Urinary system malformations
(1) Renal hypoplasia or renal agenesis.
(2) Hydronephrosis of the renal pelvis.
(3) Polycystic kidney.
(4) Urethral obstruction causing the bladder to dilate and fill the abdominal cavity.
Abnormalities of the fetal skeletal system
Abnormalities in skeletal development can be seen in the head and extremities.
Cleft lip and cleft palate (cleft lip and cleft palate) In cleft lip, the palatal plate is intact, and in cleft lip and palate, there is incomplete growth of the nose and teeth. Severe cleft palate can pass to the pharynx and seriously affect breastfeeding. Prenatal diagnosis is difficult. B-mode ultrasound can only detect obvious cleft lip and palate, and fetal microscopy can diagnose it directly, but it is more damaging. Plastic orthopedic treatment in the neonatal period is more effective.
Other malformations include: maxillofacial lymphangiectasia, cervical lymphangiectasia, osteogenesis imperfecta, etc.
Twin fetus-related malformations
Twin transfusion syndrome (TTTS) is a serious complication of monochorionic monozygotic twin fetuses with double amniotic sacs. TTTS occurs in approximately 15% of monochorionic multiple pregnancies and is primarily due to the presence of a vascular anastomosis between the twins in the placenta. The recipient fetus presents with increased circulating blood volume, excess amniotic fluid, enlarged heart or heart failure with edema, while the donor has decreased circulating blood volume, low amniotic fluid and growth restriction. The morbidity and mortality rate of severe TTTS is as high as 80-100%.
Twin Reversed Arterial Perfusion Sequence (TRAP), also known as anencephaly, is a condition in which one of the twin fetuses has an absent, residual or non-functioning heart. If left untreated, a normal fetus may develop heart failure and die. The main treatment is radiofrequency ablation for fetal reduction.
Monochorionic monoamniotic sac twins: Because the two fetuses share one amniotic cavity and there is no fetal membrane separating the two fetuses, intrauterine accidents due to cord entanglement and knotting are more likely to occur, which is a very high risk twin pregnancy.
Other conditions include: selective intrauterine growth restriction and conjoined twins.
Chromosomal abnormalities
The more common autosomal abnormalities include Down syndrome (trisomy 21), trisomy 18, and sex chromosomal abnormalities such as Turner’s syndrome. Amniotic cell sex chromosome examination can help diagnose sex linked inheritance disease (sex linked inheritance disease) inborn metabolic abnormalities: such as black montanous family dementia, galactosemia, etc.
Genetic disorders.
(1) Monogenic genetic diseases: diseases caused by mutations or abnormalities in only one pair of genes. The vast majority manifest as defects in enzymes. Clinically, they are called inborn metabolic disorders. For example, dementia of the black mask family, galactosemia, etc.
(2) Polygenic genetic disorders: mutations in more than two pairs of multiple gene pairs. Each pair of genes is co-dominant, and the effect of each pair of genes is minor, but several pairs of genes act to accumulate or form a distinct effect, which manifests a cluster of symptoms clinically, mainly manifesting as some congenital malformations, such as cleft lip, cleft palate and deformed foot, spina bifida, anencephaly, neural tube malformation, pyloric stenosis, congenital hip dislocation, congenital heart disease, etc.
Etiology and mechanism
Fetal malformations are caused by a variety of factors, and many of them are still in the “suspected” stage, only presumed to be causative factors or the causative mechanisms are unknown.
In general, the main causes of fetal malformation include
1, radiation damage: mainly occurs in early pregnancy when radioactive substances are exposed.
2, drug teratogenicity: teratogenic drugs are taken in early pregnancy.
3, genetic factors: such as trisomy 21, hemophilia, etc.
4, pathogenic biological infection: such as TORCH, syphilis spirochete, HIV infection, etc.
5.Mechanical stimulation: such as abdominal trauma, medical source of early pregnancy intervention, etc.
6, bad postnatal habits: drug addiction, smoking, alcoholism, etc.
7, other causes.
Examination methods
1.Imaging examination
Ultrasonography: Ultrasonography is the most important examination method recognized for screening and diagnosing fetal structural malformations, especially in the examination of fetal heart anomalies, which has important value. Ultrasonography is also an important tool for routine prenatal screening. In addition, ultrasound examination of fetal blood flow changes has become an important method to detect intrauterine well-being of the fetus.
Fetal magnetic resonance examination: magnetic resonance has a broad prospect for application in obstetrics because of its multi-bit imaging, high soft tissue resolution, no radiation, and safety to the fetus. It has also become an important verification and supplementary diagnostic tool for fetal abnormalities found by ultrasonography in prenatal diagnosis. Especially, it has more outstanding performance in diagnosing fetal central nervous system abnormalities, such as identifying cerebral hemorrhage.
