Protective function
Strictly speaking, the placenta forms a "protective barrier" against infectious agents. Nevertheless, there are some microbes that can cross this barrier, occasionally following placental lesions.
Sexually transmitted diseases:
- After the 5th month of pregnancy treponema pallidum bacteria, the syphilis pathogen, can pass through the placental barrier. The infection of the fetus can lead to a miscarriage or leave behind congenital abnormalities.
- In industrialized countries, the HIV transmission from the mother to the fetus amounts to roughly 15 to 25%. It depends on the viremia status of the mother. There are a variety of transmission possibilities, but the transplacental infection with HIV during or shortly before birth appears to be the most frequent. Probably infection frequently also occurs during the passage of the child through the maternal birth canal (HIV in the cervix mucus).
The following precautionary measures can be taken:- Anti-HIV treatment during the pregnancy and birth as well as further treatment of the newborn during the first few weeks.
- Birth via caesarian section.
- No breastfeeding of the child
When all of these measures have been carried out the risk of infection for the baby can be reduced to below 1%.
- Gonorrhea (Neisseria gonorhoeae) arises through infection with gonococci. The child can be infected via vertical transmission (during birth) and develop an infection of the eyes (blennorrhoea neonatorum).
Fetotoxic infections:
In addition, the placenta also presents an incomplete barrier against certain injurious effects of drugs: Antibiotics and corticoids can pass through the placental barrier. Depending on their size, certain steroid hormones get through as well.
The same is true for certain medications the teratogenic effects of which are today well documented.
Thalidomide, mainly responsible for phocomelia (prescribed in the 60's), as well as Roaccutane (retinoic acid, commonly used for treating acne), are highly teratogenic.
The consumption of barbiturates, drugs and alcohol during pregnancy are also to be avoided!