Department of Obstetrics and Gynecology, Fetal Medicine Unit and Department of Radiology, University Hospital Brugmann, Place A. Van Gehuchten 4, 1020 Brussels, Belgium.
Radiology. 2013 Jun;267(3):902-10. doi: 10.1148/radiol.12121374. Epub 2013 Jan 17.
To prospectively define fetal density in the second half of pregnancy by using magnetic resonance (MR) imaging and to compare estimates of fetal weight based on ultrasonography (US) and MR imaging with actual birth weight.
Written informed consent was obtained for this ethics committee-approved study. In this cross-sectional study between March 2011 and May 2012, fetal density was calculated as actual birth weight at delivery divided by fetal body volume at MR imaging in 188 fetuses between 20 weeks and 2 days and 42 weeks and 1 day of gestational age. Regression analysis was used to investigate the effect of variables, including sex, on fetal density. The US estimate of fetal weight was performed according to Hadlock et al, and the MR estimate of fetal weight was calculated based on the equation developed by Baker et al. US and MR estimates of fetal weight were compared with actual birth weights by using regression analysis.
Median fetal density was equal to 1.04 (range, 0.95-1.18). Fetal density was significantly associated with gestational age at delivery but not with fetal sex. In 26.6% of fetuses, the US estimate of fetal weight had a relative error of more than 10%, while a similar relative error for the MR estimate of fetal weight occurred in only 1.1% of fetuses. The limits of agreement were narrower with the MR estimate of fetal weight compared with the US estimate of fetal weight.
In the second half of pregnancy, fetal density varies with gestational age. Fetal weight estimates by using fetal MR imaging are better than those by using prenatal US.
通过磁共振成像（MR）前瞻性地定义妊娠后半期胎儿密度，并将基于超声（US）和 MR 成像的胎儿体重估计值与实际出生体重进行比较。
本研究获得伦理委员会批准，并经书面知情同意。在 2011 年 3 月至 2012 年 5 月进行的这项横断面研究中，188 例胎龄为 20 周至 2 天和 42 周至 1 天的胎儿，将实际出生体重除以 MR 成像时的胎儿体体积，计算出胎儿密度。回归分析用于研究变量（包括性别）对胎儿密度的影响。根据 Hadlock 等人的方法进行 US 估计胎儿体重，根据 Baker 等人的方程计算 MR 估计胎儿体重。通过回归分析比较 US 和 MR 估计胎儿体重与实际出生体重。
胎儿密度的中位数为 1.04（范围，0.95-1.18）。胎儿密度与分娩时的胎龄显著相关，但与胎儿性别无关。在 26.6%的胎儿中，US 估计胎儿体重的相对误差超过 10%，而 MR 估计胎儿体重的相对误差仅发生在 1.1%的胎儿中。与 US 估计胎儿体重相比，MR 估计胎儿体重的一致性区间更窄。
在妊娠后半期，胎儿密度随胎龄而变化。使用胎儿 MR 成像估计胎儿体重优于产前 US。
