Non-invasive prenatal testing (NIPT) arrived in 2011 and transformed pregnancy screening. A simple blood test sweeps the mother's bloodstream for scraps of placental DNA, uncovering fetal genetic defects and shedding light on the health of the unborn baby. The tests are routinely offered in rich countries from the tenth week of pregnancy onwards.
NIPT scours the mother's blood for DNA fragments and maps them to their chromosome of origin. Around 10% of the fragments come from the placenta, which usually has identical DNA to the developing fetus. If the percentage of DNA linked to a particular chromosome is unusually high or low, it may point to a fetal abnormality. Approximately three in 1,000 results come back as inconclusive.
A study published in the New England Journal of Medicine in December 2025 gave full-body MRI scans to about 100 women with inconclusive NIPT findings. In half of these cases the results were linked to false positives, maternal conditions or unknown causes. In the other half, the scans revealed the mothers had cancer—their prenatal-test results had been scrambled by tumour DNA shed into the bloodstream. The Netherlands and Belgium now offer genetic counselling and whole-body MRIs to anyone with inconclusive prenatal-test results.
A paper published in Nature Medicine in February 2026, by Gavin Ha of Fred Hutchinson Cancer Centre in Seattle and Raj Shree of the University of Washington, used a machine-learning algorithm to categorise DNA from standard prenatal tests of almost a thousand women. Pregnant women who go on to develop pre-eclampsia have slightly less placental DNA in their blood and slightly more DNA from the lining of their blood vessels. The model could predict pre-eclampsia with 80% accuracy by the 16th week of pregnancy, well before clinical signs appeared.
Testing pregnant women's blood for certain proteins, or the molecules regulating their production, can predict almost 90% of preterm births between weeks six and 20 of pregnancy. American biotech companies Mirvie and Sera Prognostics sell pre-eclampsia and preterm-birth tests directly to consumers, at costs ranging from $750 to $1,850.
Early detection does not always translate into prompt treatment. Many common cancer therapies, including chemotherapy and surgery, can be extremely risky during pregnancy. The only proven method to reduce the risk of pre-eclampsia and preterm births is a course of aspirin, which is already widely recommended for pregnant women.
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