Page 2 - Fetalage Conception Guidline

 
At this stage, the menstrual period has just ended and your body is getting ready for ovulation. For most women, ovulation takes place about 11 - 21 days from the first day of the last menstrual period. During intercourse, several hundred million sperm are released in the vagina. Sperm will travel through the cervix and into the fallopian tubes. When conception takes place, the sperm will penetrate an egg and create a single set of 46 chromosomes called a zygote - the basis for a new human being. The fertilized egg, called a morula, spends a couple of days traveling through the fallopian tube toward the uterus and dividing into cells (this dividing process is where many chromosomal abnormalities occur). The morula becomes a blastocyst and will eventually end up in the uterus. Anywhere from day 6 - 12 after conception, the blastocyst will imbed into the uterine lining and begin the embryonic stage.
Weeks 3-4 - Gestational Age (Fetal Age 2 weeks)
Development
The earliest change that can be seen through a vaginal ultrasound at this time will be the “decidual reaction” which is the thickening of the endometrium. The endometrium lining thickens as the blastocyst burrows into it. This cannot always be detected by ultrasound—sometimes it may take a special eye or very good equipment to see this “reaction” in the endometrium lining.
*A key fact to remember when using ultrasounds is that a transvaginal ultrasound can detect development in the uterus about a week earlier than a transabdominal ultrasound.
Hormones