Fetal macrosomia is a child with an intrauterine weight of more than 9 lb. Children who have a birth weight of over 5 kg are called gigantic. Pregnancy with a fetal macrosomia is manifested by a significant increase in the circumference of the abdomen and the weight of the pregnant woman, high standing of the uterine floor. To deliver the diagnosis, fetometry is used, which, according to indications, is supplemented with the determination of blood sugar levels, a glucose tolerance test, and invasive methods of prenatal diagnosis. During the management of pregnancy, monitoring of the condition of the woman and fetus is provided. The natural or operative delivery option is selected taking into account the data obtained during the examination.
Fetal macrosomia is spoken of in cases when its weight is greater than the 90th percentile, which corresponds to the gestational age. The growth of large and giant children is increased by more than 54 cm, their body proportions are normal, there are no signs of genetic abnormalities and intrauterine damage to organs and systems. To date, the frequency of carrying children with a large weight is 8.8-10.5%. Giant babies are born in every 3,000 births. Newborn macrosomia is more often observed in women who have repeatedly given birth over the age of 30, patients with signs of obesity and diabetes mellitus. According to statistics, 28.5% of pregnant women with the 1st degree of obesity have a large baby. At the 2nd degree, this indicator reaches 32.9%, and at the 3rd – 35.5%. Since the birth of a fetal macrosomia increases the likelihood of complications, such children require more careful medical supervision.
The growth and weight of an intrauterine child increase proportionally in the presence of one or a combination of several provoking factors related to the state of health, the nutritional behavior of the expectant mother, the peculiarities of the course of present and past pregnancies. According to research in the field of obstetrics and gynecology, the most common causes of the birth of large children are:
- Metabolic disorders in a pregnant woman. Fetal macrosomia is more often detected in women with insulin-independent, insulin-dependent, gestational diabetes, obesity. Violation of carbohydrate and fat metabolism contributes to the acceleration of plastic processes in the child’s body due to the anabolic effect of insulin.
- Irrational diet. A rapid increase in fetal weight is noted with a high average daily caloric intake and a disturbed ratio between the main nutritional ingredients. The risk of macrosomia increases with excessive consumption of fats and carbohydrates, lack of calcium, phosphorus, copper, vitamins B1, B2, C, PP.
- Postponement of pregnancy. The prolongation of the gestational period is accompanied by the continuation of intrauterine fetal development, further increase in its weight and growth. This factor is of particular importance for women who have given birth many times, since each subsequent pregnancy is often longer than the previous one.
- Genetic predisposition. The role of hereditary mechanisms in the occurrence of macrosomia is still being studied. In favor of the genetic theory, the frequent birth of large children from strongly built tall parents testifies. Specialists reasonably include women in the risk group with a height of 1.70 m and a body weight of 70 kg.
- A large newborn in a previous pregnancy. According to statistics, the weight of the second fetus is often 20-30% more than the first. Most likely, this is due to the higher readiness of the woman’s body for gestation and the better functioning of the placental system. In addition, endocrinopathies and somatic diseases worsen with age.
- The use of drugs with an anabolic effect. More intensive growth of the child’s tissues occurs when taking certain medications that enhance anabolism. Hormonal drugs (glucocorticoids, progestogens), inosine, glucose, orotic acid and a number of other substances have a similar effect.
The main mechanism leading to the development of a fetal macrosomia is the acceleration of plastic processes. Usually, a significant weight gain is associated with the intake of more nutrients through the placenta with a high-calorie diet and exposure to high concentrations of insulin produced in response to excess glucose in the blood of a pregnant woman. The intensification of anabolic processes is manifested by an increase in the formation of fetal tissues, an increase in its size. The ability to grow and develop rapidly due to the active assimilation of nutrients can also be constitutionally conditioned. Prolonging the gestation period aggravates the situation, since the capabilities of the aging placenta cease to meet the needs of a large-sized fetus in nutrition and oxygen.
Usually, the course of pregnancy when carrying a large child practically does not differ from the physiological one. Possible signs of large fetal sizes by the time of delivery are a woman’s weight gain of more than 15 kg, abdominal circumference of 100 cm or more, the height of the uterine fundus above 42 cm. 7-10% of women complain characteristic of compression of the enlarged uterus of the inferior vena cava. In the supine position, they note a significant deterioration in well—being – dizziness, weakness, nausea, ringing in the ears, chest heaviness, darkening in the eyes. Closer to childbirth, the severity of such disorders can reach the depth of the fainting state. Typical disorders of the gastrointestinal tract — a feeling of heartburn after eating and constipation.
Fetal macrosomia exerting increased pressure on the isthmic-cervical region is one of the factors of the formation of a short cervix and a high risk of early termination of pregnancy. By the end of gestation, fetoplacental insufficiency and hypoxia may occur due to the discrepancy between the functional capabilities of the placenta and the needs of the child. Childbirth is complicated by premature outpouring of amniotic fluid, prolonged flow, weakness of labor activity, fetal asphyxia. The risk of maternal injury is higher — ruptures of the perineum, vagina, cervix and uterus body, divergence of the pubic symphysis. Birth injuries of a newborn are possible — fractures of the bones of the handle, collarbone, the formation of cephalohematoma, damage to the brachial nerve plexus, hemorrhages in the brain. After childbirth, hypotonic uterine bleeding occurs more often.
