Iron is key during pregnancy... Low iron can lead to fatigue during pregnancy, depression, more bleeding post delivery as well as a longer recovery time. Iron found in vegetables comes with vitamin c in the plant so is easily absorbed and the iron level per calorie is higher in plant forms than meat. Dark green leafy vegetables, dates, raisins are all good sources of iron
Also maca root powder helps fertility levels. You will find it in the health shop. Boost your vitamin E also (avocados)
I've been veggie/ mostly vegan for over 22 years. ^^b12 was a requirement for vegan diets because it's only found in animal products including dairy and eggs which many vegetarians eat. Vegan foods (the milk and dairy alternatives) are generally fortified with b12 so it's not an issue these days as it used to be.
Regarding conceiving, I strongly recommend you stay vegetarian and possibly cut out dairy during this time. Most animal products have vast amounts of hormones in them that are pumped into the animals. These can interfere with our own hormones if we are very sensitive. My sister had problems conceiving and both she and her husband cut out animal products, caffeine, alcohol and conceived within 6 months. They have 2 kids now - 10 and 8 years old :)
And take vitamine B12. Its common for vegetarians to have a B12 deficiency because its excpecially found in meat. B12 is important for the developping brain.
Yes I have been a vegetarian for 10 years and just gave birth to my first child 4 months ago. I don't think being a vegetarian would effect conception or pregnancy at all, just make sure you consume enough protein, calcium and iron in addition to your prenatal vitamins.