Per- and polyfluoroalkyl substances (PFAS) are commonly found in consumer products, exposure is ubiquitous. We examined associations between maternal serum concentrations of six PFAS during pregnancy and birth outcomes in 130 mother-child pairs from the North Carolina-based TESIE Study (2009-2011). We used multivariable and weighted quantile sum (WQS) regression models to estimate total and sex-specific associations between birth outcomes and individual and cumulative exposure to maternal serum PFAS concentrations, respectively. Among male offspring, linear and branched perfluorooctane sulfonic acid (n-PFOS and Sm-PFOS, respectively), linear perfluorooctanoic acid (n-PFOA), perfluorohexane sulfonic acid (PFHxS), and perfluorononanoic acid (PFNA) were inversely associated with birth weight and n-PFOS, n-PFOA, Sm-PFOS, and PFNA were inversely associated with gestational age at birth. Among female offspring, only n-PFOA was inversely associated with birth weight, and n-PFOS, n-PFOA, and perfluorodecanoic acid were inversely associated with gestational age at birth. Cumulative prenatal exposure to the six PFAS was inversely associated with birth weight and gestational age at birth [β = -248.6, 95% CI: -454.9, -42.2 grams and β = -6.3, 95% CI: -11.4, -1.3 days, per weighted quartile increase, respectively] among male offspring, with n-PFOA being the most important PFAS for both birth outcomes according to the WQS weights. Among female offspring, cumulative prenatal exposure to PFASs was positively, but imprecisely, associated with birth weight [β = 76.2, 95% CI: -103.3, 255.7 grams per weighted quartile increase] and not associated with gestational age at birth. These results suggest that male offspring may be more susceptible to individual and cumulative prenatal exposure to PFASs than females and that offspring sex is an effect measure modifier of the association between maternal serum PFAS concentration and birth outcomes.