Yes its true,
Older women are not the only ones prone to having defective eggs – young women have flaws in about half of theirs too, two separate studies suggest.
It had always just been assumed that young women’s eggs were in good shape. “We made some assumptions, but we were wrong,” says Jeffrey Nelson of the Huntington Reproductive Center in Pasadena, California, US, who led one study.
It is well known that women over the age of 38 are more likely to conceive offspring with chromosomal problems, known as aneuploidies – where too many or too few chromosomes are present. Down’s syndrome, for example, is caused by an extra chromosome 21.
Preimplantation genetic diagnosis (PGD) – a technique in which a cell from an early-stage embryo is examined for such abnormalities before being used for IVF treatment – has confirmed that older women’s eggs are riddled with abnormalities. But until now, no one had systematically studied the eggs of younger women for flaws.
Paulette Browne, at the Shady Grove Center for Preimplantation Genetics in Rockville, Maryland, US, and her colleagues, examined 275 embryos created from the donated eggs of women aged between 21 and 31. All the donors were ostensibly healthy. The researchers removed cells three days after conception and examined them for aneuploidies. They found that 137 – half – of the embryos had at least one error.
In a similar study, Nelson and colleagues looked at 289 embryos created using eggs from 22 donors under the age of 30. About 42% had chromosomal problems. “Initially, it shocked me,” says Nelson. The studies were presented at a meeting of the American Society for Reproductive Medicine in Montreal, Canada, on Monday.
Browne suggests that perhaps there is an underlying chromosomal abnormality rate in the eggs of all healthy women. Many healthy women have miscarriages, and most are thought to be the result of chromosomal problems.
But Nelson’s data uncovered a great variation between women in terms of how many eggs were defective – from 29% to 83%. “It’s hard to know exactly what happens in the normal population,” says Zsolt Nagy, at Reproductive Biology Associates in Atlanta, Georgia, US.
The researchers admit that the quality of the eggs might somehow be compromised by the process of obtaining them for IVF – which involves hyper-stimulating the ovary. Alternatively, the flawed embryos might have nothing to do with the donor eggs, and could be a result of problem sperm.