In case anyone else is interested, I did a literature search on fertility following adoption. (See
discussion in previous post.)
American Journal of Obstetric Gynecology
says no, or did in 1979. Journal of Psychosomatic Medicine (perhaps unsurprisingly)
questions the validity (pdf link) of many past studies.
I'm not utterly convinced. It seems likely to me that for certain specific causes or types of infertility, adoption or taking care of children may have a significant effect on fertility (probably female fertility).