My wife quit smoking when she found out she was pregnant and at her next doctor visit the doctor didn't like something he was seeing or hearing (can't remember the details but think it may have been blood pressure related) but asked her if anything major had changed recently! She said I quit smoking! He said start smoking again but just cut down as it is causing too much stress on your system and the baby! That's not the 1st time I had heard that!
I found out I was Preg in my second trimester...I was smoking Marlboro red 100's. I asked my ob about it.....as I was afraid I may have done some damage. He advised me to try and cut back, but don't quit especially cold turkey. Think about it...that baby has already been exposed to nic...you quit cold turkey, that baby goes through withdrawal too....and my ob said that my stress of cold turkey quitting would be more dangerous. I went from full flavor to B&H Deluxe ultra lights. I personally had not problems.
Everyone is different though and soooo many factors influence the way a pregnancy will go. For example...My mom did not smoke while preg with me....I have GOD AWFUL Sinus issues all year long. She did smoke with my brother as I was difficult enough at 9lbs 8oz and she was kinda hoping for a smaller baby (as they said that smoking will decrease the size of the baby)...well, he has NO problems with sinus issues and actually is sick (colds and such) a whole lot less than I am. He was born at 9lbs 8 oz as well.....
I am not saying to smoke or not smoke, but I see no problem with vaping to curb the stress of quitting analogs....stress can really cause a lot of problems during a pregnancy. One of the biggest problems with smoking while preg is the CO (carbon monoxide) that is inhaled via the combustion (real smoke). It takes the place of oxygen on the blood cells that are vital at feeding the fetus. When CO attaches, there is no place for oxygen and therefore it deprives the fetus of some of that very necessary oxygen.