Background: Hydroxychloroquine (HCQ) has been used in the treatment of systematic lupus erythematosus (SLE) and antiphospholipid syndrome (APS), but its effect on lupus activity during pregnancy, preeclampsia and intrauterine growth restriction (IUGR) remains unclear. Methods: PubMed, Embase and Cochrane databases were searched before 11 September 2022 for randomized clinical trials (RCT) or observational studies involving additional HCQ treatment and pregnant women diagnosed as having SLE and/or APS/positive antiphospholipid antibodies (aPLs). Risks of high lupus activity, preeclampsia and IUGR were explored. Results: One RCT and 13 cohort studies were included. A total of 1764 pregnancies were included in the pooled meta-analysis (709 in the HCQ group vs. 1055 in the control group). After the additional use of HCQ, the risk of high lupus activity decreased (RR: 0.74, 95% CI: 0.57–0.97, p = 0.03). For preeclampsia, the total incidence decreased (RR: 0.54, 95% CI: 0.37–0.78, p = 0.001). The subgroup analysis showed statistical significance in the SLE subgroup (RR: 0.51, 95% CI: 0.34–0.78, p = 0.002) but not in the APS/aPLs subgroup (RR: 0.66, 95% CI: 0.29–1.54, p = 0.34). For IUGR, the decrease in incidence was not statistically significant (RR: 0.80, 95% CI: 0.47–1.35, p = 0.46), neither in the SLE subgroup (RR: 0.74, 95% CI: 0.40–1.36, p = 0.33) nor in the APS/aPLs subgroup (RR: 1.26, 95% CI: 0.34–4.61, p = 0.73). Conclusion: The additional use of HCQ may decrease the risk of high lupus activity during pregnancy and the incidence of preeclampsia for SLE patients, but the results do not support that using HCQ decreases the incidence of preeclampsia for APS/aPLs patients or reduces IUGR risk for SLE and/or APS/aPLs patients.

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