At 4 months of age, the fetal body organs are not fully developed, so it is generally not recommended for pregnant women to undergo 4D ultrasound examination at this time, as it may not be able to clearly determine whether the fetus has developmental abnormalities and the results obtained are not accurate enough. 4D ultrasound examination is a major screening test, which is usually performed at 20-24 weeks of pregnancy. It is mainly used to diagnose whether the fetus has obvious malformations, such as ventricular septal defect, partial loss of limbs, cleft lip and palate, cleft abdominal wall, hydrocephalus, anencephaly, spina bifida, heart malformation and urinary system malformation through ultrasound examination. The 4D ultrasound examination can not only see the development of the fetus, but also learn about the physical condition of the pregnant woman. If a 4D ultrasound is performed at 4 months of pregnancy, some of the fetal organs may be missed because they are not yet fully developed. In addition, Down’s syndrome screening is also required at 4 months of pregnancy to effectively prevent the birth of children with Down’s syndrome. During pregnancy, pregnant women should pay attention to stay away from radiation, avoid stimulation by toxic and harmful gases, and have regular maternity checkups. It is also necessary to pay attention to rest, avoid exertion and keep a happy mood during pregnancy to ensure normal fetal growth and development.