Can e.Coli cause severe birth defects?

Not generally. Ecoli is a bacteria generally found in the intestinal tract, it can cause many different types of infections, most commonly urinary tract infections. Any serious infection can increase the can of premature delivery, which can cause developmental delay, but this is generally avoided with prompt treatment.
Potentially. If it causes pyelonephritis, cystitis or even asymptomatic bacteriuria, e. Coli can lead to preterm birth with all its complications. If it causes severe fever, it can be a teratogen via the excess heat to the fetal neurocord and heart primarily (pyelonephritis, febrile gastroenteritis, ehec, etec). If it causes dehydration it can trigger miscarriage of preterm birth. In short, avoid it!