Multiple of the median

Multiple of the Median (MoM) is a statistical measure used primarily in the field of medicine, particularly in the screening and diagnosis of various conditions during pregnancy. It is a way to standardize a measurement, such as the level of a particular hormone in the blood, by comparing it to a median value expected at a certain point in pregnancy. This allows healthcare providers to assess whether the levels are normal, elevated, or decreased, which can be indicative of potential health issues in the fetus or the pregnant individual.

Definition

The Multiple of the Median (MoM) is calculated by dividing the individual's test result by the median value of the reference population for the same gestational age. A MoM value of 1 indicates that the measurement is exactly at the median of the reference population. Values above or below 1 indicate measurements that are higher or lower than the median, respectively.

Application in Prenatal Screening

MoM is extensively used in prenatal screening tests to assess the risk of chromosomal abnormalities such as Down syndrome (Trisomy 21), Edwards syndrome (Trisomy 18), and Patau syndrome (Trisomy 13). It is also applied in the screening for neural tube defects.

First Trimester

In the first trimester, MoM values of certain biomarkers in the mother's blood, such as free beta-human chorionic gonadotropin (β-hCG) and pregnancy-associated plasma protein A (PAPP-A), are analyzed. Abnormal MoM values can indicate an increased risk of chromosomal abnormalities.

Second Trimester

During the second trimester, the quad screen measures the MoM values of four different substances in the maternal blood: alpha-fetoprotein (AFP), unconjugated estriol (uE3), inhibin A, and β-hCG. These values help in assessing the risk of chromosomal abnormalities and neural tube defects.

Advantages and Limitations

The use of MoM allows for a more personalized assessment of risk, taking into account individual variations and the specific week of pregnancy. However, it is important to note that MoM values are part of a screening process and not a definitive diagnosis. Abnormal MoM values warrant further diagnostic testing, such as amniocentesis or chorionic villus sampling (CVS), to confirm any findings.

Conclusion

Multiple of the Median is a crucial concept in the field of prenatal screening, providing a standardized method to interpret various biomarkers. It plays a significant role in the early detection of potential health issues, thereby facilitating timely interventions and informed decision-making during pregnancy.