Here's what Fauci has to say about sexual transmission:
A December 2019 letter from seven U.S. Senators to Dr. Fauci posed the question “What research is the agency planning to conduct or incentivize to improve understanding of modes of transmission, including vertical transmission.”
Dr. Fauci responded:
“Further exploration into non-vectored transmission of B. burgdorferi, such as sexual or vertical transmission, is needed to conclusively identify these routes as contributing to Lyme disease burden. However, adverse birth outcomes among women with untreated and disseminated Lyme disease during pregnancy have been shown.”
Here is a link to Fauci's letter.
(Thanks to Bruce Fries for sharing this information.)