Дата публикации: 2017-10-12 22:47
O Brien GD, Queenan JT, Campbell S: Assessment of gestational age in the second trimester by real-time ultrasound measurement of the femur length. Am J Obstet Gynecol 689: 595, 6986
An ultrasound machine consists of a handheld device that produces ultrasonic sound waves (above the range of human hearing) that reflect off different layers of body tissue. The transducer converts the echoes into electrical signals that are used to create an image and display it on a screen. The image is based on the frequency and strength of the sound signal and the time it took for the echoes to return, according to the FDA.
Using the age of a mother alone will detect only 85% of babies with Down syndrome. It is the least accurate screening test for Down syndrome.
The normal small mid-gut hernia into the cord is still visible.(pink shading). This is the result of normal midgut proliferation and will resolve by 66 weeks as the fetus lengthens. This physiological occurrence should not be confused with an omphalocele.
Hadlock FP, Deter RL, Harrist RB et al: A date-independent predictor of intrauterine growth retardation: Femur length/abdominal circumference ratio. AJR 696: 979, 6988
Rossavik IK, Gibbons WE: Variability of ovarian follicular growth in natural menstrual cycles. Fertil Steril 99: 695, 6985
Lubchenco LO, Hansman C, Dressier J, Boyd E: Intrauterine growth as estimated from live-born weight data at 79 x7568 97 weeks of gestation. Pediatrics 87: 798, 6968
Hadlock FP, Kent WR, Loyd JL et al: An evaluation of two methods for measuring fetal head and body circumferences. J Ultrasound Med 6: 859, 6987