Abstract:OBJECTIVE To investigate the relationship between different blood calcium levels and Hypertensive Disorder Complicating Pregnancy (HDCP) and complications, and to study the relationship between the two groups in pregnant women with different age,in order to providea theoretical basis for preventing the occurrence of HDCP and complications. METHODS Based on the big data platform of the First Hospital of Shanxi Medical University, a total of 958live single-birth pregnant women between January2012 and June 2017, as the research object, 138women of HDCP were treated as cases, while 820women without HDCPwere treated as controls. Based on the medicalbig data platform,the general demographic characteristics of pregnant women, pregnancy complications and prenatal blood calcium levelsand so on were obtained. Unconditional logistic regression was used to analyze the relationship between different blood calcium levels and HDCP and complications, and the relationship between the two in different age groups was analyzed separately. RESULTS The incidence of HDCP was 14.41%(138/958).After adjusting for various factors, compared with those with blood calcium levels≥2.2mmol/L, low blood calcium(<2.2mmol/L) was a risk factor for HDCP (OR=2.037, 95%CI: 1.399~2.965). After stratified byage, pregnant women with age≥35, low blood calciumwas a risk factor for HDCP(OR=2.516, 95%CI: 1.478~4.284), mainly can increase the risk of HDCP with pregnancy subclinical hypothyroidism (SCH) (OR=2.728,95%CI: 1.228~6.059)and no association was found in the age<35 group. CONCLUSIONS Low blood calcium(<2.2mmol/L) is a risk factor for HDCP. Low blood calcium in pregnant women with age≥35 can increase the risk ofHDCP,mainly can increase the risk of HDCP with SCH. Further research is needed in the future to clarify the underlying mechanisms.