Nuchal translucency measurement and pregnancy outcome after assisted conception versus spontaneously conceived twins

Department of Obstetrics and Gynecology, Assaf Harofe Medical Center, Sackler Faculty of Medicine, Tel Aviv University, Zerifin 70300, Israel.
Human Reproduction (Impact Factor: 4.57). 10/2001; 16(9):1999-2004.
Source: PubMed


Nuchal translucency (NT) measurement for Down's syndrome screening or detecting various fetal anomalies is a reliable sonographic marker. This study evaluates the contribution of NT screening in spontaneously conceived and assisted conception twin pregnancies.
Maternal age at measurement, chorionicity, ultrasound features, karyotype results and pregnancy outcome were recorded prospectively and compared in 83 assisted reproduction treatment and 91 spontaneously conceived twins. Pregnancy outcome was evaluated according to maternal age, method of conception, NT data and chorionicity. NT measurements (> or =95 centiles of the normal range) were considered screen-positive and mid-pregnancy fetal karyotyping was advised. Complicated pregnancy outcome, which could be signalled by increased NT, was defined as either chromosomal abnormalities, severe structural defects or fetal demise. Based on NT measurements, 16 fetuses (4.6%) were found to be screen-positive. Five of them had chromosomal aneuploidy and selective termination was performed. The parents also opted for this procedure in another five fetuses because of major structural abnormality diagnosed during NT assessment. No other chromosomal or major fetal abnormality were found post-natally. Although no difference was found in NT, crown-rump length and maternal age between spontaneous and assisted reproduction technology twin pregnancies, the former group had a significantly higher rate of screen-positive results (7 versus 2%, P = 0.047), amniocentesis uptake (33 versus 22%, P = 0.014), monochorionic twining (32 versus 4%, P = 0.001) and complicated pregnancy outcome (11 versus 5%, P = 0.02).
The present study confirms that first trimester target scanning can improve outcome by early detection and management of cases with an anomalous co-twin. It also identifies some differences between spontaneously and artificially conceived twin pregnancies in relation to this area of testing.

