Intrauterine growth restriction (fetal growth restriction) is a lag in growth, weight and other fetometric indicators from the standard average for a specific gestation period. It often proceeds asymptomatically, may manifest itself with a small increase in the weight of a pregnant woman, a small circumference of the abdomen, too active or rare movement of the child. For diagnosis, ultrasound of the placenta, fetometry, CTG, Dopplerography of placental blood flow are performed. Complex medical treatment with the appointment of angioprotective, rheological drugs, tocolytics, antihypoxants, membrane stabilizers. In case of ineffectiveness of therapy and aggravation of disorders, early delivery or cesarean section is recommended.
Intrauterine growth restriction is said in situations when its mass is 10 or more percentiles lower than the standard. According to medical statistics, IUGR complicates the course of every tenth pregnancy, is the cause of various diseases of the fetus and newborn. In 70-90% of cases, the delay develops in the third trimester in the presence of maternal diseases, placental pathology and multiple pregnancy. 30% of children with hypotrophy are born prematurely, only 5% of newborns have signs of full-term pregnancy. Fetal growth retardation is more often diagnosed in patients younger than 18 years and older than 30 years. The probability of this pathology is especially high in age-related primiparous.
Any lag of the child in intrauterine growth and maturation is associated with insufficient intake or assimilation of nutrients and oxygen. The immediate causes of such disorders may be pathological changes in the fetoplacental system, the organisms of the mother and fetus, fetal membranes. Usually, developmental intrauterine growth restriction occurs under the influence of factors such as:
- Mother’s illness. A limited supply of oxygen and nutrients is observed in anemia and other blood diseases, pathological conditions accompanied by vascular spasm and heart failure (hypertension, symptomatic arterial hypertension, gestosis, liver and kidney diseases). The risk of delay is increased in patients with gynecological pathology, endocrinopathies (diabetes mellitus, hypothyroidism), who have suffered acute infections.
- Fetal lesion. Incoming nutrients are absorbed worse if a child has genetic defects (Patau syndrome, Down syndrome), malformations of the central nervous system, heart, kidneys. The risk of abnormalities and developmental delay increases with intrauterine infection of the fetus with infectious agents — intracellular parasites (toxoplasmas, mycoplasmas), herpes viruses, rubella, HIV, Coxsackie, hepatitis B and C.
- Damage to the placenta and fetal membranes. Damage to more than 10-15% of placental tissue is accompanied by the formation of fetoplacental insufficiency — the key reason for the delay in intrauterine maturation of the child. The fetus experiences oxygen starvation with placental infarctions, its premature detachment or involution. Fetal growth may be impaired with chorioamnionitis, umbilical cord pathology (presence of true nodes, inflammation), lack of water, formation of amniotic band syndrome, etc.
- Conflict in the mother-child system. Isoimmune incompatibility of a fetus and a woman with different blood groups or Rh factor is manifested by hemolysis of fetal erythrocytes and the formation of toxic indirect bilirubin. Hemolytic anemia and pathological processes occurring in the child’s body prevent sufficient oxygenation and assimilation of nutrients coming from a pregnant woman. As a result, normal development slows down.
- Insufficient nutrition of a woman. Patients who eat low-calorie foods have a monotonous unbalanced diet with a deficiency of proteins, complex carbohydrates, micro- and macroelements, the level of nutrients in the blood decreases. Because of this, plastic processes in the tissues and organs of the fetus slow down, which is accompanied by a delay in development. Often, this reason is the leading one in patients from socially disadvantaged families.
- Adverse external influences. The risk of deterioration of health and the occurrence of disorders in the fetoplacental complex is increased in women who work in industries with vibration, chemical, radiation, thermal loads or live in environmentally unfavorable conditions. Nicotine, alcohol, narcotic substances, some medications (anticonvulsants, ACE inhibitors) have a direct toxic effect.
