Pregnancy weight gain may be associated with adverse pregnancy outcomes. The article aims to explore the relationship between weight change and pregnancy outcome in the Taiwanese pregnant women.The retrospective cohort study enrolled women with vertex singleton pregnancy at University-associated Hospital between 2011 and 2014. Pregnancy weight change was separated into 3 groups, based on the Institute of Medicine (IOM) guidelines: below (n = 221); within (n = 544); and above (n = 382). Analysis of variance, χ tests, generalized linear models, and logistic regression models were used for statistical comparisons.Pregnant women with weight change above IOM guidelines had a significant increase in both maternal and perinatal complications compared with normal controls (odds ratio [OR] 1.65, 95% confidence interval [CI] 1.03-1.98; P = .043; OR 1.45, 95% CI 1.01-1.87; P = .049, respectively). This finding was not found in pregnant women with weight gain below IOM guidelines. Moreover, age (OR 1.08, 95% CI 1.02-1.15; P = .0011), pre-pregnancy weight (OR 1.04, 95% CI 1.01-1.09; P = .0008), pre-pregnancy body mass index (BMI; OR 1.15, 95% CI 1.06-1.30; P < .0001), weight at the time of delivery (OR 1.05, 95% CI 1.02-1.13; P < .0001) and BMI at the time of delivery (OR 1.15, 95% CI 1.06-1.39; P < .0001), all contributed to increased maternal complications but not perinatal complications, whereas parity (OR 0.23, 95% CI 0.12-0.41; P < .0001) and gestational age (OR 0.50, 95% CI 0.35-0.62; P < .001) were associated with fewer maternal complications.Our study reconfirmed that for Taiwanese pregnant women, the approximate pregnancy weight gain recommended by IOM in 2009 was associated with the fewest maternal and perinatal complications. If approximate pregnancy weight gain cannot be attained, even less weight gain during pregnancy is still reasonable without significantly and adversely affecting maternal and perinatal outcomes in Taiwan.