As SmilingBluEyes mentioned, this is not a medical board and you really need to do some research about cytotec. Also, I'm not a nurse (as my name implies) but I am a labor doula with 8 years experience.
Please take this just as information from someone who, repeat, is not a nurse but who has worked with many, many moms in the past several years.
I, personally, am not a big fan of cytotec. I've heard of problems with uterine rupture with cytotec as opposed to other medications. As Mandana mentioned, cytotec is being used in labor and delivery off-label, meaning, it is not specifically approved for ripening cervices. It was originally meant to be a drug for the treatment of ulcers, I believe. They discovered (unfortunately for some women) that it would cause the cervix to ripen and it lead to a few miscarriages. It is FDA approved for ulcers, but it's not specifically approved for ripening cervices.
Cytotec is introduced to the cervix via a string, sort of like a tampon. Once you have it in place, you can't get out of bed for a while (8 hours, I believe? Someone please correct me if I'm wrong). Also, once they start using cytotec, it can't be stopped or controlled.
I'm a bigger fan of Cervidil, which accomplished the same thing yet doesn't have the same problems of cytotec. Cervidil is a gel that is placed on the cervix. You can't get out of bed with Cervidil either, but if you start having problems, it can be controlled better.
I've seen LOTS of good results from Cervidil. It would be great if your cervix would ripen on it's own but it sounds like your doctor has some concerns about your baby's size and your cervix may or may not ripen by 38 weeks, especially with a second baby.
This is just anedoctal information. Please, I do encourage you to do some research on cytotec as well as Cervidil. Ask your doctor, most importantly, and have an open dialogue/communication with him. This is most important. If you have any concerns, please be sure to let your doctor know.