This is the inguinal region where the round ligament is crossing. It is a completely harmless pain, but is can really knock a woman for a loop and stop her dead in her tracks. Usually, changing position will relieve this strain on the ligament, lessening the discomfort, but the only final cure is delivery several months later. The second trimester is the first time real expansion begins. Stretch marks begin, sometimes invisibly.
Moles get bigger, skin tags get bigger, even warts can get bigger.
Thanks to estrogen, everything has a better blood supply. This also explains why gums may bleed after tooth brushing. This is also the most stable time for the pregnancy, too. The second trimester gives a pregnant woman a break, for the first and third trimesters provide much more intense worries. And if the big, bad things are ruled out, this time can afford a woman the opportunity to rejoin the world after the initial frights of the first 12 weeks.