The fetal lung maturity is determined by the following methods: 1. amniotic fluid is drawn and the ratio of lecithin to sphingomyelin in the amniotic fluid is measured. a value greater than 2 indicates fetal lung maturity. the ability to measure amniotic fluid phosphatidylglycerol also indicates fetal lung maturity. this value is more reliable and the amniotic fluid foam shock test is performed. 2. a complete foam ring on the surface of the tube fluid indicates fetal lung maturity. 3. fetal lung maturity can be presumed if the following conditions are met. The first time the fetal heart is heard by stethoscope, it has been 20 weeks, and the first time the fetal heart is heard by Doppler, it has been 30 weeks; the first time the blood and urine HCG are positive, it has been 36 weeks; according to the head-rump diameter length measured at 6-11 weeks of pregnancy, it is presumed that the current gestational week has reached 39 weeks. 4. According to the fetal diameter measured at 12-20 weeks, it is presumed that the current gestational week has reached 39 weeks.