Obstetric ultrasonography can be divided into three categories: ① Class I prenatal ultrasonography: including early pregnancy and general ultrasonography of middle and late pregnancy; ② Class II prenatal ultrasonography: including fetal ultrasonography of middle and late pregnancy (i.e. ultrasound prenatal screening), mainly performed at 16 to 24 weeks of gestation; ③ Class III prenatal ultrasonography: including systematic fetal ultrasonography of middle and late pregnancy (i.e. ultrasound prenatal diagnosis) and targeted (purpose-specific) ultrasonography. It is important to clearly inform the pregnant women that obstetric ultrasound cannot detect all fetal malformations. Fatal fetal anomalies that should be detected by ultrasound at 18 to 24 weeks of gestation include anencephaly, severe brain expansion, severe open spina bifida, severe abdominal wall defects and visceral ectopia, single-chambered heart, and fatal chondrodysplasia.
I. Personnel requirements
Physicians engaged in prenatal ultrasound examination must have a license to practice medicine; bear the system of fetal ultrasound examination of middle and late pregnancy physicians should also meet one of the following conditions: ① college degree or above, and has a professional and technical title of ultrasound medicine above the intermediate level, received systematic training in prenatal diagnosis; ② more than 5 years in this position in obstetrics and gynecology ultrasound examination, received systematic training in prenatal ultrasound diagnosis.
Second, the equipment requirements
Real-time ultrasound diagnostic instrument. Units that undertake fetal ultrasound examination of mid- and late-term pregnancy system should have more than one color Doppler ultrasound diagnostic instrument with image recording equipment.
Third, ultrasound examination standards
(A) general prenatal ultrasound examination of early pregnancy (level I prenatal ultrasound examination).
1, examination content: determine intrauterine pregnancy, diagnose multiple pregnancy, assess gestational week, exclude pregnancy-related abnormalities (ectopic pregnancy, gravida, vaginal bleeding), exclude other gynecological disorders (pelvic masses, uterine malformations), assisted chorionic villus biopsy, etc.
2.Examination methods: transabdominal ultrasonography; transvaginal ultrasonography.
3.Examination items.
Fetal sac (size, shape, position)
Fetal bud (head-rump length, fetal heartbeat)
uterus, both adnexa
(II) General prenatal ultrasound examination of middle and late pregnancy (Class I prenatal ultrasound examination).
1.Examination content: assessment of fetal growth parameters (more than three weeks apart), assessment of amniotic fluid, placenta, determination of gestation number and fetal position.
2.Examination items: biparietal diameter, femoral length, abdominal circumference, fetal position, fetal heart rate and rhythm, placenta, amniotic fluid and other general morphological indicators; estimation of fetal size.
3. Precautions: In the implementation of general prenatal ultrasound examination of middle and late pregnancy, if anencephaly and other malformations are found, the ultrasound report should be specified and referred for confirmatory examination.
(iii) Fetal ultrasound examination for middle and late pregnancy (level II prenatal ultrasound examination).
1. Examination content: In addition to the content of level I prenatal ultrasound examination, it should include: morphological observation of major fetal organs, such as certain important structures in the skull, four-chambered heart section, liver, stomach, kidney and other organs in the abdominal cavity, and cursory screening for serious fetal lethal malformations.
The lethal malformations that should be diagnosed at 18-24 weeks of gestation include anencephaly, severe brain expansion, severe open spina bifida, severe thorax, abdominal wall defect visceral exostosis, single-chambered heart, and lethal chondrodysplasia.
2. Examination items: In addition to the items included in the level I prenatal ultrasound examination, the following anatomical aspects should be included at a minimum.
Head: skull, brain, midbrain, lateral ventricles, thalamus.
Facial: lip.
Heart: four-chamber cardiac section.
Spine: cervical, thoracic, lumbar, and sacrococcygeal segments.
Abdomen: integrity of the abdominal wall, liver, stomach, both kidneys, and bladder.
Fetal umbilical cord and its attachment site.
Other anatomical structures can be examined when the fetal position allows.
3.Note: The fetal examination should at least check the above fetal anatomical structures. However, sometimes due to the fetal position, low amniotic fluid and maternal factors, the ultrasound examination does not show these structures well, and the ultrasound report should indicate which structures are not clearly shown.
4. Time of examination: it is more appropriate to be performed at 18-24 weeks of gestation.
(4) Systematic fetal ultrasonography in middle and late pregnancy (level III prenatal ultrasonography).
(1) Indications: Systematic fetal ultrasonography should be performed promptly when fetal malformation is detected or suspected or when there are high-risk factors for fetal malformation in general prenatal ultrasonography and fetal ultrasonography in middle and late pregnancy. If available, a systematic fetal ultrasound should be performed at 18-24 weeks of gestation.
2.Examination items.
(1) Basic items: Biparietal diameter, head circumference, cranial integrity, description of fetal number, fetal orientation and fetal size, whether the umbilical cord is wrapped around the neck, maximum depth of amniotic fluid should be observed and reported. Describe the position of placental attachment, placental thickness, and placental maturity.
(2) Cranial: the position of the midline of the brain, whether the lateral ventricles are widened, the morphology of the cerebellum and the integrity of the cerebellar earthworms.
(3) Facial region: the continuity of the upper lip skin should be observed and reported.
(4) Spine: whether the vertebral arrangement of each segment of the spine is normal, whether the curvature of the spine is normal, whether the vertebrae are arranged in parallel, and whether there is any interruption of vertebral continuity should be observed and reported.
(5) Thorax: The lungs and heart should be observed and reported for normal position.
(6) Heart: The fetal heart rate should be measured and the rhythm, heart size, four-chamber heart section, right and left atrial symmetry, and right and left ventricular outflow tract section should be described, as well as the selection of echocardiography based on the indications for echocardiography.
(7) Abdominal organs: description of the integrity of the abdominal wall, liver, stomach, both kidneys, and bladder morphology, and umbilical vessels.
(8) Extremities: measure the femur, and the humerus, ulnar radius, femur, and tibiofibula of the extremities should be observed and reported.
(5) Targeted examination.
Targeted examination should be based on systematic fetal ultrasound examination, and purpose-specific examination should be conducted for special problems of fetus and pregnant women, such as measurement of zona pellucida, and more detailed ultrasound examination of fetal nervous system and cardiovascular system.
(vi) Ultrasound examination report.
The diagnostic ultrasound report should be consistent with the above criteria, and positive results should be documented with images. Cases where the evaluation of fetal anatomy is limited because of fetal and maternal factors should be recorded on the report, and follow-up examinations should be performed when necessary.
IV. Safety
The current scientific findings indicate that fetal prenatal ultrasonography is safe. The general principle is to master the indications and obtain the necessary diagnostic information under the minimum ultrasound exposure conditions allowed by the regulations.
V. Quality control
Implementation of personnel and equipment requirements, continuing education regulations, and regular statistics on prenatal ultrasound diagnostic compliance.