I got the lapband in order to become pregnant, but using donor eggs/embryos, not my own, as I have diminished ovarian reserve. In order to minimize complications during pregnancy caused by being morbidly obese, both my RE and OB suggested lapband.
So far, I've lost 75 pounds. The thing is, I'm still 39 years old. I still have DOR. The chances of me becoming pregnant, accidentally, are slim to none. Buy my not becoming pregnant has nothing to do with my weight.
And, BTW, my periods have been regular, like clockwork, even at my highest weight. My REs (I've had two) were in shock that my periods were regular, but alas, they are.
As far as not feeling a pregnancy, if your placenta is attached to the front of the uterus, it is quite possible you would never feel a kick. And if you have always had a big belly, depending on how much weight you need to lose, that belly may take a while to shrink, and if you got pregnant and had the forward facing placenta, you may not know, especially if you never got a period (because the first time you finally ovulated you had perfectly timed sex and voila! your egg fertilized and implanted).
While I didn't watch the particular episode the original poster is referring to, it is quite possible the surgeon did mention the use of birth control but his patient either didn't hear him (how many of us have so many questions running through our heads that we sometimes miss what the surgeon is saying) or she refuses to acknowledge that he did tell her, thus not taking responsibility for her situation.
Regardless, I really don't see how a female patient in her child bearing years, who has done any amount of research into WLS, cannot NOT know that her fertility may increase as she loses weight.