TABLE 1.

Studies assessing the correlation of C3 and C4 serum levels with obstetric outcome in pregnant women with anti-phospholipid syndrome.

Author, year	Number of APS patients/pregnancies	Study design	Timing of C testing	Control group	Main findings
Ruffatti, 2011 (50)	114/114 All PAPS	Retrospective	Baseline and at the end of pregnancies	None	- Hypocomplementemia was associated with adverse pregnancy outcome at univariate analysis.
De Carolis, 2012 (51)	47/47 PAPS/SAPS (No SLE)	Prospective	Within 20 gestational weeks	None	- Hypocomplementemia was associated with fetal loss and preterm delivery at univariate analysis. - Women with hypocomplementemia had lower neonatal birth weight. - Hypocomplementemia was not associated with PE and IUGR at univariate analysis.
Reggia, 2012 (49)	45/57 PAPS	Retrospective	I-II-III trimester	49 women with UCTD/SjS 175 healthy pregnant women	- Hypocomplementemia was not associated with adverse pregnancy outcome in PAPS women. - Women with PAPS had lower C3 and C4 than healthy women, but similar to UCTD and SjS.
Deguchi, 2017 (52)	69/81 PAPS/SAPS (mainly SLE)	Retrospective	NS	None	- Hypocomplementemia was not associated with pregnancy loss, premature delivery and IUGR. - Hypocomplementemia was associated with hypertension at multivariate analysis.

PAPS, primary anti-phospholipid syndrome; SAPS, secondary anti-phospholipid syndrome; C, complement; NS, not specified; SLE, systemic lupus erythematosus; UCTD, undifferentiated connective tissue disease; SjS, Sjögren syndrome; PE, pre-eclampsia; and IUGR, intra-uterine growth restriction.