Below is a timeline that I composted from various textbooks and the Internet regarding the timeline of pregnancy. This is the first in a multi-part series on fetal development and pregnancy. There is a lot of varying information out there about this topic, some more accurate than others, and I tried to include what I felt to be the most accurate.
Conception happens when the sperm enters the egg, which usually takes place in the fallopian tubes. As soon as the sperm and egg unite, the gender, hair, skin and eye color of the new baby are already determined. Fertilization usually takes about 24 hours.
30 Hours After Conception
The new baby cells divide and subdivide as it is swept through the fallopian tube by cilia toward the uterus.
3-4 Days After Conception
3-4 days after conception the fertilized egg arrives at the uterus after a 4 inch journey through the fallopian tube. The cells look like a microscopic mulberry or raspberry and are called a morula. Once in the uterus it burrows itself into the endometrium, which is the lining of the uterus. The outside cells of the morula eventually grow to form the placenta. Baby begins to develop from the inner layer of cells.
6-7 Days After Conception
The morula, now dubbed a blastocyst because of various changes, begins to attach to the uterus. This is when some women report feeling implantation cramps that feel like mild menstrual cramps.
7-10 Days After Conception
Implantation may or may not be followed by implantation bleeding, which looks like light spotting. Once the blastocyst is implanted, baby is deriving nourishment from maternal tissues.
7-9 Days After Conception
This is the earliest time period when a labratory blood pregnancy test can detect the levels of hCG hormone in your body. hCG (human Chorionic Gonadotropin) is a protein hormone that is first produced in the second week of gestation. It prevents menstruation and is most concentrated at 8 weeks gestation. Levels gradually decline after the 8th week.
2 Weeks After Conception
This is the magic time when most women discovery they are pregnant via the results of a home urine pregnancy tests. These tests are 95% accurate in detecting hCG in the body.
Anne Frye states that during the first two weeks after fertilization the pre-embryo is usually not susceptible to toxins. When damage does occur it usually disrupts most or all of the cells, resulting in death. Or it may damage only a few cells, from which baby can recover and go on to develop defect-free. It is during the first 8 weeks of gestation that baby is most sensitive to major damage.
Spiritual Midwifery, Ina Mae Gaskin, 289
Holistic Midwifery Volume 1, Anne Frye, 673-678