An additional factor provoking a delay in the normal development of the fetus is a burdened obstetric and gynecological history. The disorder occurs more often in pregnant women with impaired menstrual function, habitual miscarriages or premature birth, infertility in the anamnesis. A lack of nutrients can also be observed in multiple pregnancies due to relative fetoplacental insufficiency.
Prerequisites for the development of the growth retardation syndrome of a child with genetic abnormalities, in the presence of infectious agents, inflammatory processes in the endometrium are laid back in the first trimester of gestation due to violations of trophoblast ingrowth into the membranes of spiral arteries. The disorder of hemodynamics in the uteroplacental system is manifested by a slow blood flow in the arterial bed and the interstitial space. The intensity of gas exchange between the woman and the fetus decreases, which in combination with a violation of the mechanisms of self-regulation of the hyperplastic phase of cell growth leads to a symmetrical variant of developmental delay.
After 20-22 weeks of pregnancy, relative or absolute fetoplacental insufficiency becomes the key moment in the occurrence of fetal hypotrophy. It is during this period that intensive weight gain begins due to active plastic processes. With multiple pregnancies, insufficient nutrition and against the background of diseases accompanied by hypoxemia of the mother’s blood, damage to placental tissue or vascular bed, chronic oxygen starvation of the fetus develops. Its blood flow is redistributed to ensure the full maturation of the central nervous system. The resulting brain-sparin-effect usually becomes the basis of an asymmetric variant of developmental delay.
The systematization of clinical forms of intrauterine growth restriction is based on an assessment of the severity of the lag of fetometric indicators in comparison with the norm and the proportionality of individual growth parameters. The first degree of violations is indicated by a delay in development for 2 weeks, the second — for 3-4 weeks, the third — for more than 4 weeks. An important criterion for assessing the prognosis and the choice of medical tactics is the classification, taking into account the ratio of individual development indicators to each other. On this basis, specialists in the field of obstetrics and gynecology distinguish such forms of fetal hypotrophy as:
- Symmetrical. The circumference of the head, height and weight of the fetus are reduced proportionally in comparison with the average normative indicators for a certain period of pregnancy. It is more often detected in the first or second trimester.
- Asymmetric. Only the size of the baby’s belly has been reduced (for a period of 2 weeks or more). The remaining indicators correspond to the deadline. Usually occurs in the 3rd trimester against the background of signs of fetoplacental insufficiency.
- Mixed. More than a two-week lag from the standard of the size of the abdomen is determined, other indicators are also slightly reduced. Usually, signs of this variant of delay appear at a later date.
The disorder proceeds without acute clinical manifestations and is usually diagnosed with routine ultrasound screening. Fetal hypotrophy can be suspected if a pregnant woman slowly gains weight, her abdominal circumference increases only slightly. Intrauterine growth restriction may be combined with impaired motor activity of the child as a sign of fetoplacental insufficiency. As a result of oxygen starvation, the fetus moves more often and more intensively, and with severe hypoxia, its movements slow down, which serves as an unfavorable prognostic sign.
With fetal hypotrophy, the risk of its stillbirth, injury and birth asphyxia, aspiration of meconium with severe damage to the newborn’s lungs increases. Perinatal disorders are detected in 65% of infants with developmental delay. In the postpartum period, transient hypothyroidism, neonatal hypoglycemia, perinatal polycythemia and high blood viscosity syndrome, hypothermia are more often detected in such children. The functional maturation of the central nervous system may be disrupted with a lag in the formation of tonic and reflex reactions, neurological disorders of varying severity may manifest, intrauterine infections may become more active. According to the results of studies, the long-term consequences of IUGR are an increased risk of insulin-dependent diabetes mellitus and heart disease in adulthood.
The main tasks of the diagnostic stage in case of suspected intrauterine growth restriction are to determine the degree and variant of hypotrophy, assess the state of placental blood flow, identify possible causes of the disease. After a preliminary external obstetric examination with measurement of the circumference of the abdomen and the height of the standing of the uterine fundus of a pregnant woman, it is recommended:
- Ultrasound of the placenta. Sonography allows to determine the degree of maturity of placental tissue, its size, structure, position in the uterus, to identify possible focal lesions. The addition of the method by Dopplerography of the uteroplacental blood flow is aimed at detecting disorders in the vascular bed and areas of infarction.
