Untreated Lyme disease during pregnancy can lead to infection of the placenta, states the CDC. Spread from mother to fetus is possible but rare. https://www.cdc.gov/lyme/transmission/index.html  Note that not all fetus's infected gestationally with borrelia parish.  A lot survive to live challenging lives sick left to be cared for debilitated and sick parents.
It has been shown that an infected mother can transmit the infections to the fetus which can cause many difficulties during childhood that often persist throughout the child’s life. Symptoms in children can be devastating to the health and well-being of the children and their families. Often mothers experience seemingly unrelated physical and psychiatric symptoms that are diagnosed as Lyme when their child is diagnosed.