🧪 MoM Calculator (Prenatal Screening)
Calculate Multiple of the Median (MoM) for serum and ultrasound markers used in first- and second-trimester aneuploidy and NTD screening.
⚠️ Prenatal Screening Disclaimer
Prenatal screening results must be interpreted by a qualified obstetrician or maternal-fetal medicine specialist. This tool is for reference only; it does not compute individualized risk. Individualized risk requires validated software (PRISCA, FMF, Lifecycle) incorporating maternal age, weight, ethnicity, diabetes status, smoking, IVF, and multiple fetal number. Do not make clinical decisions from a single MoM value.
Prenatal screening results must be interpreted by a qualified obstetrician or maternal-fetal medicine specialist. This tool is for reference only; it does not compute individualized risk. Individualized risk requires validated software (PRISCA, FMF, Lifecycle) incorporating maternal age, weight, ethnicity, diabetes status, smoking, IVF, and multiple fetal number. Do not make clinical decisions from a single MoM value.
Supported: 10–22 weeks
Reference Medians by Gestational Age
Representative literature-based medians. Real medians vary by laboratory and population.
| GA | PAPP-A (mIU/mL) | free β-hCG (ng/mL) | AFP (ng/mL) | NT (mm) |
|---|---|---|---|---|
| 10 wk | 1.2 | 45 | — | — |
| 11 wk | 1.8 | 40 | — | 1.2 |
| 12 wk | 2.6 | 35 | — | 1.4 |
| 13 wk | 3.8 | 30 | — | 1.6 |
| 15 wk | — | — | 25 | — |
| 16 wk | — | — | 30 | — |
| 17 wk | — | — | 35 | — |
| 18 wk | — | — | 42 | — |
Classic MoM Patterns
Trisomy 21 (Down syndrome) pattern
PAPP-A ↓ · free β-hCG ↑ · AFP ↓ · uE3 ↓ · inhibin A ↑ · NT ↑
PAPP-A ↓ · free β-hCG ↑ · AFP ↓ · uE3 ↓ · inhibin A ↑ · NT ↑
Trisomy 18 (Edwards syndrome) pattern
PAPP-A ↓ · free β-hCG ↓ · AFP ↓ · uE3 ↓ · NT ↑
PAPP-A ↓ · free β-hCG ↓ · AFP ↓ · uE3 ↓ · NT ↑
Open neural tube defect (NTD)
AFP ↑↑ (MoM ≥ 2.5)
AFP ↑↑ (MoM ≥ 2.5)
※ No single marker is diagnostic. Risk software combines all markers with maternal factors for individualized risk.
MoM Reference Ranges
| MoM Range | Category | Interpretation |
|---|---|---|
| < 0.4 | Very Low | Significantly low — further evaluation warranted |
| 0.4 – 0.5 | Low | Borderline; interpret with other markers |
| 0.5 – 2.0 | Normal | Typical range for most pregnancies |
| 2.0 – 2.5 | High | Borderline; interpret with other markers |
| > 2.5 | Very High | Significantly high — further evaluation warranted |
Related Calculators
Disclaimer — Educational reference only. Individualized aneuploidy risk requires validated software (PRISCA, FMF, Lifecycle) with adjustment for maternal age, weight, ethnicity, smoking, diabetes, IVF, and multifetal gestation. Reference medians vary significantly by laboratory. Do not clinical decisions from single-marker MoM.
References: Wald NJ et al. J Med Screen. 1997. · Malone FD et al. FASTER Trial. NEJM. 2005. · Fetal Medicine Foundation (FMF) First-Trimester Screening Guidelines 2023.
References: Wald NJ et al. J Med Screen. 1997. · Malone FD et al. FASTER Trial. NEJM. 2005. · Fetal Medicine Foundation (FMF) First-Trimester Screening Guidelines 2023.