Objective To describe pregnancy outcomes in patients with SLE treated with belimumab before and/or during pregnancy.

Methods Data of prospectively-followed pregnancies (2014–2022) in 7 Italian centers were retrospectively collected.

Results Twenty-four SLE pregnancies were included (median age at conception: 33 [21–37] years; 15 primigravidae).

Belimumab was stopped in 4 cases preconceptionally, in 10 at positive pregnancy test and in 10 during pregnancy (4 during the 1^st trimester, 3 during the 2^nd trimester and 3 during the 3^rd trimester). The timing of discontinuation was planned with the patient during preconception counselling.

Other medications included prednisone (92%); antimalarials (83%); azathioprine (46%); calcineurin-inhibitors (25%); low-dose aspirin (88%); heparin (58%).

At preconception, median SLEDAI was 4(2–4).

One patient who discontinued belimumab at the 11^th week had active nephritis from preconception.

Three flares (cutaneous; pericarditis; hematologic) occurred during the 3^rd trimester in the group of patients who discontinued belimumab at positive pregnancy test, while 1 flare (cutaneous + articular) occurred in the 1^st trimester in the group of patients who continued belimumab.

Live-birth rate was 87.5%. Two miscarriages and 1 intrauterine fetal death (37^th week; fetus with 21-trisomy and atrio-ventricular defect) occurred. One perinatal death occurred (patient with thrombotic+obstetric APS and lupus nephritis who underwent heterologous assisted reproductive technology -embryodonation- and developed eclampsia with cerebral haemorrage at 25^th week; an urgent cesarean section was performed; the newborn died after 3 days).

Two cases of pre-eclampsia in patients with multiple risk factors were observed.

Five newborns were hospitalized in Intensive Care Unit for: milk protein intolerance; desaturation; respiratory distress; prematurity (2 cases). One sepsis starting from urinary tract infection occurred in a 2-months-old infant with calico-pyelic and ureteral dilatation at birth. One newborn presented with interatrial defect and situs inversus (paternal 10 chromosome inversion).

Conclusions Despite our data do not allow definitive conclusions, the live birth rate and the exclusion of drug-related congenital defects are encouraging. SLE flares occurred more frequently after Belimumab discontinuation at positive pregnancy test. We suggest that women on good disease control while on belimumab could be offered to continue it and to discuss discontinuation timing according to their specific risk/benefit ratio.

Acknowledgements ‘Gender Medicine’ Study Group of the Italian Society for Rheumatology