Altered umbilical cord blood complement profiles in preeclampsia and preterm birth pregnancies

To ensure a successful pregnancy, a delicate immunological balance is essential at the feto-maternal interface. Dysregulation of the complement system is linked to adverse pregnancy outcomes such as fetal growth restriction, preeclampsia and preterm birth. However, it is unknown how this translates into umbilical cord concentrations of complement factors.

Umbilical cord blood samples were collected from 12 term vaginal births, 12 term elective caesarean sections, 11 preterm births, and 14 cases of preeclampsia. C1q, C4, C3, MBL, Factor H and properdin concentrations were measured.

In term pregnancies, MBL, factor H and properdin concentrations were significantly lower in elective caesarean sections compared to vaginal deliveries. In preeclampsia, umbilical cord blood showed lower concentrations of C1q and MBL and a higher concentration of properdin compared to term deliveries (n = 24). Within the preeclampsia group, C1q, factor H and properdin correlated to gestational age. Early onset preeclampsia showed significantly lower concentrations of C1q, factor H and properdin compared to late onset preeclampsia. Preterm births compared to term births had significantly lower concentrations of C1q, C4, C3 and MBL.

Concentrations of C1q, C4, C3, and MBL in umbilical cord blood are lower in cases of preeclampsia and preterm births compared to term pregnancies. The complement system in fetuses seems to develop throughout gestation, approaching concentrations at term that are similar with established reference values in adults. Higher concentrations of lectin and alternative pathway components in term births versus term elective caesarean sections likely highlight the inflammatory process associated with labour.