Birth weight
We examined both small for gestational age (SGA) and low birth weight (LBW) because reports on biologics use during pregnancy and neonatal birth weight varied. LBW was defined as less than 2.5kg at birth regardless of gestation while SGA was defined as <10th centile for weight at birth by gestation. In the LBW group there were 17 studies included with a total of 11474 infants, 5112 exposed to maternal biologic use, 3046 disease matched and 3316 CID free pregnancies (Table 1).
The overall proportion of LBW in the treated group was 10% (95% CI 0.07 to 0.12) the disease matched 8% (0.07 to 0.09) and the disease free group 4% (0.01 to 0.08) (Figure S7). No statistical differences were observed between disease matched and disease treated women (p=0.241), nor in disease free (p=0.079; Table S1).  Sub group analysis on anti-TNF-α use alone revealed no difference between groups outcomes (results not shown).
The SGA group included seven studies with 1638595 infants, 3342 born to women medicated with biologics during pregnancy and 10720 disease matched controls(Table 1). All of the SGA studies focused on anti-TNF-α biologics only. The proportion of SGA in the treated group was 6% (95% CI 0.02 to 0.10), the disease matched control 7% (0.02 to 0.11) and the disease free population 10% (0.10 to 0.10) (Figure S8). No differences were observed in proportions between disease matched compared with disease treated women (p=0.753), nor in comparison with disease free (p=0.170; Table S1).