Berry E, Aitken D A, Crossley J A, Macri J N, Connor J M
Duncan Guthrie Institute of Medical Genetics, Yorkhill Hospital, Glasgow, U.K.
Prenat Diagn. 1995 Jun;15(6):555-65. doi: 10.1002/pd.1970150609.
The aim of this study was to determine the maternal population, pregnancy, serum alpha-fetoprotein (AFP) and free beta subunit of human chorionic gonadotrophin (F beta hCG) parameters in a large series of women attending prenatal clinics before 15 weeks' gestation and to assess the practical problems of population screening for Down's syndrome in the first trimester using these markers. Serum samples were collected from 8600 women attending prenatal clinic booking visits. Maternal serum AFP and F beta hCG medians were calculated for each day of gestation (49-104 days), using both dates and ultrasound estimates of gestation. The effects of maternal weight, twin pregnancies, and threatened abortion on AFP and F beta hCG levels were analysed. The median age of the population was 27.1 years and the median weight 62.1 kg. Twenty-six per cent of samples were collected before 70 days and 50 per cent before 78 days' gestation. Eighty-nine per cent of all samples had gestational estimates by dates, 60 per cent by ultrasound and 52 per cent by both dates and ultrasound. The AFP median was 5 kU/l at 49 days, 5.9 kU/l at 70 days, and 17.9 kU/l at 100 days. The peak median F beta hCG level was 66.4 ng/ml at 64 days, falling to 20.6 ng/ml at 100 days' gestation. Both AFP and F beta hCG levels showed log Gaussian distributions but the standard deviation for AFP was 20 per cent greater than that found in the second trimester. AFP and F beta hCG levels showed an inverse relationship with maternal weight and were increased in twin pregnancies (1.68 and 1.97 multiples of the median, respectively). AFP and F beta hCG can be readily measured in a large screening population in the first trimester. Down's syndrome screening protocols based on these markers could be refined by the use of gestations in individual days but AFP is likely to be a less effective marker and detection rates are likely to be lower than in the second trimester. To realize the potential of first-trimester screening, more women should be encouraged to attend the prenatal clinic in early pregnancy and ultrasound dating should be carried out for all pregnancies at this stage.
本研究的目的是确定一大群妊娠15周前到产前诊所就诊的孕妇的母体人群、妊娠情况、血清甲胎蛋白（AFP）和人绒毛膜促性腺激素游离β亚基（FβhCG）参数，并评估使用这些标志物在孕早期进行唐氏综合征人群筛查的实际问题。从8600名到产前诊所进行预约就诊的妇女中采集血清样本。使用妊娠日期和超声估计妊娠时间，计算妊娠各日（49 - 104天）的母体血清AFP和FβhCG中位数。分析了母体体重、双胎妊娠和先兆流产对AFP和FβhCG水平的影响。人群的中位年龄为27.1岁，中位体重为62.1千克。26%的样本在妊娠70天前采集，50%在妊娠78天前采集。所有样本中，89%通过日期估计妊娠时间，60%通过超声估计，52%通过日期和超声两者估计。AFP中位数在49天时为5 kU/l，70天时为5.9 kU/l，100天时为17.9 kU/l。FβhCG水平的中位峰值在64天时为66.4 ng/ml，在妊娠100天时降至20.6 ng/ml。AFP和FβhCG水平均呈对数高斯分布，但AFP的标准差比孕中期发现的标准差大20%。AFP和FβhCG水平与母体体重呈负相关，在双胎妊娠中升高（分别为中位数的1.68倍和1.97倍）。AFP和FβhCG在孕早期的大规模筛查人群中易于测量。基于这些标志物的唐氏综合征筛查方案可通过使用具体日期的妊娠时间进行优化，但AFP可能是一个效果较差的标志物，检测率可能低于孕中期。为了实现孕早期筛查的潜力，应鼓励更多妇女在孕早期到产前诊所就诊，并且在此阶段应对所有妊娠进行超声确定孕周。
