She needs to get to Dr. Jones in CT immediately. Your brother is right to bug out. While there have been woman with lyme who have not been treated and didn't know they even had it and had children that were fine.
Then there are woman like a friend of mine who got bitten in her first trimester and lost her baby in her second trimester because she didn't know the story about lyme and only got two weeks of antibiotics when she first got bitten.
Dr. Jones has treated the most pregnant woman with lyme of any physician in the world.
There are certain antibiotics which are safe during pregnancy. Please get her to Dr. Jones or an LLMD ASAP.
I had Lyme disease while 20 weeks pregnant 6 years ago. It was treated immediately (once symptoms of rash, fever, flu appeared) approx 2 weeks after the bite. I worried a lot about it at the time and everything turned out to be fine. I have a beautiful healthy 6 year old girl.
Since I am allergic to the Penicillins and can't take Tetracycline when Pregnant, I took Erithromycin for 4 weeks and it did the trick for me.
I also consulted an infectious disease doctor at the time to confirm the best treatment method since I was pregnant.
It is good of you to find out information for your brother and his girlfriend. Does she have a Lyme rash? If so, get photos of it. Place something near it, like a coin or ruler, before photographing it to give it size definition. This way you have documentation of it.
Lyme disease can be passed through pregnancy and breastfeeding. It is important for her to be treated throughout the pregnancy to minimize the possibility of transmission. Where does she live? As was stated, Dr. Charles Ray Jones in New Haven, CT is the best Lyme pediatrician in the country, and he has a lot of experience with Lyme and pregnancy. Please have your brother's girlfriend call him for advice.
Besides Lyme, ticks can transmit several co-infections including Babesiosis, Ehrlichiosis (HME & HGE), Bartonella, and Mycoplasma. Many people who have Lyme are co-infected. It is important to be tested by a Lyme lab such as IgeneX in Palo Alto, CA.
She may also want to contact the Lyme Disease Foundation. Its founder had a personal experience with Lyme and pregnancy.
Please let us know how she is doing okay? They are lucky to have you helping them.
Do you have any kind of symptoms? It is my understanding that four weeks of treatment is not long enough for Lyme. If you do have any symptoms, you may want to be evaluated by a Lyme knowledgeable doctor.