In the last decade, perinatal medicine has developed considerably, and there is an increasing collaboration between different specialties, all aiming to provide a comprehensive examination and evaluation of the fetus during the perinatal period, in order to predict the postnatal condition and develop a treatment. The majority of genetic congenital malformations can be diagnosed prenatally by ultrasonography.
At present, with the development of ultrasound technology, various congenital fetal malformations can be detected from early and mid pregnancy, which plays an important screening role in eugenics, and ultrasonography has become the preferred method of prenatal diagnosis.
All pregnant women need a routine ultrasound examination at mid-term pregnancy (usually around 18 weeks), (measurement of fetal size, placental position, and exclusion of major congenital malformations of the fetus).
I. High prevalence of fetal malformations.
1, family history of giving birth to malformed children and parents themselves as patients with physical disorders.
2, chromosomal abnormalities, (such as triploidy 21, triploidy 13, triploidy 18, chromosomal deletions ……)
3, Maternal.
(1) All types of diabetes mellitus (especially insulin-dependent in early gestation).
(2) Connective tissue diseases (for systemic lupus erythematosus, rheumatoid arthritis, Rh hemolysis ……).
(3) Infectious diseases (certain viral infections in mid-pregnancy such as rubella, toxoplasma infection, influenza ……).
(4) Treatment with certain drugs in early pregnancy.
(5) Chronic alcoholism.
Advanced maternal age and history of abnormal pregnancy (excessive amniotic fluid, too little amniotic fluid, previous miscarriage, history of stillbirth).
Second, several factors related to the detection rate
1. There are many types of congenital fetal malformations, and almost all systems of the fetus can be involved.
The basis of ultrasound image diagnosis is the morphological changes of the fetus, and the detection rate is high for those with large morphological changes, but not easy to detect those with small morphological changes.
2.The resolution of the instrument.
3.The technical proficiency of the examiner.
4.Other factors (gestational week, amniotic volume, fetal position, maternal factors).
3.Ultrasound diagnosis of fetal malformation
1.Defects of central nervous system.
The incidence accounts for the first place of fetal malformation. The manifestations are diversified according to the different parts of involvement.
(1) Anencephaly
Ultrasound image features.
a Lack of a garden-shaped cranial halo.
b A “nodular” mass can be seen at the cephalic end of the fetus, and the orbit and nasal bone can be found above it.
c The brain tissue is atrophied, and some anencephalic infants have a hypoplastic brain tissue surrounded by a meningeal sac floating in the amniotic fluid.
d It is often combined with cervicothoracic spina bifida and amniotic fluid overload. The diagnosis can be confirmed at 14-15 weeks of gestation.
(2) Hydrocephalus
There are two types of hydrocephalus: ventricular system hydrocephalus and extra-ventricular system hydrocephalus. If the fluid is in the extracerebral space (between the brain and the dura mater), it is called extracerebral fluid, also known as hydranencephaly.
Ultrasound image characteristics.
a Mild: The ventricles are mildly enlarged and contain dark areas of fluid, with reflective intense light clusters (choroid plexus) common within the fluid. The ventricular rate is >0.5. The biparietal diameter corresponds to the gestational week.
b Late stage: fetal biparietal diameter is significantly larger than gestational age, cephalic circumference diameter is significantly larger than fetal abdomen, thoracic circumference, disproportionate head to body, the vast majority of fetal intracranial fluid dark areas, midline drifting within the cerebrospinal fluid. Severe ventriculocephalus with thinning of brain tissue under pressure.
c Hydrocephalus: a large amount of cerebrospinal fluid is seen surrounding the brain tissue or only the brainstem structures are seen, and structures above this level (including the brain, ventricles and cerebral curtain) are absent.
(3) Cerebrospinal bulge
(1) Meningeal bulge
Ultrasound image features.
a. In the midline of the fetal skull, a cystic mass containing a dark area of fluid is bulging.
b. Bone defect at the bulge.
c. The cyst is surrounded by a cystic wall, sometimes thicker (containing skin).
②Spinal membrane bulge
Ultrasound image features.
a, a cystic mass protruding from any part of the midline of the spine, containing a dark area of fluid, floating in the amniotic fluid.
b. Bone defects at the spinal bulge.
c, a very thin cystic wall with only a membrane.
