MicroSort
Last reviewed 2026-10-27
MicroSort is a flow-cytometry technique for enriching a sperm sample for X- or Y-bearing sperm, and it is no longer generally available in the United States. Its US clinical trial did not complete to approval, and the technology has since been offered through licensed laboratories abroad. It shifts the odds; it does not choose. The enrichment figures you will see quoted come principally from the programme itself rather than from independent replication.
What it actually does
An X chromosome carries measurably more DNA than a Y chromosome — a difference of a few per cent in total sperm DNA content. MicroSort stains sperm with a DNA-binding fluorescent dye and passes them single-file through a flow cytometer. X-bearing sperm fluoresce slightly more brightly, and the instrument deflects them into a separate collection stream. The enriched sample is then used for IUI or IVF.
The physics is sound. The questions that have always surrounded it are different ones: how much of the laboratory enrichment translates into the sex ratio of actual births, and what the dye and the laser do to sperm that are subsequently used to make a child.
Why Americans cannot get it
MicroSort was developed from US Department of Agriculture livestock-sorting work and ran under an FDA clinical trial in humans. That trial did not complete to marketing approval, and the service stopped being offered in the United States. What remains is the technology operating through licensed laboratories in other countries. This is the single most common point of confusion: people search for MicroSort, find pages describing it in the present tense, and do not realise those pages describe a service in another jurisdiction.
The accuracy figures, and where they come from
Published figures report higher enrichment for X (female) sorting than for Y (male) sorting — the DNA difference the instrument measures is easier to resolve in one direction than the other. The important qualification is the provenance: the substantial datasets in this field were generated by the programme operating the technology, as part of its own trial reporting. That does not make them false. It does mean that independent replication is thin, and a figure repeated across fifty clinic websites is still one source.
Treat any “up to X% accurate” claim for sperm sorting as a laboratory enrichment figure, not a probability of a child of that sex. Between the sorted sample and a birth sit fertilisation, implantation and a pregnancy — and no sorting method removes the possibility of the other sex.
MicroSort versus embryo testing
| MicroSort / sperm sorting | PGT-A during IVF | |
|---|---|---|
| What you get | A sample enriched for one sex | The sex of each embryo, identified |
| Certainty | A tilt in the odds | A definite answer for the embryo transferred |
| Requires IVF | No — can be used with IUI | Yes |
| Cost | Lower per attempt | Higher per cycle |
| Evidence | Operator-reported, limited independent replication | Routine, well-established laboratory practice |
| Honest summary | Cheaper, and you may well get the other sex | Expensive, and the uncertainty moves to whether you make an embryo of that sex |
The choice between them is not really cost against accuracy. It is a tilt you can afford against an answer you might not be able to — and for most people the deciding question is how they would feel about a child of the other sex, which is worth answering before spending anything.
Does MicroSort still exist?
Not as a generally available service in the United States; its US clinical trial did not complete to approval. The technology has been offered through licensed laboratories in other countries.
How accurate is MicroSort?
Reported enrichment is higher for female than for male sorting, but the substantial datasets were produced by the programme operating the technology. Independent replication is limited, and an enrichment figure is not a probability of a child of that sex.
Is MicroSort better than PGT-A for choosing gender?
No. Sperm sorting shifts the odds; embryo testing identifies the sex of each embryo. If you want an answer rather than a tilt, PGT-A during IVF is the only route.
Can I use MicroSort with IUI?
Yes, and it is commonly sold that way as the affordable option. You then inherit both limitations: partial enrichment and the modest pregnancy rate per IUI cycle.
Sources
- Karabinus DS, Flow cytometric sorting of human sperm: MicroSort clinical trial update, Theriogenology, 2009 — the principal operator-reported dataset
- US Food and Drug Administration — device and clinical-trial regulation — link
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