This figure shows crude mean birth weight (with 95% CI) by birth order for infants in families with at least three births.

Family groups are specified on top of each panel. Control families (6 ) are included in all panels.

Symbols: 6 = Infants in families without registered congenital malformations (‘control’ families; n = 195,035); Families with one or two malformed infants (‘case’ families; numbers indicated above each panel): ) = the malformed infants; * = their non-malformed siblings.