MCA Calculator

MCA Calculator

The MCA calculator assists in determining the potential risk of fetal anemia in pregnancies. It measures the middle cerebral artery during a prenatal doppler scan to check for fetal anemia risk.

This article will discuss the MCA calculator,  the middle cerebral artery doppler during pregnancy, and how it is used to detect fetal anemia.

What is the MCA calculator?

The MCA calculator evaluates fetal anemia risk in singleton and twin pregnancies. The calculations are based on an MCA doppler scan, typically done during prenatal checkups.

The calculator will show you the median MCA velocity at a particular gestational age, the Multiple of Median (MoM) value, and its full definition.

You may also be interested in this detailed article on Pregnancy glucose test.

What is MCA?

The “Middle Cerebral Artery,” or MCA, is one of the three largest blood arteries feeding the brain; it is apparent during fetal ultrasounds. Its measurements are used to evaluate the child’s health.

The MCA evaluation is used in the following ways:

  • Screening for and evaluating pre-eclampsia risk
  • When Rh+/Rh- serological conflict is suspected.
  • A growth restriction diagnosis.
  • Issues in multiple pregnancies.

All of these conditions lead to hypoxia or an insufficient amount of oxygen reaching the fetus’s body. The brain, heart, and lungs, three of the fetus’s most vital organs, are among those that the body is attempting to safeguard. In order to have the optimum blood supply for these organs, the infant reroutes blood flow in that direction. All of these cause the arteries in the brain to swell, and the blood flow through them accelerates.

In severe cases, the blood flow is so slight that it is impossible to see any evidence of blood flow inside the brain’s blood arteries since the flow seen during diastole is retrograde. This condition is extremely dangerous and demands prompt medical care.

Because of the lower blood viscosity and high cardiac output linked to anemia, the MCA PSV in fetuses with anemia seems to rise over the usual range.

Single measurements of the MCA PSV blood flow have been shown to have a 100% sensitivity and a 12% false positive rate in predicting the existence of moderate or severe anemia in fetuses, with the false positive rate increasing after 35 weeks of gestation.

The MCA PSV can be used to assess fetal anemia brought on by:

  • red blood cell alloimmunization,
  • Twin-to-twin transfusion,
  • twin anemia-polycythemia sequence,
  • Alpha-thalassemia, parvovirus,
  • Fetomaternal hemorrhage,
  • G6PD deficiency,
  • placental chorioangioma, and other potential causes.

Since the peak systolic velocity (PSV) of the middle cerebral artery (MCA) typically rises with gestational age, it is critical that the gestational age be precisely determined.

You may also like to see this easy way to remember heart block as the heart block poem.

What are MCA dopplers in ultrasound?

MCA Dopplers is an ultrasound that measures the rate at which blood moves through a baby’s brain. The reading must be obtained at the proper angle.

After converting to an MoM (multiples of the median or average for your kids’ gestational age), the resultant measurement is in centimeters per second.

Anemia is indicated by excessively rapid blood flow, whereas polycythemia is indicated by languid blood flow. TAPS (Twin Anaemia polycythemia Sequence) is identified when one twin is polycythemic and the other is anemic.

In complicated pregnancies, such as those with intrauterine growth retardation and fetal anemia, doppler measurements in the Middle Cerebral Artery (MCA) are a component of the assessment of the fetus’ well-being.

How to use MCA Calculator

The following information is necessary to utilize the MCA calculator fully:

  • Pregnancy age., in weeks.
  • MCA peak systolic velocity. This is assessed throughout a typical prenatal checkup—an ultrasound readout of the fetal middle cerebral artery.

How to calculate MCA

Based on gestational age (weeks 18 to 40), there are defined values for the median peak systolic velocity that can be found in published tables or calculated by:

Middle Cerebral Artery Peak Systolic Velocity (MCA-PSV) = e (2.31 + 0.046 GA). GA = Gestation age in weeks.

With the following characteristics: R2=0.78, P<0.001.

When the median MCA-PSV is compared to the observed MCA during Doppler ultrasound, the Multiple of the Mean (MoM) is calculated, which is a measure of how the measured MCA differs from the median population MCA.

Multiple of the Median (MoM) = Doppler MCA PSV / MoM 1 (Median).

With every 100g (3.5 ounces) of fetal weight gain, the MCA peak systolic velocity increases by 0.2 cm/s.

The risk of fetal anemia is greatest when measured peak systolic velocities are 1.5 times or greater than the median.

For a precise measurement during the Doppler:

  • The fetus needs to be still and not breathing or moving at all.
  • The MCA must take up at least half of the enlarged image.
  • The direction of the blood flow should be parallel to the ultrasound beam.
  • The blood flow direction should be parallel to the ultrasonic beam. The ultrasonic beam’s angle concerning the direction of blood flow should be zero degrees.
  • A 2 mm sample of the MCA must be taken from the internal carotid artery.
  • Measure the highest peak systolic velocity.
  • At least three measurements are taken.


Middle cerebral arterial fetal (MCA) Doppler evaluation is crucial in determining whether a fetus is in hypoxia, anemia, or cardiovascular distress. In singleton and twin pregnancies, the MCA calculator helps identify the possible risk of fetal anemia. Early MCA detection is essential for the health of babies.


In a pregnancy, what is a typical MCA PI?

Brain-sparing is deemed to be present when values fall below the fifth percentile. An MCA/umbilical artery PI ratio of less than 1.08 is seen as evidence of redistribution of fetal circulation or brain-sparing.

How does MCA flow in pregnancy work?

An essential step in determining fetal cardiovascular distress, fetal anemia, or fetal hypoxia is the fetal middle cerebral arterial (MCA) Doppler examination. It is a beneficial addition to umbilical artery Doppler examination in the appropriate circumstance.

What is an MCA diagnosis?

When blood flow from the most prominent artery in the brain is abruptly halted (ischemia) or completely stopped, a middle cerebral artery (MCA) stroke ensues (infarction ). Blood supply is cut off, which results in tissue death and severe, possibly irreversible brain damage.

Back to top button