In the fourth month of pregnancy, the normal amniotic fluid volume is around 200ml. Ultrasound examination shows that the vertical depth of the amniotic pool is 3-7cm and the amniotic fluid index is 8-18cm, indicating that the amniotic fluid is normal and suitable for the continued growth and development of the fetus. Pregnant women should continue to maintain good living habits and regular maternity checkups. When the amniotic fluid is too much, the pregnant woman’s abdomen may be enlarged and exceed the normal gestational age, and there may be fetal abnormalities, chromosomal abnormalities or twin pregnancies, diabetes, pregnancy combined with maternal and child blood type disorders. Therefore, it is necessary to check each case, regular ultrasound examination to understand the size of the fetus and the amount of amniotic fluid, testing blood sugar and urine routine, etc. to prevent infection. When the amniotic fluid is too low, the fetus has a reduced range of motion in the uterus and is prone to adhesions during organ development, leading to fetal malformations, including shoulder and neck, limbs, heart and lungs and other structures. Pregnant women can increase the amount of amniotic fluid through hydration and later choose whether to terminate the pregnancy according to the amount of amniotic fluid growth and fetal development. In order to ensure the health of pregnant women as well as the fetus, in the fourth month of pregnancy, pregnant women can hydrate more, eat foods that are good for fetal development and rich in calcium, such as eggs and beef, and eat more fresh vegetables and fruits to supplement nutrients and trace elements.