A fetus that is two weeks smaller than the gestational week is not necessarily developmentally delayed. With the continuous increase of gestational weeks, the fetus will further grow and develop, the size of the fetus timely assessment, can assess the development of the fetus, some pregnant women with irregular menstruation, the calculation of gestational weeks is wrong, which can lead to the size of the fetus is smaller than the normal level of gestational weeks for two weeks, this is not a delay in the development of the fetus should be corrected in time to correct gestational weeks, and then assessed again. Some pregnant women have regular menstruation, and the calculation of gestational weeks is accurate, in this case, the development of the fetus is smaller than the gestational weeks for two weeks, first of all, consider the genetic factors, except for the cause of the short stature of the parents, it should be considered that there is developmental delay, it should be clarified in a timely manner, whether the mother has gestational hypertension syndrome, anemia in pregnancy, and whether there are malformations of the fetus and other conditions. If the pregnant woman or the fetus has any abnormalities, she should receive standardized treatment as soon as possible, so as to avoid delaying the condition, which may lead to adverse pregnancy outcomes.