Legionella and pregnancy

I know that they said a pregnant woman’s fetus is safe from the bacteria, even if the woman ingests/breathes in infected water, however, what about from the point of conception until the placenta is in place? Are there any risk factors during this 2 week period of time? Could bacteria create any problems with getting pregnant? Thank you for taking my questions.


Infection during pregnancy is not a good event, in general, from a common sense viewpoint. And, pneumonia can have adverse effects for mother and child. However, only one case, to our knowledge, has been described in which pneumonia led to death of the fetus – this was a report by Italian investigators. In 2 cases of Legionnaires’ disease in pregnant mothers, antibiotic therapy was curative for the mothers, and the 2 babies that were subsequently delivered were healthy. So, fetal death due to Legionnaires’ disease is extremely rare. Some infections such as rubella (German measles), measles, cytomegalovirus infection, and bacterial meningitis are causally linked to fetal defects and adverse effects long-term for the child (e.g. deafness, mental retardation). This has not been the case for Legionnaires’ disease. Keep in mind that the highest avoidable risks for Legionnaires’ disease are those who smoke cigarettes. So, quitting smoking during pregnancy is good for both child and mother. In response to your last question, Legionnaires’ disease has not been linked to infertility.

Follow Up Question:

Thank you for your quick response. To clarify, the only way that it’s even a remote possibility of danger to the fetus (from conception forward) is if the mother actually comes down with the disease? If I’m ingesting or breathing in this bacteria and my body is healthy and therefore, successfully fights it off, there is no risk to the fetus?

Follow Up Answer:

Yes. No danger exists for the fetus if the mother is healthy. The risk to the fetus is probably not so much invasion by Legionella, but that the pneumonia causes respiratory compromise or shock to the mother. For reality purposes, I think that the risk for an unborn baby to be harmed is so close to zero that neither you nor any other healthy expectant mother should be concerned.

This confidence comes from:

  1. Experience – no one in the world has seen more cases of Legionnaires’ disease than we – and we have never encountered a case. On the other hand, we have encountered directly or indirectly cases of Legionnaires’ disease in infants, children and mothers in maternity hospitals. In these few cases, the infection was delivered directly to the infant or child by the water; however, the Legionella was not passed through the placenta to an unborn baby. We are also the authors of the first comprehensive report of Legionnaires’ disease in pediatrics and in 2006, we sounded the warning to infectious disease specialists and pediatricians to alert them that infants and children could contract Legionnaires’ disease ( Lancet Infectious Diseases, 2006). This article can be downloaded from the Publications section. I wouldn’t bother, however – it is for pediatricians and not for laypersons – you might freak out.
  2. Logic and extrapolation. We are authorities on hospital-acquired (or building-acquired) Legionnaires’ disease. Legionnaires’ disease has occurred in women’s hospitals and children’s hospitals from the drinking water. Despite this vast experience, we know of no cases of fetal harm in a healthy mother. (Nor would we ever expect such a case).


In short, rest assured that you and your baby are safe.