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Cite this page: Hill, M.A. (2019, September 20) Embryology Second Trimester. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Talk:Second_Trimester
Second trimester sonographic features of fetal chromosomal defects
Mymensingh Med J. 2014 Apr;23(2):412-6.
Akhter N1, Chakraborty RK.
Advances in ultrasound technology have dramatically improved the detection of fetal chromosomal defects. Each chromosomal defect has its own syndromal pattern of detectable abnormalities prenataly. Most commonly detectable defects are Trisomies & Triploidies. Although only an invasive test can provide a definitive diagnosis, fetuses with major chromosomal abnormalities have either external or internal defects that can be recognized by detailed ultrasonographic examination at second trimester. These are defined as ultrasound markers for fetal aneuploidy. This article provides an overview and discussion on prenatal sonographic features that may suggest the presence of a common fetal chromosomal defect.
Fetal size in the second trimester is associated with the duration of pregnancy, small fetuses having longer pregnancies
BMC Pregnancy Childbirth. 2008 Jul 16;8:25. doi: 10.1186/1471-2393-8-25.
Johnsen SL1, Wilsgaard T, Rasmussen S, Hanson MA, Godfrey KM, Kiserud T. Author information Abstract BACKGROUND: Conventionally, the pregnancy duration is accepted to be 280-282 days. Fetuses determined by ultrasound biometry to be small in early pregnancy, have an increased risk of premature birth. We speculate that the higher rate of preterm delivery in such small fetuses represents a pathological outcome not applicable to physiological pregnancies. Here we test the hypothesis that in low-risk pregnancies fetal growth (expressed by fetal size in the second trimester) is itself a determinant for pregnancy duration with the slower growing fetuses having a longer pregnancy. METHODS: We analysed duration of gestation data for 541 women who had a spontaneous delivery having previously been recruited to a cross-sectional study of 650 low-risk pregnancies. All had a regular menses and a known date of their last menstrual period (LMP). Subjects were examined using ultrasound to determine fetal head circumference (HC), abdominal circumference (AC) and femur length (FL) at 10-24 weeks of gestation. Length of the pregnancy was calculated from LMP, and birth weights were noted. The effect of fetal size at 10-24 weeks of gestation on pregnancy duration was assessed also when adjusting for the difference between LMP and ultrasound based fetal age. RESULTS: Small fetuses (z-score -2.5) at second trimester ultrasound scan had lower birth weights (p < 0.0001) and longer duration of pregnancy (p < 0.0001) than large fetuses (z-score +2.5): 289.6 days (95%CI 288.0 to 291.1) vs. 276.1 (95%CI 273.6 to 278.4) for HC, 289.0 days (95%CI 287.4 to 290.6) vs. 276.9 days (95%CI 274.4 to 279.2) for AC and 288.3 vs. 277.9 days (95%CI 275.6 to 280.1) for FL. Controlling for the difference between LMP and ultrasound dating (using HC measurement), the effect of fetal size on pregnancy length was reduced to half but was still present for AC and FL (comparing z-score -2.5 with +2.5, 286.6 vs. 280.2 days, p = 0.004, and 286.0 vs. 280.9, p = 0.008, respectively). CONCLUSION: Fetal size in the second trimester is a determinant of birth weight and pregnancy duration, small fetuses having lower birth weights and longer pregnancies (up to 13 days compared with large fetuses). Our results support a concept of individually assigned pregnancy duration according to growth rates rather than imposing a standard of 280-282 days on all pregnancies. PMID 18627638