Normal pregnancy is characterized by systemic activation of the complement system.

Area of Science:

• Immunology
• Reproductive Biology

Background:

• The complement system, a key part of innate immunity, is linked to pregnancy complications like fetal loss and placental inflammation in antiphospholipid antibody syndrome.
• While complement inhibition is proposed as essential for normal pregnancy, pregnancy itself involves generalized innate immune activation.
• This study investigates if normal pregnancy is associated with complement activation in the maternal circulation.

Purpose of the Study:

• To determine if normal pregnancy is associated with complement activation in the maternal circulation.
• To quantify anaphylatoxin levels (C3a, C4a, C5a) in pregnant versus non-pregnant women.

Main Methods:

• Plasma samples from 134 normal pregnant women (20-42 weeks gestation) and 40 non-pregnant women were analyzed.
• Specific immunoassays were used to measure concentrations of anaphylatoxins (C3a, C4a, C5a).
• Non-parametric statistical methods were employed for data analysis.

Main Results:

• Median plasma concentrations of C3a, C4a, and C5a were significantly elevated in pregnant women compared to non-pregnant women (p<0.001).
• Anaphylatoxin levels did not vary significantly with advancing gestational age (p>0.05).
• Positive correlations were observed between C3a and C4a (r=0.36, p<0.001) and between C3a and C5a (r=0.35, p<0.001).

Conclusions:

• Normal human pregnancy is characterized by evidence of complement activation, indicated by higher circulating levels of anaphylatoxins C3a, C4a, and C5a.
• Physiological complement activation during pregnancy may serve as a compensatory mechanism to protect the mother against infection.