Antiphospholipid antibodies (aPL) can induce fetal loss in experimental animal models. Human studies did find hypocomplementemia associated to pregnancy complications in patients with Antiphospholipid Syndrome (APS), but these results are not unanimously confirmed. We have then performed a multicenter study to identify if preconception decreased C3 and/or C4 levels could be considered a risk factor for adverse pregnancy outcome (APO) in APS and aPL carriers pregnancies.
We performed a multicenter study including 503 pregnancies from 11 Italian and 1 Russian Centers. Data in women with APS and asymptomatic carriers with persistently positive aPL and preconception complement levels were available for 260 pregnancies.
93 (36%) of all pregnancies had low levels of preconception C3 (51, 55, %) or C4 (13, 14%) or both (29, 31%). 167 (64%) pregnancies had normal complement levels. In pregnancies with low preconception C3/C4, a significantly higher prevalence of pregnancy losses was observed (p=0.008). A subgroup analysis focusing on triple aPL positive patients found out that preconception low C3 and/or C4 levels was associated with an increased rate of pregnancy loss (p=0.05) as shown in Table 1.
Our findings confirm that decreased complement levels before pregnancy are associated with increased risk of APO. Pregnancy losses has been seen only in women with triple aPL positivity, indeed single or double positivity does not show this trend. Complement levels are cheap and easy to be measured therefore they could represent a useful aid to identify patients at increased risk of pregnancy loss.