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			Concern Treatment Pregnancy Experiences Pregnancy Maintaining Your Pregnancy Hormonal Support Role of Hormones Hormonal Changes		Hormonal Support Following fertilisation, the fertilised ovum or embryo begins to develop within the fallopian tube through cell division.  The first stage of division, following breakdown of the pronuclei (the nucleus of a sperm or egg before fusion), produces a complete cell nucleus with a chromosomal structure determined by the particular sperm and egg cells.  Successive cell divisions occur every 12 to 14 hours. At anywhere from 72 to 96 hours after fertilisation, a solid, spherical mass of cells, known as a morula, develops. As the cells of the morula continue to divide, a hollow ball of approximately 32 cells called a blastocyst forms, consisting of an outer layer of cells and an inner cell mass.  The cells that form the outer layer of the blastocyst make up the trophoblast. This layer of cells will eventually become part of the placenta, the structure that anchors the foetus to the uterus.  The embryo remains in the fallopian tube for 3 to 4 days, being slowly carried to the uterus.  A number of factors enhance the ability of the embryo to implant in the uterine wall, in particular an appropriate balance of hormones. The endometrial lining develops in response to circulating progesterone and oestrogen secreted by the corpus luteum, and a deficiency of these hormones can impair implantation.
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