This is a question I got from an audience member post-FreeOK, and it was too good not to share with everybody!!
First, a disclaimer I dont normally have to state– I iz not an MD, I am an almost PhD. Talking about the general science of antibodies/mommies/babbies, not giving medical advice, here.
First, the good news:
Fetuses (fetii?) and babbies are protected from pathogens, even though their own immune systems have not matured yet. How do they manage this feat? They steal antibodies from Mommy!
Remember yesterday I said the same antibody can have lots of different butt-ends? The same ‘business end’ that recognizes tetanus toxin or a variant of influenza, but different back-ends– each different butt has a different skill set.
One of IgG antibodies special powers is that they have the ability to cross the placenta! This means that if Mom gets infected with something nasty, and something nasty gets into Fetus, the antibodies can go over and help Fetus out, even though other parts of Moms immune system are ‘trapped’ on Moms side of the placenta. Having Fetus away from Moms immune system is otherwise a Good Thing (Fetus obviously isnt ‘self’. Moms immune system would kill it). Letting IgGs cross the placenta to help Fetus a bit is normally a Good Thing, but sometimes the process backfires– If Mom and Fetus have a different blood-type, sometimes Moms IgG antibodies blow up Fetuss red blood cells, and Fetus can die…
But we have drugs to fix that, if there is any risk of that kind of immunity developing, or evidence it has developed!
That takes care of Fetus– But Newborn Babbies steal Moms antibodies a different way! IgM and IgA antibodies have a superpower that lets them be secreted— in tears, in saliva, in mucus, and in breast milk! As long as Babby is breastfeeding, it gets all of Mommys secreted antibodies! Yay!
So, if Mom has been properly vaccinated, she has antibodies to measles, mumps, chicken pox, etc etc etc, and those are transmitted to Babby and protect it, if Babby is directly exposed to a pathogen. If Mom is exposed, her antibodies probably keep the pathogen from replicating/establishing infection at all, so Fetus and Babby are safe if their contact is indirect too.
SO! My ‘Im not that kind of doctor’ advice to future Moms would be to make sure all your vaccines are up to date before you get pregnant.
Cause we all know pregnancies are carefully planned.
On that note… now for the bad news…
As Ive written about before, just by chance, not everyone who gets a vaccine gets a protective antibody response. Sometimes the vaccine stimulates the proper immune response, but your body doesnt come up with a very good ‘answer’. Sometimes it comes up with a perfectly good answer, but promptly forgets it ever saw the pathogen. And sometimes, because vaccines are crippled/dead/fragments of pathogens, your body just ignores them until they degrade and go away.
So some of us are not protected against, say, measles, at all, even though our parents were responsible and made sure we got our MMRs– but we dont know it because we are surrounded by people who are protected, thus we are protected by herd immunity. There is no way of knowing this until you are exposed to a sick person and get sick yourself (well, you could try to convince your MD to do antibody titer tests on major pathogens, maybe?).
IF Pregnant Mom does not have protective immunity against rubella, and she gets exposed to an unvaccinated child infected with rubella, rubella will be able to cross the placenta and kill Fetus.
Another example of trouble– Mom might be exposed to a kid with whooping cough. Mom had whooping cough a long time ago, so it takes her immune system a bit to remember how to fight it off again. In the meantime, she might get a teeny, tiny cough, not thinking twice about it… transmitting to Babby before her own antibodies pop up to protect Babby in breast milk. And, Babby has no B-cells to ‘remember’ whooping cough on its own, so Babby gets really sick.
Even if Mom is totally immunized and responded beautifully to every shot, Newborn Babby can still be at risk of becoming sick when they stop breast feeding. Mom might get coughed on by an unvaccinated kid with measles. Spit droplets embed in Moms shirt. Mom goes home to cuddle Babby… Babby can get sick. HIV-1 might be a wuss outside the body, but other viruses are sturdier and can play indirect tricks like that.
Evolution and modern medicine have come up with lots of ways to protect a mom and her fetus/babby from pathogens.
Anti-vaxers can undermine everything, even if YOU do everything right.