For a long time acetaminophan, a class of drug termed a cycloogenase inhibiter, was considered to be "safe" for use during pregnancy. This view has recently been questioned. In the Journal Pharmacology Reports Dec 2012: 64(3) 521-7 they conclude that there is a prenatal risk to use of acetaminophan, the risks including asthma in childhood, pulmonary embolism, miscarriage, phlebothrombosis, pre-eclampsia and cryptochidism
Please consult with your OB/GYN Specialist before taking any medications while pregnant is my advice.
That is an excellent question and the answer is "probably no risk", but not 'absolutely positively". Remember that elevated temperature is part of the immune response. Certain organisms cannot replicate or survive except within a narrow range of temperatures. One of the reasons people take Tylenol is to reduce fever. The fact there is no data supporting problems with acetaminophen does not mean there is no element of risk.
Yes, acetaminophen is Tylenol which is one of the only recommended pain relievers to take during pregnancy. Just make sure to take the directed dosage and only take when needed.