I'm so sorry that I have to be the one to say that to you, but the truth is that no one knows when or why it gets passed to some and not other babies during pregnancy, as with most things that have to do with these diseases, more studies need to be done.
The thing that you have to be sure of is where you are getting your information. We are in the middle of a huge 'war'. The two sides are the IDSA (Infectious Disease Society of America) & ID doctors and ILADS (International Lyme and Associated Diseases Society) and their doctors. Unfortunately we are all caught in the middle of this "war" - it affects every aspect of this disease - getting diagnosed, finding information, getting treatment that actually works. If you aren't aware of this controversy, here are a couple of links that I believe explain it pretty well:
www.clinicaladvisor.com/controversy-continues-to-fuel-the-lyme-war/article/117160/#www.ncbi.nlm.nih.gov/pubmed/20946067 Here are a few of the many links that can lead you to the info about
Lyme being passed during pregnancy:
www.drjoneskids.com/ I can't get a link to send you directly to the info, so if you will scroll down until you see the link that says "Pregnancy and Lyme" on the left side of the page.
The ones that have the most information are the links at the bottom of the article that say "Pregnancy outcomes" by John Drulle and Lyme & pregnancy - in my opinion. The others just say that more research is needed, even though they document very real issues.
The other thing I would suggest is that you search the internet using the terms "congenital Lyme" and do some more reading. Even if the chances aren't very high for this to be passed, telling Moms and Dads that it can't happen is very wrong!
There are other tick-borne infections that have enough evidence of being passed to the baby during pregnancy that you should really be aware of them as well as for yourself - Lyme usually isn't the only disease passed when a tick attaches. Bartonella and Babesia are the most common, I believe, but they are by far the ones that have the most research into them other than Lyme.
On Dr. Jones Kids site that I referred to above, there are also links for Bartonella being passed during pregnancy.
Here is another one:
news.ncsu.edu/releases/bartonella/ The other one that I know of that can be passed in utero is Babesia - even the CDC admits to that one!
www.cdc.gov/parasites/babesiosis/gen_info/faqs.html Again, I'm so sorry that you had to find this info out on a forum, but I always feel the need to explain that there is a very real possibility that it can happen.
We have several mothers of young children on here that are very helpful, I'm sure you will meet up with them soon! They have done a lot more investigation into these things that I have done - my kids are all grown up.