Calambo, you say you were raised in a christian background where abortion was off-limits. Did your wife come from a similar background? Whether or not she did, she must know about your background. Have you ever talked about abortion in her presence? Did you express any forceful views?
Abortion is not an easy option for a woman. Many find it traumatic. Some mourn for years or even a lifetime over the baby that could have been. In a social environment where it is politicised or religion comes into the issue, it must be almost imposible to talk about. She risks condemnation when what she needs is sympathy and understanding about the most horrible thing that has ever happened to her.
Maybe your wife copes by denial, or forgetfulness. Maybe you rescued her and helped her move on and establish a new life with new children. Maybe, even, you and your love and your (both) children redeemed her.
I think you should only raise the issue with your wife if you are ready to understand how she was at the time and empathise with her in retrospect. If there's even a hint of "she was bad to do that" or other disapproval in your mind, leave it alone. If all you're concerned with is "why did she keep a secret from me?" leave it alone. I'm sure there's some things in your life that you never thought to mention that might surprise her.
You found this out in a moment of her sister's drunken indiscretion. It might be best to convince yourself that that woman was deluded, mistaken, or had a subconscious reason to sow a seed of doubt into your relationship. It might not even be true!
It's so much easier for the guy, you'd think. My brother's girlfriend had a teenage abortion after non-penetrative sex! He'd only cum on her, not in her. I only heard years later, and our parents still don't know. Although of course, hers did, and supported her through it. Later on, a possessive girlfriend lied about her contraception, thinking a baby would seal their relationship (while they were in university!). She had the baby and he was adopted. Somewhere in Devon, there's a 25 yr old guy that's a blood relative of mine who knows nothing about his parents or relations. Hopefully he's had a good life and his adoptive parents have provided him with a good family background where he is loved and accepted for himself. Again, our parents do not know this. And you know what, I don't know whether his wife and mother of his two legitimate children knows this. I would NEVER, EVER take it upon myself to tell her, no matter how drunk I was.
Did you ever have unprotected sex with a woman before you married? You may have had an abortion or fathered a child outside of your marriage yourself, but just not know about it.
Lol, I only came here to look at the cocks! What has LPSG done to me?