The germinal stage of development is the first and shortest of the stages of the human lifespan. It lasts roughly eight to nine days, beginning with fertilization and ending with implantation in the endometrium of the uterus, after which the developing organism is called an embryo.Click to see full answer. Moreover, which fetal development stage is the shortest longest?- The shortest stage in development is the germinal and the longest is the fetal period.Similarly, what is the longest stage of development? The longest period of prenatal development is the fetal period which begins at the 9th week after conception and lasts until birth. By the 12th week, the genitals have formed. Development of all the structures of the body continues and by the end of the third month, all structures are present although immature. In this manner, which stage of prenatal development begins with conception? The first 2 weeks of development is the germinal period. The germinal period begins with conception and ends when the blastocyst is fully implanted into uterine tissue. Next, the embryonic period lasts from implantation until about 8 weeks from the time of conception.How long is the germinal stage?The germinal period (about 14 days in length) lasts from conception to implantation of the zygote (fertilized egg) in the lining of the uterus. During this time, the organism begins cell division and growth.