The Avengers would likely have mixed reactions. Captain America might be very protective, seeing it as his duty to safeguard Black Widow and her unborn child. Tony Stark, on the other hand, might initially be more concerned about how this would affect their battle strategies.
Well, if Black Widow was pregnant during Infinity War in a fanfiction, it could greatly change her priorities. She might be more hesitant to engage in dangerous missions, as she has a new life to protect. This could lead to interesting conflicts with the other Avengers, who might not fully understand her newfound caution.
Black Panther was not featured in the original Infinity War comic. The comic focused on other characters and storylines. However, the movie expanded the scope and included him for a more diverse and engaging narrative.