Talk:Fetal Development - 18 Weeks

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Cite this page: Hill, M.A. (2021, May 16) Embryology Fetal Development - 18 Weeks. Retrieved from


Prediction of newborn birth weight based on the estimation at 20-24 weeks of gestation

Taiwan J Obstet Gynecol. 2010 Sep;49(3):285-90.

Su CF, Tsai HJ, Lin CY, Ying TH, Wang PH, Chen GD. Source Department of Obstetrics and Gynecology, Kuang Tien General Hospital, Taichung, Taiwan. Abstract OBJECTIVE: The aim of this study was to develop a mathematical equation to predict the birth weight during the second trimester at 20-24 weeks of gestation. MATERIALS AND METHODS: In a university hospital, 110 healthy pregnant women were eligible for inclusion at 20-24 weeks of gestation. We recorded the maternal weight (pre-pregnancy, mid-pregnancy, and at delivery) and body mass index (BMI), newborn birth weight, time period from ultrasound examination to term delivery, and also the fetal biometrics sonographically at 20-24 weeks of gestation. Pearson's correlation was used to verify the extent of the relationship between all the above measurements and the newborn birth weight. Multiple regressions with the stepwise method were used to analyze maternal weight factors, fetal biometrical factors, and pregnancy interval. An equation for term birth weight estimation during the second trimester was determined. RESULTS: Maternal BMI at mid-pregnancy, time interval from mid-pregnancy to term, and abdominal circumference had the highest correlation with newborn birth weight (r = 0.388, 0.341, and 0.315, respectively, p < 0.05). Using the stepwise regression analysis, an optimal formula with variance of 0.303 was derived: estimated birth weight = -700 + 49.766 × (mid-pregnancy BMI [kg/m2]) + 13.362 × (time interval from mid-pregnancy to term delivery [days]) + 68.696 × (abdominal circumference [cm]). CONCLUSION: We propose an accurate, simple, and easy formula to better assess the newborn birth weight at mid-pregnancy for the Asian population. Mid-pregnancy BMI was a more significant factor for birth weight estimation than other maternal weight factors in this study. Copyright © 2010 Taiwan Association of Obstetric & Gynecology. Published by Elsevier B.V. All rights reserved.

PMID 21056312

Normative data of cervical length in singleton pregnancy in women attending a tertiary care hospital in eastern India

Indian J Med Res. 2011 May;133(5):492-6.

Mukherji J, Anant M, Ghosh S, Bhattacharyya SK, Hazra A, Kamilya GS. Source Department of Obstetrics & Gynecology, R. G. Kar Medical College & Hospital, Kolkata, India.


BACKGROUND & OBJECTIVES: The length of cervix predicts the risk of preterm delivery. The objective of this study was to assess cervical length in pregnancy by transvaginal ultrasonography for generating normative data for nulliparous women at no special risk of preterm labour. METHODS: An observational study was carried out in a tertiary care teaching hospital in eastern India in nulliparous women who delivered at term. A single sonologist assessed 224 women (once per subject) between 20 and 34 wk of gestation. Nulliparous women carrying a single foetus of confirmed gestational age were included; 216 subjects were finally considered for generation of normative data, excluding those delivering earlier than 37 or later than 42 wk. Other exclusion criteria were history of cerclage, any previous cervical surgery, smoking, or any medical disorder complicating pregnancy. RESULTS: Cervix length at each week of gestation gradually decreased over the study period. Length at 20 and 34 wk was 40.5 ± 1.14 mm (mean ± SD) and 34.8 ± 1.34 mm respectively. The overall shortening over this 14 wk period was 5.7 mm, with 0.58 mm per week median rate of shortening. Pearson's correlation coefficient was -0.69 (95% CI -0.75 to -0.60; P< 0.001) for cervical length vis-à-vis gestational age. INTERPRETATION & CONCLUSIONS: The serial normative data generated in our setting can be used to decide cut-off points for predicting risk of preterm labour in future studies. Validity of such prediction needs to be tested in larger cohorts of women assessed at specific gestational ages.

PMID 21623033;year=2011;volume=133;issue=5;spage=492;epage=496;aulast=Mukherji


Sonographic evaluation of the fetal conus medullaris at 20 to 24 weeks' gestation

Prenat Diagn. 2010 Sep;30(9):862-4. doi: 10.1002/pd.2572.

Perlitz Y1, Izhaki I, Ben-Ami M. Author information Abstract OBJECTIVE: To determine the normal level of the conus medullaris (CM) of the spinal cord of normal fetuses at 20 to 24 weeks' gestation using abdominal sonography. METHODS: Using a 4 to 8 MHz ultrasound abdominal transducer, CM was imaged in the midsagittal plane with the fetal spine facing toward the transducer. The CM ending level was located by counting the vertebrae caudal starting at T12, which was identified by lowest fetal rib. The CM locations were defined according to their positions relative to the vertebrae. RESULTS: One hundred and ten consecutive pregnant women were included in the study. The CM was clearly demonstrated in 78 (71%) of these cases. Most of the scanned fetuses had the CM ending height adjacent to vertebrae L2, L2-3 inter-space and L3 (73/78, 93%). The L1-2, L2, L2-3, and L3 vertebral groups did not differ in mean gestational weeks, maternal age, or fetal gender. CONCLUSION: The level of the CM can be determined at 20 to 24 weeks' gestation in about 70% of fetuses. Most of the scanned fetuses had the CM ending height adjacent to vertebrae L2, L2-3 vertebral space, and L3 (73/78, 93%). When detected lower than the third lumbar vertebra it should prompt prenatal and postnatal surveillance. (c) 2010 John Wiley & Sons, Ltd. PMID 20582935