This may not be the direction you want to go, but couldn't you fertilise eggs in vitro? The earliest pregnancy tests consisted of triggering frogs to lay eggs in isolation with the hormones from the woman's urine. Note I'm not suggesting that literally, but you may be able to identify conditions where that happens. Not sure how the male part would work, but if you can get him to mate at all, putting normal eggs in the same water may suffice.