The bright white circle center-right is the head, which faces to the left.Features include the forehead at 10 o'clock, the left ear toward the center at 7 o'clock and the right hand covering the eyes at .Crown/rump length and gestational age are closely compared with each other until around the end of the first trimester.The ideal time for a sonographer to assess the gestational age in the first trimester is between 7-10 weeks of pregnancy.In addition, although a woman is most likely to become pregnant if she has sex on the day of ovulation conception may also occur from live sperm still in her reproductive tract on the day of ovulation if she had sex for up to five days before ovulation [26,27]. Determining the Estimated Due Date The estimated due date (EDD or EDC) is the date that spontaneous onset of labor is expected to occur. Conceptional age, menstrual age, and ultrasound age: a second-trimester comparison of pregnancies of known conception date with pregnancies dated from the last menstrual period.
Fortunately, gestational sac, yolk sac and embryo are surrounded by hyperechoic (brighter) body tissues.
The International Society of Ultrasound in Obstetrics and Gynecology (ISUOG) recommends that pregnant women have routine obstetric ultrasounds between 18 weeks and 22 weeks gestational age in order to confirm pregnancy timing, to measure the fetus so that growth abnormalities can be recognized quickly later in pregnancy, and to assess for congenital malformations and multiple gestations (i.e. Additionally, the ISUOG recommends that pregnant women have obstetric ultrasounds between 11 weeks and 13 weeks 6 days gestational age in countries with resources to perform them.
Performing an ultrasound at this early stage of pregnancy can more accurately confirm the timing of the pregnancy and can also assess for multiple fetuses and major congenital abnormalities at an earlier stage.
Determining the Date of Conception Because the human egg is capable of fertilization for only 12 to 24 hours after ovulation the date of ovulation may be taken as being the date of conception.
However, ultrasound determination of the date of ovulation has the same imprecision as does the ultrasound estimate of the gestational age and, therefore, a precise date of conception cannot usually be determined as with in vitro fertilization.
Other reasons to have a 7 week ultrasound are to: The embryo will be measured from the top of its head, the “crown” to its bottom or “rump”.