The endometrium only allows healthy embryos to grow into a baby. This has become clear from the doctoral research of gynecologist in training Gijs Teklenburg of the University Medical Center (UMC) Utrecht.
“Human reproduction is unusually ineffective, says gynecologist in training Gijs Teklenburg. The chance of one pregnancy per menstrual cycle is only twenty percent in a healthy couple. This is not strange however, when you consider that many embryos are of a poor quality. For example, they do not have the right number of chromosomes.
In his doctoral research, Teklenburg questioned how the body selects the right embryos. For this purpose, he analyzed the biological activity in the endometrium during human embryo implantation. Teklenburg determined the levels of fourteen implantation factors. He imitated the natural situation using cultured cells from the endometrium.
The results of the experiments were that three quarters of the implanted embryos did not manage to attach to the endometrial wall – only one quarter did. Apparently if embryos do develop successfully, there are only a few changes visible in the endometrium. However, if embryos are ‘bad’, i.e. they are often rejected later, there are many changes in the endometrium. It looks as if the endometrium is receptive to implantation but then goes on to actively reject bad embryos. The endometrium therefore selects embryos according to quality.
Teklenburg confirmed his findings in a study conducted in women who had had repeated (three or more) miscarriages. He analyzed cells from the endometrium of these women. In these women, the endometrium did indeed react differently. Teklenburg: “Through the lack of natural embryo selection, these patients get pregnant quickly but miscarriage results more often.” These results were published in April 2010 in two articles published in the journal PLoS ONE.
Gijs Teklenburg was awarded his PhD from Utrecht University on December 7, 2010. His doctoral thesis has the title: Preimplantation embryo-endometrial signalling. Teklenburg’s research was supervised by Professor Nick Macklon and Professor Cobi Heijnen.