Prenatal diagnosis of achondroplasia in the second trimester of pregnancy using the biparietal diameter/femur length ratio

Purpose: To investigate the accuracy of ultrasound dating formulae in the late second trimester of pregnancy. Material and Methods: A dataset of 136 singleton pregnancies conceived by artificial reproductive techniques was studied to assess the accuracy of ultrasound dating formulae in the late second trimester, and compared with early second trimester. A total of 21 published ultrasound-dating formulae were tested. Results: For most formulae, late second trimester scans yielded results that were marginally less accurate than the early second trimester. The best performance was obtained with dating formulae based on femur length, either alone or combined with the biparietal diameter. These formulae had mean absolute errors of 3–3.5 days. Combining two or more parameters did not result in any substantial gain in accuracy. Conclusions: Pregnancy dating by ultrasound in the late second trimester is sufficiently accurate for routine clinical use. Formulae based on femur length appear to be at least as accurate as head measurements.

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Second trimester placental thickness: its’ correlation with gestational age, femur length and biparietal diameter

International Journal of Reproduction Contraception Obstetrics and Gynecology ◽

10.18203/2320-1770.ijrcog20183461 ◽

2018 ◽

Vol 7 (9) ◽

pp. 3568

Author(s):

Sandesh Ganjoo ◽

Shalini Devgan ◽

Ghanshyam Dev

Keyword(s):

Gestational Age ◽

First Trimester ◽

Uterine Wall ◽

Second Trimester ◽

Cross Sectional ◽

Femur Length ◽

Biparietal Diameter ◽

Positive Linear Correlation ◽

Minimum Age ◽

Placental Thickness

Background: Placental thickness (PT) is the easiest placental dimension to measure, yet little is known about the normal PT. The aim of this study was to determine the normal, sonographically measured PT in millimetre (mm) in the second trimester and to determine if this measurement can be adjusted for gestational age for that time and evaluate its relationship with femur length and biparietal diameter of the fetus.Methods: The study was a cross sectional observational study, recruiting 100 consecutive, singleton pregnancies, reporting for ultrasonography (USG) between 14 weeks and 24 weeks of gestation, having undergone at least one ultrasonogram in the first trimester, with known last menstrual period (LMP). The placental thickness was measured perpendicular to the uterine wall, through the placenta at the site of cord insertion.Results: The average age of study population was 24.96 with a standard deviation (SD) of 2.70 years with the minimum age being 18 years and maximum age being 32 years. Regression analysis yielded the following mathematical relationships between PT, Gestational age (GA), Biparietal diameter (BPD) and Femur length (FL) in the second trimester. Y(PT)= 0.9366x (Gestation age)+1.655, R2 = 0.7332; Y(PT)= 0.2872x(BPD)+6.9578, R2= 0.7314; Y(PT)=0.2995x(FL)+ 10.03, R2 = 0.6186Conclusions: PT in present study showed a positive linear correlation with gestational age, FL and BPD in second trimester. Also, it can be concluded that PT may be used as a predictor of GA in women with unknown LMP.

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