Normal Values for the Fetal Middle Cerebral Artery

After the egg and sperm fuse to form a zygote, cell division begins—some cells differentiate into the brain, while others develop into the nervous system. So, what are the normal values for the fetal middle cerebral artery (MCA)?

Normal Values for the Fetal Middle Cerebral Artery

The normal pulsatility index (PI) range for the fetal middle cerebral artery varies with gestational age. At 30–32 weeks’ gestation, the normal PI range is 1.89 ± 0.62; at 33–35 weeks, it remains 1.89 ± 0.62; at 36–38 weeks, the normal PI range is 1.57 ± 0.50; and at 39–41 weeks, it is 1.41 ± 0.48. The PI of the fetal middle cerebral artery is one of the key indicators used to assess whether intrauterine hypoxia is present in the fetus.

In addition to measuring the MCA-PI, clinical evaluation should integrate maternal medical conditions and fetal movement patterns to determine whether intrauterine hypoxia has occurred. If the mother exhibits significantly elevated blood pressure or blood glucose levels, has pregnancy-related complications, and shows abnormal MCA-PI values, fetal hypoxia should be strongly suspected. Furthermore, fetal heart rate monitoring can also help assess fetal oxygenation status.

Late decelerations or variable decelerations observed on fetal heart rate monitoring during late pregnancy—especially when accompanied by abnormal MCA-PI—suggest fetal hypoxia. We hope this information is helpful to you!