Pregnancy before marriage is extremely common in Poland. But usually the couple manages to get married before the baby is born.
and the guy is a total loser
This is why young ladies used to have chaperones. Left to their own judgement (which is poor due to limited experience and surging hormones) young women tend to pick.... total losers (the bigger the loser the harder they're likely to fall). This is why young women usually had chaperones around them who could sniff out the losers and scare them off.
Back to your question. It happens in Poland and in larger cities won't be much remarked on. In the countryside it will be more remarked on (though there won't be public shaming or shunning or anything like that).