(4) Meningeal brain expansion
Ultrasound image features.
①, the midline position of the fetal head, a protruding mass is visible, the mass has a thick wall, contains skin, and the boundaries of the mass are clear.
(2) The cranial wall is defective at the connection between the mass and the fetal head.
③, some or all of the brain tissue is seen within the mass, with a tortuous solid structure.
(4) The cranial halo is reduced or not planned, the bone wall is unevenly thick and thin, and the biparietal diameter may be small.
(5), microcephaly
The diagnosis can be established if the ultrasound image shows that the fetal biparietal diameter, head circumference and head area are lower than three standard deviations or more of that gestational age. There are many causes of microcephaly, often chromosomal recessive inheritance, but also environmental factors can be damaged.
Spina bifida
Ultrasound images show spina bifida differently depending on the severity, mildness, location, and morphology of the lesion.
① Mass type The affected area of spina bifida appears as a raised mass and is divided into two types of images.
a. Parenchymal masses Mostly elevated disorganized bones, substantial, and strong echogenicity.
b. Cystic mass The affected area is a small sac protruding from the spine with a dark area of fluid, where the two light bands of the spine are partially interrupted by the absence of cerebrospinal fluid.
In spina bifida, the two light bands are broadened and the bones are thickened and misaligned. The spinal column is shortened and widened.
Bifurcation type Bifurcation of the spine to the sacrococcygeal region.
Note: The most suitable time for ultrasound detection of spina bifida is 17-18 weeks of pregnancy, so the amount of amniotic fluid is relatively high and easy to detect.
2. Digestive system malformations and abnormalities
(1) Ultrasound diagnosis of gastrointestinal atresia
(1) Esophageal atresia is manifested as
a, no fluid-containing gastric alveoli or intestinal canal can be found in the fetal abdominal cavity.
b, combined with excess amniotic fluid.
Gastric pyloric obstruction can be seen as “single bubble” gastric dilatation, combined with excessive amniotic fluid.
If the atresia is in the duodenum, a “double vesicle sign” is seen in the transverse section of the upper or middle abdomen of the fetus.
④ jejuno-ileal atresia
a. The fetal abdomen is bulging and the abdominal circumference is increasing.
b. Many dilated fluid-filled intestinal rings can be seen in the fetal abdomen.
c. Mostly combined with excessive amniotic fluid.
d. The intestinal canal is very active peristalsis.
⑤ Anal atresia
a. The fetal abdomen is enlarged and a “double lobe sign” is seen in the lower abdomen, containing a liquid dark area.
b. The diaphragm in the “double lobe” may be centrally or partially located, and the diaphragm may be complete or incomplete.
c. The rectum may be dilated and thickened.
d. Usually combined with amniotic fluid.
(2)`Hernia
① Ultrasound manifestation of umbilical hernia.
a. There is a defect in the umbilical part of the fetal abdominal wall.
b. A mass protruding from the abdominal wall, containing fetal viscera and ascites.
c. The hernia sac is wrapped around the mass and is thin.
d. Sometimes a pulsating fetal heart can be seen inside the hernia sac.
e. It is often combined with excessive amniotic fluid.
② Ultrasound manifestations of diaphragmatic hernia.
a. In addition to the heart, a fluid-filled or attenuated intestinal canal can be seen next to the heart in the fetal chest cavity.
b. Abnormal fetal activity in the uterus, hiccups or vomiting movements, and frequent mouth opening and tongue vomiting.
c. Often combined with excessive amniotic fluid.
3.Fetal ascites and hydrothorax
(1) Fetal ascites: there is a dark area of varying degrees of liquid between the fetal abdominal wall and internal organs.
(2) Fetal hydrothorax: there is a dark area with varying amount of liquid between the chest wall and fetal heart, in which the beating fetal heart can be seen, and the compressed lungs on both sides can be seen above the fetal heart.
(3) Fetal hydrothorax and ascites coexist: there is fluid in both abdominal and thoracic cavities, and the diaphragm is visible in a line between the thoracic and abdominal cavities, with the fetal heart and lungs attached to the upper thoracic cavity. The abdominal surface is connected with liver, spleen, intestinal canal and other internal organs.