- Fetometry of the fetus. Ultrasound measurement of the circumferences of the head, abdomen, chest, biparietal and frontal-occipital dimensions, the length of the tubular bones provides objective data on fetal development. The obtained indicators are compared with the normative ones for each gestation period.
- Phonocardiography and fetal cardiotocography. The diagnostic value of the methods consists in an indirect assessment of the adequacy of fetal blood supply by indicators of its cardiac activity. Signs of fetoplacental insufficiency are heart rhythm disorders — arrhythmia, tachycardia.
The combined evaluation of ultrasound and cardiotocographic data makes it possible to compile a biophysical profile of the fetus — to perform a stress test, analyze motor activity, muscle tension (tone), respiratory movements, amniotic fluid volume, placenta maturity. Getting results of 6-7 points indicates a questionable condition of the child, 5-4 points — about severe fetal hypoxia.
Additionally, to determine the causes of the condition, laboratory tests are performed to determine the level of hemoglobin and erythrocytes, the content of hormones (estrogens, chorionic gonadotropin, progesterone, FSH), infectious agents (PCR, RIF, ELISA methods). Possible genetic abnormalities and pathology of the fetal membranes are detected during invasive prenatal diagnostics (amnioscopy, ultrasound-controlled amniocentesis, cordocentesis). The differential diagnosis is carried out with a genetically determined constitutional low weight of the child, prematurity. According to the indications, the pregnant woman is consulted by an endocrinologist, an infectious disease specialist, a therapist, an immunologist, a hematologist.
When choosing medical tactics, the degree of intrauterine hypotrophy of the child, the severity of fetoplacental insufficiency, and the condition of the fetus are taken into account. Treatment is prescribed with mandatory monitoring — ultrasound determination of fetometric parameters every week or every 14 days, dopplerometry of placental blood flow every 3-5 days, assessment of the child’s condition during daily CTG. Pregnant women are shown:
- Drugs that improve fetal blood supply. The quality of blood flow in the uterus-placenta-fetus system increases with the appointment of angioprotectors and agents that affect blood rheology. Additional administration of tocolytics reduces the tone of the uterus, facilitating blood flow in the vessels.
- Antihypoxic and membrane stabilizing agents. The use of actovegin, instenone, antioxidants and membrane stabilizers makes fetal tissues more resistant to hypoxia. When combined with restorative drugs, this allows you to stimulate plastic processes.
With grade I fetal hypotrophy and compensated fetoplacental insufficiency with normal growth rates of fetometric indicators and the functional state of the child, pregnancy is prolonged to at least 37 weeks and confirmation of the maturity of the lung tissue. If the parameters of fetal development could not be stabilized within 2 weeks or the child’s condition worsened (blood flow in the main vessels slowed down, cardiac activity was disrupted), an early delivery is performed regardless of the gestational period. II and III degrees of developmental delay with decompensation of placental insufficiency (pronounced CTG-signs of hypoxia, retrograde blood flow in the umbilical artery or the absence of its diastolic component) is an indication for an early caesarean section.
Prognosis and prevention
With timely diagnosis, proper pregnancy management tactics, the absence of severe diseases of the woman, gross defects and pronounced disorders on the part of the fetus, the prognosis is favorable. The probability of complications increases with an increase in the degree of hypotrophy. To prevent intrauterine growth restriction, it is recommended to plan pregnancy, treat extragenital and genital pathology in advance, sanitize foci of infection, register early in a women’s consultation, regularly visit an obstetrician-gynecologist, follow his recommendations for examination and treatment. Sufficient rest and a night’s sleep, a rational diet, moderate motor activity, and the rejection of bad habits have a positive effect on the development of the child.