We cannot mention a particular week, but we can say that they occur within the first 20 weeks of pregnancy, and most of them in the first 12 weeks.
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Bachelor's Degree in Biotechnology from the Polytechnic University of Valencia. Master's Degree in Biotechnology of Human Assisted Reproduction from the University of Valencia along with the Valencian Infertility Institute (IVI). Postgraduate course in Medical Genetics.