Recent data suggests that abnormal maternal pre-pregnancy body mass index (BMI) or gestational weight gain (GWG) is associated with unfavorable delivery outcomes. However, limited clinical evidence is available to support this correlation in China. Participating 510 mother-infant pairs were recruited from the Shanghai First Maternity and Infant Hospital, China, between January 1st and 30th 2016. Maternal pre-pregnancy BMI was categorized according to the China's classification and GWG according to the 2009 Institute of Medicine recommendations (IOM). Linear regression tested the associations between pre-pregnancy BMI or GWG and length of gestation, birthweight, length, and head circumference. Logistic regression assessed the associations between pre-pregnancy BMI or GWG and macrosomic, small- (SGA) and large- (LGA) for-gestational-age infants. Overweight/obese women showed increased length of gestation and birthweight, but did not have a higher risk of macrosomic and LGA infants compared with normal weight women. Women with excessive GWG showed increased length of gestation, birthweight, length, and head circumference, and were more likely to deliver macrosomic and LGA infants compared with women with adequate GWG. Although a relatively low proportion of women from Shanghai area are overweight/obese or exhibit excessive GWG, both high pre-pregnancy BMI and excessive GWG influence perinatal outcomes.