Products of Conception (POC) Genetic Testing

"Products of conception" is the medical term for the tissue that develops in early pregnancy — the developing baby and the placenta. Products of conception genetic testing analyses this tissue after a miscarriage to look at its chromosomes, the tightly packed structures inside each cell that carry our genes.

The test looks for a chromosomal abnormality — too many chromosomes, too few, or chromosomes that are structurally altered. This is the single most common reason an early miscarriage happens. Knowing whether a chromosomal problem was involved can bring some understanding at a very difficult time.

At London Pregnancy Clinic we do not process the tissue in our own laboratory. Instead, we provide the genetic counselling around the test, arrange the analysis through our accredited genetics partners, and support you in understanding what the results mean for you.

Miscarriage is far more common than many people realise, and about half of early miscarriages are linked to a chromosomal abnormality in the developing baby that has simply happened by chance.

After a single early loss, routine testing is not usually recommended. In the UK, the Royal College of Obstetricians and Gynaecologists' 2023 recurrent miscarriage guideline recommends offering chromosome testing of the pregnancy tissue from the third miscarriage onwards, and after any miscarriage in the second trimester. Doctors may begin other investigations after two miscarriages if they suspect an underlying cause.

Privately, tissue testing can be arranged after any miscarriage, including a first. Some people want an answer straight away; others prefer to wait. Both are reasonable, and there is no pressure either way.

A result can show whether a loss was a one-off chromosomal event, which is often reassuring for future pregnancies, or whether a pattern is worth exploring further, such as an inherited chromosomal rearrangement carried by one parent. POC testing sits within London Pregnancy Clinic's wider genetic testing and counselling service, which is designed to help you make sense of these findings.

Several laboratory methods can be used, and the right one depends on the sample and on what your clinician is looking for. Traditional karyotyping grows (cultures) living cells from the tissue and photographs the full set of 46 chromosomes, so a specialist can see chromosomes that are missing, extra or rearranged. It is reliable but depends on the cells growing successfully, which is not always possible. Read more on our karyotype and chromosome analysis page.

QF-PCR is a rapid DNA-based test that checks a selected group of chromosomes for an extra or missing copy — usually 13, 18 and 21 plus the sex chromosomes, although some laboratories add others, such as 15, 16 and 22. It can also pick up triploidy and signs that the mother's cells, rather than the pregnancy's, have been tested.

Chromosomal microarray goes further still, reading DNA across all the chromosomes at higher resolution to detect smaller missing or duplicated segments; because it uses DNA rather than dividing cells, it fails less often, although it cannot detect a perfectly balanced rearrangement.

Microarrays come in two main kinds. A SNP array also reads tiny 'spelling' differences in the DNA, so it can recognise triploidy (a whole extra set of chromosomes) and show when a sample is really the mother's tissue; array-CGH cannot do either as reliably. In NHS laboratories the rapid test often comes first, with a microarray if that result is normal.

• Karyotyping — grows living cells to view all 46 chromosomes; reliable, but can fail if the cells do not grow.
• QF-PCR — a rapid DNA test that checks selected chromosomes, usually 13, 18, 21 and the sex chromosomes X and Y.
• Chromosomal microarray — reads DNA directly, spots smaller changes and fails less often, but cannot see balanced rearrangements.

How the tissue is collected depends on how the miscarriage is managed. It may be obtained during surgical management (a minor procedure to remove the tissue), after medical management (using medication to help the tissue pass), or from tissue passed naturally at home, which can sometimes be brought in for testing.

For the best chance of a usable result, the tissue is placed in a clean, sterile container and kept cool. It should not be preserved in formalin, the preservative used for routine pathology, which can prevent tests from working; NHS genetics laboratories treat formalin-preserved tissue as unsuitable. Timing matters, so where a loss is anticipated it helps to plan testing in advance, and your clinical team will advise on how to collect and store the sample.

We understand that handling pregnancy tissue is emotionally difficult, and there is no right or wrong choice here. Whether to pursue testing is always entirely your decision, and you will be supported whatever you decide.

At its most helpful, POC testing can identify a chromosomal cause for the miscarriage, such as an extra copy of a chromosome (a trisomy) or a missing sex chromosome. Where the cause is a random chromosomal event, this is frequently reassuring, as it does not usually point to an ongoing problem in either parent.

The RCOG notes that, for women of the same age, a chance chromosomal cause is linked with a better outlook in the next pregnancy than a loss with normal chromosomes. Occasionally a finding suggests that both parents should have their own chromosomes checked.

The test has real limits, though. It does not always produce an answer: the tissue may be unavailable, too degraded, or unable to grow in the laboratory. Standard chromosome testing also does not examine individual genes unless this is specifically requested, so it will not detect single-gene conditions.

It is also important to understand that a normal result does not always mean the cause is known — only that a chromosome problem was not found. One further limitation is maternal cell contamination, where the mother's own cells are analysed instead of the pregnancy tissue, which can give a misleading "normal female" result. Modern techniques, such as SNP arrays, QF-PCR and comparison with a sample of the mother's blood, reduce, but do not entirely remove, this possibility.

Results usually fall into one of the groups below. Our guide to understanding miscarriage genetic test results explains each in more depth, and chromosomal causes of miscarriage covers why they happen.

Results are rarely a simple yes or no. A genetic counsellor or clinical geneticist can explain what a particular finding means for you, whether it was most likely a chance event, and whether further steps — such as testing both parents' chromosomes — are worth considering. Booking a clinical genetics consultation gives you the space to talk your results through with a specialist who understands both the science and the emotional weight of pregnancy loss.

At London Pregnancy Clinic we provide compassionate, unhurried genetic counselling before and after testing, and we arrange the laboratory analysis through accredited partners. If results point towards an inherited factor, we can guide you on what this might mean and on the options available for a future pregnancy.