Lamictal has never caused full-blown mania for me, but it has made me a little hypo-manic in the past, especially the first few days after increasing the dosage. However, for me, it doesn't cause increased cycling because it takes care of the depression side of things, for the most part. In higher doses, it does agitate me, so that's also something to be aware of.. Weird feeling; you're all doped up and agitated at the same time...
But, it has been known to happen; I know that it has caused people to cycle into higher levels of mania.
When I was put on Lamictal, my pdoc warned me that the med's slight anti-depressant effect could potentially set off mania, and that I should keep some of my Lithium on hand just in case this were to happen. But you should definitely speak with your prescribing doctor! Good luck!
Actually I eventually had to be transferred off Lamictal for that very reason although it was quite effective for close to 10 years.. From what my psychopharmcologist said (this could be verified by going to the medication website) "Lamictal can worsen mania at higher levels". That doesn't sound like that is what the cause is from what you are describing as it also has to be at a therapeutic dose to work. And during pregnancy any aspect of bipolar can worsen. This is complex but definitely speak to your psychiatrist about it and definitely keep track of whether mania or anything other aspects of bipolar the Lamictal is treating improved, worsened or remained the same as the dosage is increased.
lamictal never causes mania. BUT it doesn't help in mania. this is a fact
I don't have experience with Lamictal but why don't you put a call into your Physc-doctor. If it were causing me mania it may not be the drug for you, especially being pregnant.