Free Beta-hCG MoM Calculator
Free Beta-hCG MoM Calculator
Work out a free β-hCG multiple of the median from your result and your laboratory’s median for the same gestational age, or enter the reported MoM directly, and see what the direction means. The median belongs to your laboratory — this page does not supply one — and a MoM on its own is not a risk: the combined test needs nuchal translucency, PAPP-A and maternal age as well.
Free β-hCG multiple of the median
Result ÷ median → MoMFree β-hCG 88 ng/mL; illustrative median 40 ng/mL
Multiple of the median
- median
- your laboratory’s or programme’s median for that gestational day, on the same assay and in the same unit
- adjusted MoM
- the MoM on a screening report is also corrected for maternal weight, ethnicity, smoking, IVF and diabetes; a simple division is not
- 0.2 and 5
- extremes proposed by one retrospective study (Younesi 2023) — not a guideline threshold
Worked example
Free β-hCG 88 ng/mL; illustrative median 40 ng/mL
88 ÷ 40 = 2.20 MoM
Between 0.2 and 5 MoM, and above the median — the direction seen in trisomy 21
That direction is not a risk: it is one of four inputs to the combined test
The median here is an illustration; with a real laboratory median the answer is only as good as that median
What a free β-hCG MoM can and cannot tell you
| Question | Can a MoM answer it? | Where the answer comes from |
|---|---|---|
| Is free β-hCG high or low for this gestation? | Yes | This page, with your laboratory’s median |
| What is the chance of Down’s, Edwards’ or Patau’s syndrome? | No | The combined test: maternal age, nuchal translucency, free β-hCG and PAPP-A together |
| Is PAPP-A low for growth surveillance? | Not from this marker | The PAPP-A MoM calculator |
| What is the result in another unit? | Not needed for a MoM | The free beta-hCG unit converter |
The direction of the two biochemical markers
| Condition | Free β-hCG | PAPP-A | Source |
|---|---|---|---|
| Trisomy 21 | Raised | Low | Direction only; trisomy 21 more frequent above 5 MoM in Younesi 2023. No median MoM printed here |
| Trisomy 18 | Low (median 0.281 MoM) | Low (median 0.177 MoM) | Tul 1999, 50 cases |
| Trisomy 13 | Low | Not stated here | Direction only: trisomy 13 more frequent below 0.2 MoM in Younesi 2023 |
A ratio to a median that only your laboratory has
Free β-hCG falls through the late first trimester, so a concentration means nothing without the gestational day it was taken on. Screening programmes divide each result by the median for that day in their own population, on their own assay. The answer is a multiple of the median: 1.0 is typical, 2.0 is twice the usual level. That median is specific to the assay, the population and the day, which is why this page will not supply one. Enter the median your laboratory or screening programme uses, in the same unit as the result. This page is the partner of the PAPP-A MoM calculator, and works the same way.
The MoM printed on a screening report has also been adjusted for maternal weight, ethnicity, smoking, IVF conception and diabetes, and a simple division is not, so a MoM calculated here can differ from the reported one. If the report gives a MoM, that is the number to use; enter it with a median of 1.
What the MoM points to is directional. Free β-hCG tends to be raised in trisomy 21 and low in trisomies 18 and 13 — in one series of 50 pregnancies with trisomy 18 the median was 0.281 MoM, with PAPP-A at 0.177 MoM. But the distributions overlap so much with unaffected pregnancies that no free β-hCG value on its own is used to make a decision. The chance of a trisomy comes from the combined test, which puts free β-hCG together with PAPP-A, nuchal translucency and maternal age; a MoM is one input to it, not a result. Cell-free DNA screening, where offered, is more accurate still; see the NIPT positive predictive value calculator.
Outside aneuploidy, no guideline sets a free β-hCG threshold for adverse pregnancy outcome. One retrospective study proposed below 0.2 or above 5 MoM as markers of risk, and the page reports where a result falls against those extremes with that caveat attached. The free beta-hCG unit converter explains why free β-hCG must never be read against a total hCG interval, and the hCG unit converter covers the whole hormone.
Frequently asked questions
How do you calculate a free beta-hCG MoM?
Divide the free β-hCG result by the median for the same gestational day, measured by the same laboratory on the same assay and in the same unit. A result of 88 against a median of 40 is 2.20 MoM. The median must come from your laboratory or screening programme; medians are not transferable between assays or populations.
What does a high free beta-hCG MoM mean?
Raised free β-hCG is the direction seen in trisomy 21, but most high results come from unaffected pregnancies, and a MoM alone is not a risk. The chance of Down’s syndrome comes from the combined test, which also uses PAPP-A, nuchal translucency and maternal age. Wrong dating and twin pregnancies also produce high MoMs.
What does a low free beta-hCG MoM mean?
Low free β-hCG, especially with low PAPP-A, is the pattern of trisomies 18 and 13 — in one series of trisomy 18 the median free β-hCG was 0.281 MoM and PAPP-A 0.177 MoM. As with a high value, it is an input to the combined test, not a result on its own.
Is there a free beta-hCG MoM cut-off for pregnancy complications?
No guideline sets one. A single retrospective study proposed free β-hCG below 0.2 or above 5 MoM as markers of adverse outcome, and this page shows where a result falls against those extremes, labelled as that study’s proposal. Low PAPP-A, by contrast, does have a guideline threshold for growth surveillance: see the PAPP-A MoM calculator.
Why is my calculated MoM different from the one on my report?
Because the reported MoM is adjusted for maternal weight, ethnicity, smoking, IVF conception and diabetes, and a simple division is not. The gestational day and assay also have to match exactly. If your report gives a MoM, use that number.
Related calculators
References
- Tul N, Spencer K, Noble P, Chan C, Nicolaides K. Screening for trisomy 18 by fetal nuchal translucency and maternal serum free beta-hCG and PAPP-A at 10–14 weeks of gestation. Prenat Diagn. 1999;19(11):1035–1042. — in 50 cases of trisomy 18, median free β-hCG 0.281 MoM and PAPP-A 0.177 MoM.
- Younesi S, Eslamian L, Khalafi N, et al. Extreme βHCG levels in first trimester screening are risk factors for adverse maternal and fetal outcomes. Sci Rep. 2023;13:1228. — a single retrospective study proposing free β-hCG below 0.2 MoM or above 5 MoM as risk markers; not a guideline threshold.
- Roche Diagnostics. Elecsys free βhCG method sheet — medians by completed gestational week, standardised against NIBSC 75/551; medians are assay-specific.
- Royal College of Obstetricians and Gynaecologists. The Investigation and Management of the Small-for-Gestational-Age Fetus. Green-top Guideline No. 31, 2013 — the PAPP-A (not free β-hCG) threshold of 0.415 MoM, cited for contrast.
Medical Disclaimer: The tools and content provided here are for educational and reference purposes only. They are not intended to substitute for professional medical advice, diagnosis, or treatment. Clinical decisions should always be based on the comprehensive assessment of a qualified healthcare professional.