Microblood testing is a type of blood gas analysis that can take place on the fetus during delivery. Blood gas analysis is done primarily in the absence of a clear cardiotocogram and is intended to rule out cerebral damage to the fetus during birth. For example, the microblood test may indicate [[acidosis]] and thus prompt obstetricians to terminate the delivery as soon as possible.
What is microblood testing?
Microblood testing is a blood gas analysis that takes place on a fetus. The procedure is used during ongoing birth. Blood gas analyses are in diagnostic procedures to determine blood gas distribution. With a blood gas analysis, statements can be made about oxygen and carbon dioxide, as well as those about the pH and acid-base balance in the blood. Micro blood analysis is a blood gas analysis that takes place on a fetus. The procedure is used during ongoing delivery when cardiotocography does not provide clarity. Cardiotocography is a standard procedure for monitoring and recording cardiac activity in fetuses. At the same time, maternal labor activity is recorded. Obstetricians use the procedure especially in late pregnancy and immediately at the birth of the baby. Lack of clarity in the cardiotocogram can endanger the life of the fetus. If there is a suspicion of inadequate oxygenation of the infant during delivery or if the infant’s heart rate is on the verge of pathological values, the microblood examination can provide unambiguity. Obstetricians can gather valuable information to plan further procedures and assess the need for intervention. Meanwhile, because of its low risks to the fetus, microblood testing is one of the standardized and frequently used procedures during labor.
Function, effect, and goals
Hypoxemia during birth can cause severe damage to the fetus’s organism, leading to its death in extreme cases. Microblood testing can be used to assess the risk for such an event. Microblood examination is used mainly in cases of suspected but not clearly pathological findings in cardiotocography and verifies the findings of cardiotocogram. The indication for blood gas analysis arises, for example, in the case of labor-synchronous values above 30 percent DIP I during the opening phase of a birth. Other indications may include mild or moderate DIP II at the end of labor or variable moderate decelerations and decelerations. In the latter indication, unfavorable additional criteria are usually present and associated with a poor prognosis for the child. Lack of clarity about fetal bradycardia or tachycardia may also be an indication for blood gas analysis in terms of microblood examination, so especially inform a heart rate below 110 or above 150. The scalp of the fetus is disinfected to perform microblood examination with the aid of amnioscopic view or speculum setting. Disinfection is followed by hyperemization with liquid nitrogen. Subsequently, the scalp prepared in this way is incised and then releases capillary blood. The fetal blood is placed in heparinized glass capillaries and analyzed for blood gas levels using the Astrup method. The analysis is followed by the evaluation of the values. The pH value is particularly significant in this context. According to Saling, a pH value below 7.20 indicates acidosis and thus a disturbance of the acid-base balance. pH values above 7.30 are considered normal. Values between 7.29 and 7.25 are reduced and values between 7.24 and 7.20 are considered preacidosis. From 7.19 to 7.15, mild acidosis is present. The degree increases to moderate acidosis with values between 7.14 and 7.10 and to advanced acidosis with values between 7.09 and 7.05. Severe acidosis is present with ph values below 7.04. With acidosis, the risk of cerebral damage to the fetus may open up. However, this is only true for severe acidosis that persists for an extended period of time. If the values are normal or merely preacidotic, obstetricians repeat the microblood test at thirty-minute intervals. Falling pH values indicate that the birth will be terminated as soon as possible, for example by cesarean section.
Risks, side effects and dangers
There are some risks to the fetus with microblood testing. Blood is drawn from a puncture site on the scalp. This puncture site can begin to bleed profusely if not performed properly. Such bleeding puts additional stress on the fetus. If he is already in a health-threatening situation and is correspondingly weakened, any bleeding that occurs can, in extreme cases, worsen his condition even further. However, since the puncture site for blood collection is extremely limited in size when performed properly, the risk of bleeding is rather negligible. The same applies to the possible risk of infection associated with the puncture site. Only in absolutely exceptional cases are microblood tests associated with complications. For the obstetricians of a hospital, the procedures are usually part of the everyday standard. Improper performance and the resulting bleeding or infection of the puncture site are therefore normally virtually ruled out. The risk-benefit ratio makes microblood analysis a frequently used procedure. Indeed, without blood gas analysis, cardiotocograms lacking unambiguity carry the far more serious risk of fetal cerebral damage, which in extreme cases can even lead to death. Microblood testing can prevent this emergency by providing obstetricians and physicians with clear information and prompting them to intervene as necessary. Often, based on the values, a saving cesarean section is initiated.