How to explain that microbes from maternal origin may be pathogenic for the baby?
Several decades ago, we learned that, compared with the placenta of other mammals, the human placenta is highly effective at transferring Immunoglobulin G (IgG) to the fetus (Cederqvist, Ewool and Litwin 1978). Since that time, we have assumed that, immediately after birth, the baby’s body urgently needs to be colonized by microbes familiar to the mother. If these familiar microbes are the first to occupy the territory, they are protective. Furthermore, they start programming the immune system of the baby. In general, one of our causes for worry in the perinatal period is the negative effect of a specific microbial deprivation, particularly when babies are born in a bacteriologically unfamiliar place and/or have been exposed to antibiotics and/or are not born through the bacteriologically rich perineal route.
In fact, interpretations are offered by studies that modulate the general rule of an easy placental transfer of antibodies, particularly intense from 38 weeks onwards. One must take into account that there are four subclasses of IgG and that the transfer of the subclass 2 (related to GBS) is not as effective as the transfer of the other subclasses (Garty et al. 1994, Hashira, Okitsu-Negishi and Yoshino 2000). This is a way to interpret the apparently mysterious vulnerability of human babies – particularly premature babies – to streptococci B transmitted by the mother.”
– Michel Odent
Odent M (2015). Group B Streptococcal Infection: beyond the mysteries. Midwifery Today 113: 12-13.