Weeks 3 and 4 of Pregnancy: How Do I Prepare Myself For This Journey Of Pregnancy? The union of the egg and sperm during fertilization marks the beginning of your child's growth. The fertilized egg develops into a blastocyst, a group of cells, this week from a one-cell zygote. Your small kid is roughly the size of a pinhead and measures 0.1–0.2 mm (100–200 microns) from zygote to blastocyst. To learn more, see our blog post on first month of pregnancy symptoms. https://www.thevoiceofwoman.com/3-to-4-weeks-pregnant #pregnancy #fertilization #growth #zygote #blastocyst #blog #woman #blogwebsite #Business #Health #thevoiceofwoman