In large children carried by women with diabetes mellitus, polycythemia, respiratory distress syndrome and metabolic disorders – hypoglycemia, neonatal hypocalcemia, hypomagnesemia, hyperbilirubinemia — are likely immediately after childbirth. The long-term consequences of complicated childbirth by a fetal macrosomia are the formation of rectal-vaginal and genitourinary fistulas as a result of prolonged compression of the soft tissues of the birth canal with a clinically narrow pelvis, paresis of the leg muscles with lameness. Children who have suffered birth trauma may have neurological disorders and lag behind in psychomotor development. According to the results of observations, in women who have given birth to a child weighing from 3740 g, the risk of breast cancer in the future increases by 2.5 times, which is associated with a specific hormonal restructuring of the body — an increase in the concentration of estrogens, a decrease in the level of antiestrogens and the release of significant amounts of insulin-like growth factor.
A significant increase in the weight and volume of the pregnant woman’s abdomen is the basis for the appointment of examination methods that allow determining the large size of the fetus. The objectives of the diagnostic search are to evaluate fetometric indicators and vital activity of the child, to exclude other disorders in which similar clinical manifestations are noted. If a fetal macrosomia is suspected , it is recommended:
- Fetometry of the fetus. Based on the data on the biparietal size of the head, the circumference of the child’s abdomen, the length of the femur and its ratio to the girth of the abdomen, it is possible to calculate the estimated body weight fairly accurately. Ultrasound also provides information about the amount of amniotic fluid, identifies multiple pregnancies and possible anatomical defects.
- Determination of blood sugar level. Since large children are often born in pregnant women with hyperglycemia, glucose analysis allows us to clarify the cause of fetal hypertrophy. The indicator is a marker for the proper management of pregnancy. To diagnose latent diabetes mellitus, the examination is supplemented with a glucose-tolerant test.
- Invasive diagnostic methods. They are indicated for suspected genetic defects and developmental abnormalities, which are manifested by pathological fetal macrosomia. To confirm chromosomal pathology, taking into account the term, amniocentesis under ultrasound control, placentocentesis, cordocentesis are used. The latter method is also effective for determining Rh-conflict.
After the 30th week of pregnancy, cardiotocography or phonocardiography of the fetus, dopplerography of the uterine-placental blood flow are performed to assess the condition of the child and timely detection of fetoplacental insufficiency according to indications. When signs of a threat of termination of pregnancy appear, cervicometry is performed to exclude isthmic-cervical insufficiency. The condition is differentiated with multiple pregnancy, polyhydramnios, hereditary macrosomias (Beckwith-Wiedeman, Marshall, Sotos, Weaver syndromes), edematous hemolytic disease, other fetal diseases (hydrocephalus, teratoma, erythroblastosis, etc.), submucosal and subserous uterine fibroids. If necessary, the patient is consulted by an endocrinologist, a geneticist, an immunologist.
Management of pregnancy and childbirth
The tactics of pregnancy management with a large mass of the child involves regular monitoring of the condition of the mother and fetus. Drug therapy with the appointment of antispasmodics and tocolytics is indicated only at the risk of premature birth. If the disorder is combined with shortening of the cervix, it is possible to install an obstetric pessary or suture around the cervical canal. The patient is recommended therapeutic gymnastics, correction of the diet with a restriction of the amount of carbohydrates and fats. In the treatment of concomitant diseases and complications of pregnancy, it is necessary to exclude drugs with an anabolic effect.
Usually a fetal macrosomia is able to be born on its own, but in some cases a caesarean section is preferable. The optimal method of delivery is chosen taking into account data on past pregnancies and childbirth, information on the clinical correspondence of the size of the fetus and the pelvis of a woman, the presence of extragenital and genital pathology, the timing and features of the gestational period:
- Operative delivery. Caesarean section is indicated for post-term pregnancy, pelvic presentation, anatomical narrowing of the pelvis, the presence of myomatous nodes or abnormalities of the uterus. Surgical intervention is also performed for women in labor under the age of 18 and from 30 years with diseases in which it is necessary to reduce or eliminate the labor period, stillbirth and habitual miscarriage in the past, conception with the help of ART.
- Natural childbirth. Recommended for uncomplicated pregnancy, favorable obstetric history and sufficient pelvic size for the passage of the child through the birth canal. During childbirth, the contractile activity of the uterus and the condition of the fetus are necessarily monitored, the correspondence of the head to the size of the pelvis is monitored. If necessary, analgesics, antispasmodics, uterotonics are introduced. In the subsequent and early postpartum period, measures are taken to prevent postpartum bleeding.
If weakness and other abnormal labor are observed in natural childbirth, signs of fetal hypoxia occur, diagnostic criteria for functional narrowing of the pelvis are determined, delivery is completed by emergency caesarean section for vital indications. Intranatal fetal death in complicated labor serves as an indication for craniotomy.
Prognosis and prevention
Timely diagnosis and the correct choice of delivery method minimize possible complications and negative consequences of carrying a fetal macrosomia. For preventive purposes, women suffering from obesity, diabetes mellitus are recommended to plan pregnancy with weight loss and treatment of the underlying disease. Pregnant patients from the risk group are shown early registration in consultations, regular examinations by an obstetrician-gynecologist, scheduled ultrasound screening, sufficient motor activity, a rational diet with a high protein content, restriction of foods rich in carbohydrates and fats.