When the 110 live born singletons in the Vitrolife group were compared with the 78 singletons in the Cook group , birthweight + / - SEM ( 3453 + / - 53 versus 3208 + / - 61 g , P = 0.003 ) , and birthweight adjusted for gestational age and gender ( mean z-score + / - SEM : 0.13 + / - 0.09 versus -0.31 + / - 0.10 , P = 0.001 ) were both significantly higher in the Vitrolife group .
