[Feto-maternal hemorrhage: Guidelines of the French College of Obstetricians and Gynecologists. Expert consensus from...

The objective is to determine the circumstances in which feto-maternal hemorrhage (FMH) should be investigated, and how to assess its volume and whether it is acute or chronic, in order to build guidelines for appropriate management.

The French College of Obstetricians and Gynecologists (CNGOF) conducted a formalized expert consensus method.

Feto-maternal hemorrhage (FMH) is defined as the passage of fetal blood into the maternal circulation through a breach in the feto-placental barrier during pregnancy or childbirth. For the diagnosis of FMH, it is recommended that a Kleihauer-Betke (KB) test be performed as a first-line test, with a positivity threshold of 5 fetal red blood cells per 10,000 adult red blood cells. The volume of fetal blood lost in mL is calculated by dividing the TB test result by 2. Flow cytometry can also be used as a supplement in specialized laboratories if the TB test is difficult to interpret. In the context of FMH, to screen for fetal anemia, it is suggested to perform an ultrasound scan with measurement of the peak systolic velocity in the middle cerebral artery and, depending on the gestational age, to monitor the fetal heart rate. Normal results from these tests do not rule out the presence of fetal anemia. It is suggested that a KB test be performed in cases of decreased fetal movement with abnormal initial assessment, ultrasound signs of fetal anemia, sinusoidal fetal heart rate, or fetal death, in order to detect FMH. It is suggested that a KB test not be performed routinely in cases of ovular sampling, external version or bleeding during pregnancy. In cases of abdominal trauma, it is suggested that a KB test be performed, depending on the characteristics of the shock (high intensity, direct abdominal trauma). In cases of FMH, it is suggested that the severity be assessed based on the estimated volume transfused, the presence or absence of ultrasound signs of fetal anemia, and the presence or absence of fetal heart rate abnormalities. To estimate the volume of transfused blood, it is suggested to use the KB test, the result of which will be related to the estimated fetal weight based on ultrasound measurements. The medical care and follow-up will then depend on the level of risk. In cases where there is a history of FMH in a previous pregnancy, it is suggested to reassure the patient about the risk of FMH recurrence and not to perform any specific monitoring during a subsequent pregnancy.