EMBRYO, ULTRASOUND BIOMETRY

The fertilized ovum or egg is a single cell termed the zygote. The zygote contains the combined genetic material of the spermatozoid and the ovum. After several divisions, the zygote forms a cluster of cells, called an embryo up to the age of 8 weeks, which implants in the uterus. Here is a colored ultrasound image of a 4-week-old embryo.