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Available from: Eric Jauniaux, Feb 09, 2014
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    • "In twin pregnancies, effective screening for chromosomal abnormalities is provided by a combination of maternal age and fetal NT thickness (Pandya et al., 1995b; Sebire et al., 1996a, 1996b; Maymon et al., 2001). The performance of screening can be improved by the addition of maternal serum biochemistry, but appropriate adjustments are needed for chorionicity (Sepulveda, et al., 1996). "
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    ABSTRACT: Effective screening for major aneuploidies can be provided in the first trimester of pregnancy. Screening by a combination of fetal nuchal translucency and maternal serum free-β-human chorionic gonadotrophin and pregnancy-associated plasma protein-A can identify about 90% of fetuses with trisomy 21 and other major aneuploidies for a false-positive rate of 5%. Improvement in the performance of first-trimester screening can be achieved by firstly, inclusion in the ultrasound examination assessment of the nasal bone and flow in the ductus venosus, hepatic artery and across the tricuspid valve, and secondly, carrying out the biochemical test at 9 to 10 weeks and the ultrasound scan at 12 weeks.
    Prenatal Diagnosis 01/2011; 31(1):7-15. DOI:10.1002/pd.2637 · 3.27 Impact Factor
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    • "There have been suggestions that the NT thickness is higher in MC twins than DC, possibly due to twin–twin transfusion (Sebire et al., 1996; Monni et al., 2000). However, others have found no significant differences according to the chorionicity in the screen-positive rate based on the NT (Maymon et al., 2001) or the median NT (Linskens et al., 2009). In a small series of 30 twins resulting from IVF or ICSI, the median NT was 10% lower than in 150 spontaneous twins, although not statistically significant (Orlandi et al., 2002). "
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    ABSTRACT: The objective of this study was to describe and illustrate a method for calculating fetus-specific Down syndrome risk in twins, allowing for between-fetus nuchal translucency (NT) correlation. The between-fetus correlation coefficient of log NT, in multiples of the median, was estimated from a series of 325 unaffected twins after adjustment for sonographer bias. A bivariate log Gaussian model was used to calculate likelihood ratios for discordant and concordant Down syndrome. Applying these to the prior maternal age-specific risk yielded risks in monozygous and dizygous twins. The weighted average risk was then computed with weights relating to chorionicity, gender, assisted reproduction and ethnicity. The method was illustrated using examples. The correlation coefficient in unaffected pregnancies was 0.45 (P < 0.0001) and estimated to be 0.12 and 0.04 in discordant and concordant twins, respectively. The examples showed very large differences in the risks obtained when the extent of correlation in NT between fetuses is taken into account and when the measurements are treated as independent. Fetus-specific Down syndrome risks in twins should be calculated using its own NT value as well as that of the co-twin.
    Prenatal Diagnosis 09/2010; 30(9):827-33. DOI:10.1002/pd.2557 · 3.27 Impact Factor
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    • "However, fetal NT values were significantly lower in monochorionic than in dichorionic twin pregnancies (Table 8); the latter is consistent with the results of Gonce et al. (2005). Other studies found no differences in fetal NT measurements between twins and singletons (Mashiach et al., 2004) or between mono-and dichorionic twin pregnancies (Maymon et al., 2001). "
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    ABSTRACT: To establish normative values and distribution parameters of first-trimester screening markers, namely, fetal nuchal translucency (NT), maternal serum free β-human chorionic gonadotrophin (β-hCG) and pregnancy-associated plasma protein-A (PAPP-A), at 10 to 13+6 weeks of gestation in Saudi women and to evaluate the effect of co-variables including maternal body weight, gravidity, parity, fetal gender, twin pregnancy, smoking and ethnicity on these markers. A cohort of Saudi women (first cohort n = 1616) with singleton pregnancies prospectively participated in the present study, and fetal NT together with maternal serum free β-hCG and PAPP-A were determined at 10 to 13+6 weeks of gestation. The distribution of gestational age-independent multiples of the median (MoM) of the parameters was defined and normative values were established, and correction for maternal body weight was made accordingly. The influence of various co-variables was examined using the data collected from the first and the second (n = 1849) cohorts of women and 62 twin pregnancies, and compared with other studies. All markers exhibited log-normally distributed MoMs. Gestational age-independent normative values were established. Maternal body weight was corrected, particularly for maternal free β-hCG and PAPP-A using standard methods. Fetal NT showed a negative relationship with increasing gravidity (r = −0.296) or parity (r = −0.311), whereas both free β-hCG and PAPP-A exhibited a significant positive relationship. There was a significant increase in the MoM of free β-hCG in female fetuses. Smoking decreased MoM values of free β-hCG (by 14.6%; P < 0.01) and PAPP-A (by 18.8%; P < 0.001). Twin pregnancy showed significant increases in MoM values of free β-hCG (by 1.87-fold) and PAPP-A (by 2.24-fold), with no significant changes in fetal NT MoM values. Fetal NT MoM values were lower in Africans and Asians but higher in Orientals, as compared to Saudi women (P < 0.05; in each case). MoM values (body weight-corrected) of free β-hCG were 25.2% higher in Africans and 19.4% higher in Orientals but 6.8% lower in other Arabian and Asian (by 5.8%) women as compared to Saudi women (P < 0.05; in each case). The normative values and distribution parameters for fetal NT, maternal serum free β-hCG and PAPP-A were established in Saudi singleton pregnancies, the maternal body weight together with smoking, twin pregnancy and ethnicity being important first-trimester screening co-variables. Gravidity, parity and fetal gender are also considered to influence one or more of the first-trimester markers examined. Copyright
    Prenatal Diagnosis 04/2007; 27(4):303-11. DOI:10.1002/pd.1661 · 3.27 Impact Factor
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