Human Embryonic Development and the Clinical Study of Miscarriage Risks
A 9-Week Human Embryo from Ectopic Pregnancy provides significant insight into early development. The size and anatomic features suggest development equivalent to a nine-week pregnancy (or seven weeks post ovulation). In obstetrics, pregnancy is dated from the first day of the last menstrual period, which is about two weeks prior to the ovulation that resulted in the pregnancy.
Research on Embryo Growth and Miscarriage
According to clinical observations, miscarriages may be more likely to occur with slow developing embryos. Using vaginal ultrasound scans to build detailed 3D images that show an embryo's growth could predict which pregnancies are most likely to end in miscarriage. 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. 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.
The Carnegie Staging System and Developmental Milestones
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.
Key Research Findings
- Miscarriage Risk: Increased by 1.5 per cent per delayed Carnegie stage.
- Developmental Delay: Embryos that went on to miscarry were delayed by about four days at eight weeks post-conception.
- Assessment Tool: Carnegie staging system (23-stage scale).
- Methodology: Vaginal ultrasound scans used to build highly detailed 3D images visualized through virtual reality.
Factors Influencing Pregnancy Outcomes
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. 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. While 3D embryo imaging may reassure some people, it could also cause uncertainty and anxiety for those who have previously had a miscarriage.