I don't know it that true, but my sex drive is extremely low. I didn't have sex my from my first trimester with my second due to my babies father being in jail. I certainlu wasn't going to have sex with anyone else. But she was the easiest labor I had.
Sex makes labor easier for you in the long run... and towards the end the semen can help ripen the cervix because of the prostaglandins released... orgasms make uour uterus contract... its not necessary, but it makes an easier experience... my first I had sex up until the day I went into labor... I was 38 weeks... I was dilated at 35 weeks and by my 37 week appt 2cm and 80% effaced... I never made it to my 38 week appt since I was in the hospital in labor... there are times throughout your pregnancy where you will want it more than other times... its all normal
We'll later in pregnancy it's good for helping to soften the cervix. Some say it helps bring on labor. I think it's great anytime during pregnancy if for nothing else but the exercise lol