Others: Fetal CT examination is currently limited to the examination of diseases such as fetal osteogenesis malformation. Because of its radioactivity, it is not widely used at present.
2.Interventional diagnosis
Chorionic villus test: Chorionic villus test is performed after 50 days of pregnancy by taking the vaginal or abdominal chorionic villus for chromosomal or other tests to check whether the fetus has chromosomal disorders, but this method has the risk of miscarriage and may lead to fetal mutilation.
Amniotic fluid and cord blood examination: Amniotic fluid examination and percutaneous fetal cord blood examination can be used for fetal sex chromosome examination, karyotype analysis, whole gene sequencing, maternal and fetal blood group incompatibility, determination of fetal maturity, fetal kidney function, amniotic fluid cell culture for enzyme analysis and various biochemical examinations of amniotic fluid, etc.
Fetal microscopy: The main function of fetal microscopy is to directly observe the fetal body surface, placenta-fetal surface, umbilical cord, etc. It is also feasible to collect amniotic fluid, fetal blood and fetal body surface tissues (skin and muscle tissue, etc.); such as direct observation and diagnosis of congenital fetal malformations with obvious shape changes, including cleft lip, cleft palate, polydactyly, limb-finger malformation syndrome, osteochondral dysplasia, open neural tube malformation, visceral ectropion, umbilical bulge, abdominal wall cleft and visceral turn-out, conjoined twins, multiple limbs, large hemangioma, external genital malformation, etc. Fetal biopsy is used to diagnose severe genetic skin disorders such as macrovesicular dermatolysis, ichthyosiform erythrodermatitis, lichen planus or lichen planus. Fetal liver tissue biopsy is performed for those with fetal liver disease or disease related to fetal liver enzyme metabolism. Fetal muscle tissue biopsy, such as fetal pseudohypertrophic muscular dystrophy, progressive spinal muscular atrophy, etc. Fetal microscopic extraction of umbilical cord blood: to diagnose hemoglobin disorders such as thalassemia and sickle cell anemia, hemophilia, chronic sarcoidosis, galactosemia, mucopolysaccharide accumulation disorder, maternal and child blood group incompatibility, genetic immunodeficiency disorders, intrauterine viral infection of the fetus, etc.
3.Chromosome and genetic examination
Cytogenetic and congenital metabolic abnormalities examination: mostly performed in the middle of pregnancy.
(1) Chromosome abnormalities: karyotype analysis technique is the gold standard for diagnosing chromosome number or structure abnormalities. Karyotype analysis by amniotic fluid cell culture can diagnose chromosome (autosomes and sex chromosomes) number or structure abnormalities. The more common autosomal abnormalities include Down syndrome (trisomy 21) and trisomy 18, and sex chromosome abnormalities include Turner`s syndrome. The examination of sex chromosomes in amniotic fluid cells helps to diagnose sex-linked genetic diseases.
(2) Congenital metabolic abnormalities: Certain enzymes are measured by amniotic fluid cell culture to diagnose abnormalities or defects of certain proteins or enzymes caused by genetic mutations. For example, amidohexokinase A activity can be measured to diagnose dementia of the black monk family caused by lipid accumulation, and galactose-1-phosphate urophthalide transferase can be measured to diagnose galactosemia, etc.
(3) Genetic diseases: Fetal DNA extracted from amniotic fluid cells for direct or indirect analysis or detection of a gene. In recent years, it has been possible to apply the interplay of synthetic DNA chemistry, recombinant DNA technology and molecular cloning research for genetic diagnosis of genetic diseases, such as sickle cell anemia and phenylketonuria. At present, the genetic diseases that can be prenatally diagnosed in China include thalassemia, phenylketonuria, hemophilia A and B, pseudohypertrophic myotonic dystrophy, etc.
(4) Genetic engineering for prenatal diagnosis: Molecular biology techniques have been widely used for prenatal diagnosis of genetic diseases such as sickle cell anemia, Bart’s edema fetus, HBH disease and other gene carriers of alpha globulinogenic anemia, beta globulinogenic anemia, hemophilia A, alpha-antitrypsin deficiency phenylketonuria, Duchenne progressive myotonic dystrophy, retinoblastoma (5) Mother’s blood fetal disease, Wilson’s disease, Huntington’s chorea, etc.
(5) Maternal blood fetal free DNA fragmentation test (non-invasive DNA test): a test method developed in recent years to check fetal chromosome number abnormalities by examining special fetal free DNA fragments in maternal blood, which has been widely accepted because of its non-invasive nature and high accuracy rate.