I decided not to last year for several reasons (much to my mfm's annoyance but my ob never said a peep about it). One, they change it every year and never test it in pregnant women, which made me very uncomfortable. Two, I read a Cochrane Review article questioning the safety and effectiveness of the flu shot (I can't find the same one that was from last year, but here's a link to an older one with similar information http://www.medicalnewstoday.com/releases/55507.php
). Three, I wasn't working( (but also did not get it/was not going to get it in my first pregnancy when I was teaching middle schoolers, and that was with the H1N1 hysteria in full swing). And I was not due near flu season- April/May (but also was not going to get it when I was due in January.) If you do get it, make sure you get the thimersol free version. Definitely don't get it in the first trimester. But besides that, if you are going to get it, you can pretty much get it whenever.
As for the Dtap/Tdap (whooping cough), they usually like you to get it before pregnancy, but if you haven't had it in the last 2 years, they will usually give it to you in the hospital. I made DH get it before the baby was born and also made my parents get it. (Well, I didn't really "make" them get it, but I told them if they didn't, they weren't going to be holding my newborn.)
I'm not really a big vax fan, we are vaxing Lucas on a delayed schedule (only 2 shots at a time per visit/month instead of the 6 or so they are supposed to get, and some vax that are not necessary for newborns, like the Hep.B they give them at birth, we are delaying indefinitely as I am certain that I do not have Hep.B -they test you in your prenatal bloodwork- and I'm certain my newborn/infant is not sharing needles or getting a tattoo or at risk to contract Hep.B. They give it at birth to "catch" the babies from mom's with Hep.B that do not know it, but for many babies, the Hep.B is not necessary until much later.)