Babies do not have the awareness nor the muscle control necessary to display emotions. If that picture is legit (unlikely) it's merely a random shot of a random muscle pattern. If you capture a kid in utero with his middle finger extended it is not proof that babies are like teenagers and that he's flipping off his mother in advance. The fact is that the kid's features are randomly arranged and if you look at a given number of scans like that you're going to see smiles, frowns, sneers and at least one unborn wearing a rainbow wig and holding up a sign that says "John 3:16".
The people who see things like that as smiles are the same wannabelieves who see 747's as UFOs and think that Elvis is alive and working in a K-Mart in Des Moines. If you're anti-abortion, cool that's your right and I won't argue with it, but don't invent pseudoscience like this in an attempt to justify your beliefs, it's pure BS.