Final answer:
The round ligament is the most likely ligament to be affected if a pregnant woman is experiencing sudden sharp groin pain, as it can become stretched and cause pain during pregnancy.
Step-by-step explanation:
If a pregnant woman is experiencing sudden sharp groin pain, based upon the location of her symptoms, the ligament likely to be affected is the round ligament. This ligament attaches to the uterus near the uterine tubes and extends to the labia majora. During pregnancy, as the uterus expands, the round ligament can stretch and tense, which can cause sharp pains or spasms, often referred to as round ligament pain. This is a common type of discomfort during pregnancy.