Amniotic fluid index of 66mm may be more dangerous. Amniotic fluid index of 66mm, has been lower than the normal amniotic fluid index standard (8~18cm), amniotic fluid index less than or equal to 8cm, for amniotic fluid is low, amniotic fluid index less than or equal to 5cm, diagnosis of amniotic fluid is too low. Low amniotic fluid may indicate fetal abnormalities, such as low fetal urine due to fetal anomalies, amniotic membrane diseases such as premature rupture of membranes leading to amniotic fluid exposure, placental dysfunction such as expired pregnancy, etc., or chronic hypoxia due to fetal growth restriction. At this time, pregnant women should be timely obstetric examination, daily fetal movement counting, and regular monitoring of amniotic fluid volume. At the same time, increase the amount of water consumed by the pregnant woman and relax her mood to prevent the amniotic fluid volume from dropping due to stress. Pregnant women with an amniotic fluid index of 66mm should seek timely medical attention to comprehensively assess the condition of the fetus under the guidance of a doctor, and carry out targeted observation or treatment to avoid causing harm to the fetus or the mother.