Embryos may develop more slowly in certain pregnancies that end in miscarriage, according to a study that uses virtual reality to visualise them using vaginal ultrasound scans.
The finding could be a step towards predicting from early in a pregnancy if it is likely to lead to a miscarriage, although the technique isn’t yet ready for clinical use, says Melek Rousian at Erasmus University Medical Centre in Rotterdam, the Netherlands.
More than half of all pregnancies end in miscarriage, although in many cases it happens so early that people don’t even realise they were pregnant. Some people have multiple miscarriages without knowing why, meaning their pregnancies can be a time of great anxiety.
To find out more about why miscarriages occur, Rousian’s team developed a way of using vaginal ultrasound scans to build a highly detailed 3D image of an embryo. The image is magnified until it is about the size of an adult and then visually inspected by the researchers while they wear virtual reality headsets.
The team created these images for 644 pregnant women, 33 of whom went on to have miscarriages. Transgender people weren’t included in the study.
When looking at the 3D images, produced at around eight weeks post-conception, the researchers saw that, on average, the embryos that eventually miscarried were developing more slowly, compared with the pregnancies that continued to term.
Embryo maturity was assessed via the so-called Carnegie staging system, which indicates which physical features have developed, such as limb buds and early facial features, according to a 23-stage scale.
The team found that the chance a woman would miscarry rose by 1.5 per cent per delayed Carnegie stage.
At eight weeks post-conception, this was equivalent to the embryos that went on to miscarry being delayed in development by about four days, according to the researchers. “Four days is quite a large gap in a very important period of life when all the organs are developing, all limbs are developing,” says team member Carsten Pietersma.
If the findings are confirmed in larger studies, this may allow doctors to advise people whether or not their embryo is developing normally, says Rousian.
It is unknown exactly why embryos that develop more slowly may be more likely to miscarry. Other work has found that embryos or fetuses that miscarry often have alterations to or different numbers of chromosomes, the packages of DNA contained in nearly all our cells.
Ruth Bender Atik at the Miscarriage Association, a UK support charity, says that although the 3D embryo imaging may reassure some people, it could also cause uncertainty and anxiety.
Some people who have previously had a miscarriage may not want the vaginal ultrasound scan, while others could be desperate to check the progress of their pregnancy, she says.