To glance at realism, if the Blob is playing havoc on everyone’s genetics then it seems like there are two options.
If it isn’t messing with sex cells and it’s acting like a carcinogen where it mutates somatic cells then children should be normal, excepting some small outlier scenarios, and the mutations shouldn’t affect them at all.
If it is affecting sex cells in it’s editing of the victim’s genetics then it’s EXTREMELY unlikely that a fetus would develop and live- assuming the Blob isn’t also playing a role in that as well. The way development works is that for the majority of genetic flubs it will produce an unviable fetus and if it doesn’t die in the womb will likely be naturally aborted or stillborn. This can occur during a large portion of a pregnancy. Genetic birth defects exist on a very thin margin compared to the large amount of fundamental DNA required to survive and DNA that is functionally vestigial and not read.
A large portion of birth defects occur as a result of exposure to certain agents during a specific growth period for the fetus. Examples of this are Thalidomide exposure and Fetal Alcohol Syndrome. Unless the Blob is actively doing this it’s likely the baby would be healthy and normal… That said the survivor is prone to doing meth, drinking sewage, injecting artisanal mutagens, walking into radioactive craters, exposing themselves to portal storms, hobby bomb making, and probably gets a fair amount of exposure to lead and asbestos with as much basement diving and construction as they perform. So mileage may vary as far as a healthy baby after all that.
Source: Work in medicine and study neuroscience.
As an aside, this could be a questline- A refugee in the center finding out that- despite being pregnant- the baby is born either healthy or stillborn. Discussing this with the Doctor NPC could yield more info on this after quests like the blood sample or possibly bringing them information from a lab. Hell, maybe the Blob sterilizes humans as it simply doesn’t recognize sexual reproduction as a form of reproduction and just a resource waste. I mean the labs probably have info on this somewhere. I fully doubt injecting a pregnant woman with mutagen was too morally low considering some of the wild shit you see in labs.