Thanks for posting. I'm happy to hear you're getting into powerlifting, it's so much fun and you're going to love it! I have been an athlete my whole life as well and I really wanted to get back into a competitive sport so powerlifting was a perfect option for me.
Funny you ask about prenatal vitamins, I took them throughout my pregnancies and I still take them now (not planning on another baby but I like my prenatal vitamins) my hair, nails and skin are so much better when I use them regularly.
I took supplements while I was pregnant as well, no stimulants for obvious reasons but I continued to use Flameout for my omegas and Metabolic Drive for a protein source. Most supplements will give you a warning on the back about pregnant or breast feeding women but you can double check with your doctor or midwife (when you are pregnant) and see what they recommend. The thing about pregnancy is EVERYONE has their own opinions about what you should and shouldn't do... Just like training, everyone has their own theories and systems that they think are the best. I went with how my body felt and if I had any concerns my midwife was just a phone call away!
I trained while I was pregnant with both boys up until 7.5months, I reduced the weight and restricted my exercises as the pregnancy progressed... This is when you really need to listen to your body! I continued to stay active up until the day of the births, I was outside going for walks everyday and even while I was in labor I was walking most of the time because it felt more comfortable for me (I didn't have an epidural with my 2nd so I was mobile the whole time)
I would say starting the prenatal vitamin now is a good idea, you can also start to take folic acid when you start "trying" to get pregnant. And for now.... Train your ass off because if you're anything like me you are going to miss heavy lifting during the pregnancy!!
If you've got any more questions at all, feel free to ask. My boys are 1 and 3(almost) so I remember it like it was yesterday