Institute of Human Genetics, Medical University of Graz, Graz, Austria.
Placenta. 2011 Aug;32(8):611-5. doi: 10.1016/j.placenta.2011.03.009. Epub 2011 Jun 21.
Levels of SRY-specific cell free fetal DNA (SRY-cffDNA) in maternal plasma were investigated in twin pregnancies with two male fetuses versus one male and one female fetus and singleton male pregnancies during second and third trimester. The aim was to evaluate at which gestational age the amount of SRY-cffDNA reflects the number of fetuses and placentas respectively.
251 venous blood samples were analyzed from a total of 178 women with male or mixed-gender twin pregnancies and male singleton pregnancies in the second and the third trimester. The concentration of SRY-cffDNA was determined by quantitative real time PCR using the Y-chromosome specific SRY assay. For statistical analysis these three groups were divided into four subgroups according to their gestational age.
During second trimester levels of SRY-cffDNA showed no differences between twin and singleton pregnancies. After 28 weeks SRY-cffDNA of male twin pregnancies was significantly increased compared to singleton male pregnancies and mixed-gender twin pregnancies with no differences between the latter two.
The level of SRY-cffDNA in maternal serum of twin pregnancies reflects the number of fetuses only during the third trimester. Hence its use as a diagnostic tool for complications related to altered SRY-cffDNA levels in twin pregnancies should be evaluated at different weeks of gestation, especially during the second trimester.
研究母体血浆中性别决定区 Y 特异性游离胎儿 DNA（SRY-cffDNA）在双胎妊娠中两个男性胎儿与一个男性和一个女性胎儿以及单胎男性妊娠中第二和第三孕期的水平。目的是评估在哪个孕龄，SRY-cffDNA 的量分别反映胎儿和胎盘的数量。
分析了总共 178 名怀有男性或混合性别双胎妊娠和单胎男性妊娠的孕妇的 251 份静脉血样本。使用 Y 染色体特异性 SRY 测定法通过定量实时 PCR 确定 SRY-cffDNA 的浓度。为了进行统计分析，这三组根据其孕龄分为四个亚组。
在第二孕期，SRY-cffDNA 在双胎和单胎妊娠之间没有差异。28 周后，男性双胎妊娠的 SRY-cffDNA 水平明显高于单胎男性妊娠和混合性别双胎妊娠，而后者两者之间没有差异。
双胎妊娠母体血清中 SRY-cffDNA 的水平仅在第三孕期反映胎儿的数量。因此，其作为与双胎妊娠中 SRY-cffDNA 水平改变相关的并发症的诊断工具的使用应在不同的孕周进行评估，特别是在第二孕期。
