At how many weeks' gestation does the fetus primarily begin to produce IgM?

The production of IgM, which is the first antibody type to be produced by the fetus, begins primarily around the 10 to 15 weeks gestation period. At around this time, the fetal immune system starts to mature, and the hematopoietic tissues, especially the liver, become involved in the production of immunoglobulins, including IgM. This is significant because IgM is crucial for the initial immune response, playing a vital role in the fetus's ability to respond to infections.

Prior to week 10, the fetus does not have a fully functional immune system, and therefore, antibody production is minimal. After the 15-week mark, the production of IgM typically increases and marks the development of a more robust immune response, allowing the fetus to better defend against potential pathogens. Therefore, the timeframe of 10 to 15 weeks accurately reflects the onset of IgM synthesis in fetal development.