My questions: When does fetus begins to acquire antibodies from mother? Does it continue throughout the pregnancy?

From Wikipedia: http://en.wikipedia.org/wiki/Passive_immunity

This occurs around the third month of gestation.

From Helena Curtis Biology :

During the last month of pregnancy , the baby usually begins to acquire antibodies from its mother,....

I believe that both these sources are reliable but they contradict when the transfer of antibodies starts.

  • 1
    $\begingroup$ only IgG-1, 3 & 4 cross the placenta. The transfer of antibodies would start as soon as umbilical vein develops. $\endgroup$
    Oct 25, 2013 at 4:34
  • $\begingroup$ @WYSIWYG Yup, those are the antibodies that are transfered but I am interested in when they are transfered. $\endgroup$
    – biogirl
    Oct 25, 2013 at 4:37
  • $\begingroup$ as i recall, they are actually gathered by cells and actively transported across the placental barrier. there is an Fc receptor. a trained immunologist might be the best person to answer this question. $\endgroup$
    – shigeta
    Oct 25, 2013 at 12:55

1 Answer 1


Both are technically correct. Here's a review that goes into some detail about the process: IgG Placental Transfer in Healthy and Pathological Pregnancies. It's worth a read if you're interested in the subject. In particular, it cites a study of immunoglobulin transport which:

demonstrated a continuous rise in IgG levels in the fetal circulation between 17 and 41 weeks of gestation. Fetal IgG concentrations were only 5%–10% of the maternal levels at weeks 17–22 but reached 50% of the maternal concentrations at weeks 28–32. The majority of IgG is acquired by the fetus during the last 4 weeks of pregnancy, and fetal IgG concentrations usually exceed maternal ones by 20%–30% at full term.

So it begins a wee bit before week 17, so definitely within the second trimester, but it is only by the third that concentrations begin to be truly meaningful. However, most of the antibody acquired, going above the maternal level, is done in the last month.


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