B-mode ultrasonography is a commonly used medical examination method. It uses ultrasound to image the human body to observe the growth and development of the fetus and discover potential problems. For pregnant women who are four months pregnant, B-ultrasound examination is very important. It can provide health information of the baby and help doctors evaluate the status of the pregnant woman and the fetus. [The most comprehensive and best sound quality in history] 32 sets of 100 must-listen late-pregnancy music for free. When conducting a B-ultrasound examination in the fourth month of pregnancy, the following aspects are mainly focused on: The growth and development of the fetus: B-ultrasound can measure the fetal Head circumference, abdominal circumference, femur length and other parameters to evaluate the growth of the fetus. Under normal circumstances, the head circumference of a four-month-old fetus is about 80-90 mm, the abdominal circumference is about 70-80 mm, and the femur length is about 40-50 mm. Through these data, doctors can determine whether the fetus is developing normally and whether there are problems such as growth retardation. Fetal organ structure: B-ultrasound can clearly display various organs of the fetus, such as heart, lungs, kidneys, brain, etc. The doctor will carefully observe whether the structure and function of these organs are normal and whether there are any abnormalities. For example, B-ultrasound can detect whether the four chambers of the fetal heart develop normally and whether there are problems such as congenital heart disease. The quantity and quality of amniotic fluid: During the fourth month of pregnancy, the quantity and quality of amniotic fluid are crucial to the health of the fetus. B-ultrasound can measure the depth and total volume of amniotic fluid to determine whether it is too much or too little. Too much amniotic fluid may be related to digestive problems in the fetus, while too little amniotic fluid may be related to kidney problems in the fetus. In addition, B-ultrasound can also detect particulate matter in the amniotic fluid, such as meconium, blood, etc., to evaluate the quality of the amniotic fluid. The condition of the pregnant woman\’s uterus and appendages: B-ultrasound can also observe the shape, size, position and condition of the pregnant woman\’s uterus and appendages (ovaries, fallopian tubes). This information is important for assessing the health of the pregnant woman and the development of the fetus. For example, B-ultrasound can detect whether there are tumors, polyps and other abnormalities in the uterus, as well as whether there are problems such as abnormal position of the placenta. In short, the B-ultrasound examination in the fourth month of pregnancy is a very important examination. Through it, we can understand the growth and development of the fetus, organ structure and function, the amount and quality of amniotic fluid, and the condition of the pregnant woman\’s uterus and appendages. If any abnormalities are found, doctors will take appropriate measures to ensure the health and safety of mother and baby. It should be noted that although B-ultrasound is a commonly used inspection method, it also has certain limitations. It can only provide image information and cannot perform tissue biopsies or determine a firm diagnosis of certain diseases. Therefore, when performing B-ultrasound examination, it is necessary to combine other examination methods and comprehensive judgment with clinical manifestations to obtain more accurate diagnostic results. Finally, pregnant women should choose a regular medical institution and follow the doctor\’s guidance and recommendations when undergoing B-ultrasound examination. At the same time, pregnant women should maintain good living habits, eat a balanced diet, and avoid bad habits such as smoking and drinking to promote the healthy development of the fetus.