请检查下面这段话的检查语法错误进行修改和润色修改部分要标注出来：The study also has limitations First although even though several covariates were adjusted for such as maternal age pre-pregnancy BMI educational attainment marital sta

The study also has limitations. First, although several covariates such as maternal age, pre-pregnancy BMI, educational attainment, marital status, employment status, birth gender, and conception season were adjusted for, other confounding factors could not be controlled due to the unavailability of information. For example, unavailable information on the nutritional status and gestational weight gain of the participants might affect the development of GDM. Likewise, the lack of information about previous diabetes mellitus could lead to an overestimation of the occurrence of GDM. Second, the association between inflammatory markers and GDM may not be specific enough because various factors may affect inflammation. Third, all the subjects in our study were from Foshan city, so the population we selected was not representative enough, which may lead to biased results. (The only error was the repetition of "therefore" in the original text, which has been removed here.)