Diagnosis and monitoring of the fetus
Modern medicine makes it possible to determine the child's Rhesus factor even before birth. This is done by examining fetal erythrocytes in the mother's peripheral blood. This non-invasive method has 100% accuracy and helps avoid unnecessary invasive procedures if the fetus turns out to be Rhesus-negative.
If the child is Rhesus-positive, the management tactics depend on their condition:
- Normal values: if hemoglobin (Hb) and hematocrit (Ht) correspond to the gestational norm, a repeat cordocentesis is scheduled in 4 weeks (or earlier if ultrasound signs of pathology appear).
- Signs of the disease: a drop in Hb and Ht by 15% or more serves as a direct indication for initiating intrauterine treatment.
Cardiotocography (CTG) is mandatory to assess the severity of hypoxia. The more severe the condition, the more pronounced the changes on the tracing. The appearance of a sinusoidal curve type is a ominous specific symptom indicating the development of the hydropic form and an extremely severe condition of the child. When signs of hypoxia are present, CTG is performed daily.
The comprehensive management plan for a patient with Rhesus sensitization is also based on data from ultrasound fetometry and placentometry, as well as the results of amniocentesis and cordocentesis. Doppler assessment plays an important role — specifically, measuring the peak systolic velocity in the fetal middle cerebral artery (MCA PSV), which is performed at intervals of 1–3 days. The final tactics depend on the gestational age, the condition of the fetus, and the level of equipment in the perinatal center (availability of resuscitation and blood transfusion capabilities).
Intrauterine blood transfusion
The main treatment method for severe forms of hemolytic disease of the fetus is intrauterine intravascular blood transfusion. The procedure helps increase hemoglobin levels, maintain hematocrit above critical levels, prevent the development of hydrops, and safely prolong pregnancy.
Execution Technique:
- Cordocentesis is performed to collect blood and assess the pre-transfusion hematocrit.
- The transfusion volume is calculated taking into account the fetal Ht, donor blood Ht, and gestational age.
- A blood product is administered — washed O(I) Rhesus-negative red blood cells, depleted of leukocytes and platelets.
- The administration rate is strictly controlled and should not exceed 1 ml/min.
- Upon completion, a control analysis is taken to assess post-transfusion blood parameters.
Transfusion of Rhesus-negative red blood cells reduces the relative proportion of Rhesus-positive cells in the fetal circulation, thereby dampening the maternal immune response. The need for repeated procedures depends on the gestational age and the hematocrit level after the procedure. Transfusions can be repeated up to the 32nd week of pregnancy, after which the issue of premature delivery is raised.
Choice of delivery method
The management of labor in Rhesus sensitization is based on gestational age, the child's condition, parity, and the readiness of the birth canal.
- Vaginal delivery: is permitted if the gestational age exceeds 36 weeks, the cervix is ripe, and there are no clinical signs of a severe form of the disease.
- Cesarean section: is the preferred method in severe cases of the pathology. The surgery is performed regardless of gestational age to exclude additional trauma to the sick fetus during passage through the birth canal.
Diagnosis and clinical forms after birth
Immediately after birth, blood must be tested from the umbilical cord of a baby born to a Rhesus-negative or sensitized mother.
The mandatory range of umbilical cord blood tests includes:
- Determination of blood group and Rhesus affiliation.
- Measurement of hemoglobin level.
- Determination of bilirubin level.
- Performing a direct Coombs test (direct antiglobulin test).
In the early neonatal period, three main clinical forms of the disease are distinguished:
- Hemolytic anemia without jaundice and hydrops.
- Hemolytic anemia with jaundice.
- Hemolytic anemia with jaundice and hydrops (the most severe form).
To memorize the three forms of HDFN in order of increasing severity, use the rule "A-J-H": Anemia → Jaundice develops → Hydrops develops.
Class and exam questions
What to do if non-invasive diagnostics reveal that the fetus is Rhesus-negative?
In this case, the risk of developing hemolytic disease is absent. The pregnant woman continues to be monitored according to the standard protocol as a non-immunized patient.
Why is it necessary to transfuse specifically Rhesus-negative blood to the fetus?
Administration of Rhesus-negative red blood cells reduces the relative number of Rhesus-positive cells in the fetal blood. This helps weaken the immune response of the maternal organism.
How often should CTG be performed in hemolytic disease?
If the fetus already shows signs of hypoxia, cardiotocographic monitoring must be performed daily.
What else to study on this topic
- Ultrasonic fetometry and placentometry in Rhesus conflict
- Assessment of peak systolic velocity in the middle cerebral artery (MCA PSV)
- Indications and technique for amniocentesis and cordocentesis
- Organization of perinatal care for nursing premature infants with HDFN
- Interpretation of direct Coombs test results
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