Yes, it is possible to accidentally get pregnant at 42, although the chances are significantly lower compared to younger women.
According to research, pregnancy rates decline as women age, especially after 40. "Approximately 15% of pregnancies occur in women over 35," and "after 40, it's even less common, with a rate of less than 3%," although that's increasing as more women delay marriage and kids, have second marriages and, of course, undergo fertility treatment.
Therefore, while less likely, pregnancy at 42 is still a possibility if precautions are not taken.
