[DrN]

Thanks Chris for that, but does that mean no immunity is passed from mother to baby during gestation? and also, no pathogens? If this is the case why is it so dangerous for pregnant women to catch viruses, such as rubella for instance?

The pathogens present will presumably be transferred from mother to baby at the same time as the mothers antibodies against them, if as you say the point is to transfer immunity, so the only real problem with this are those nasty bugs that our immune systems can't win the battle over (e.g. HIV)

but I assume my main point remains intact? that pathogens in the milk are more likely to result in disease when drank by the same species as the one which produced it?

[chris]

It all comes down to whether an infectious agent can cross the placenta. Some viruses which have no viraemic (blood-bourne) phase are safe - like herpes simplex, the cause of cold sores. But its relative, Chicken Pox, which intially replicates in the lungs and then establishes a viraemia (circulation and distribution of the virus in the bloodstream) can cross the placenta and infect the foetus. If this occurs early in pregnancy (first 20 weeks), when the major systems are being formed, it can have serious consequences. THe overall risk, however, is still quite low with only 1-2% of pregnancies affected.

But some viruses that are viraemic are still unable to cross the placenta. HIV, Hepatitis B, and Hepatitis C are all examples of this. Their inability to cross the placenta efficiently probably relates to the absence of a suitable receptor on the viral surface for placental cell antigens. It takes something else - like a doctor coming along with an amniocentesis or CVS (chorionic villus sample) needle to get the virus in.

Babies born to Hep B positive mothers are managed according to their mother's Hep B status which is known in the UK these days because Hep B assessments form part of the antenatal screen. Babies born to mothers with high-level infectivity receive anti-hepB antibodies at birth, followed by an accelerated course of vaccine. Babies born to low-infectivity carriers receive vaccination alone. It's important to prevent neonatal acquisition of Hep B since 80% of individuals under the age of about 3 years will go on to develop lifelong chronic hepB. Infection in adults, on the other hand, leads to lifelong infection only 15-20% of the time.

Chris

"I never forget a face, but in your case I'll make an exception"
 - Groucho Marx

[Monox D. I-Fly]

Then like how super stars sell urine to crazy people;

Wait, who?