the Association for Interdisciplinary Research on Values and Social Change. They have a data base and archived studies and a newsletter summarizing current research, which will provide all the information you need to become competent in the area.