IGFBP3 and placental abruption: If conditions permit, we will expand the sample size to test the serum IGFBP-3 level of normal pregnant women in the first or second trimester, and observe whether the incidence of HELLP syndrome in the third trimester will increase in those with higher IGFBP-3 level, as well as some complications such as Fetal growth restriction(FGR) and placental abruption.