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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    • "Determination of chorionicity is based on the appearance with ultrasound of an extension of placental tissue into the base of the intertwine membrane, forming the lambda sign (Sepulveda et al., 1996Sepulveda et al., , 1997). When severe abnormalities are diagnosed in a dichorionic twin, selective feticide is suggested (Maymon et al., 2001 ). As generally accepted, we base prenatal ultrasonographic diagnosis of anencephaly late in the first or early in the second trimester of pregnancy on detection of an absent cranial vault and cerebral hemispheres (Campbell et al., 1972). "
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    ABSTRACT: The incidence rates of anterior neural tube defects, anencephaly and encephalocele appear increased among twins compared with singletons. The current study aimed to evaluate whether the etiology of this phenomenon is related to twinning, assisted reproductive technology (ART), or both. The study cohort consisted of parturient women who were referred to our ultrasonography unit between January 1998 and December 2009 due to suspicion of severe fetal abnormality. The study cohort was divided into two subgroups based on mode of conception: spontaneous and ART (including IVF and ICSI). The subgroups were further subdivided into singleton and multiple pregnancies. We also compared pregnancies diagnosed with anencephaly in the study group to all live births in the Department of Obstetrics and Gynecology. Anencephaly was diagnosed in 43 fetuses out of 1154 (3.7%) pregnancies diagnosed with severe fetal anomaly. Anencephaly was diagnosed in 9 out of 78 twin pregnancies (11.5%); of these, 8 of 45 (17.8%) were ART conceived and 1 of 33 (3%) spontaneously conceived. A significant correlation was found between twinning and anencephaly, with an odds ratio (OR) of 3.4 [confidence interval (CI) = 1.3-8.9, P= 0.011], while no significant correlation was found between ART and anencephaly. A significant correlation was found between anencephaly and the combination of ART conception and twinning (OR of 6.6, CI = 2.8-15.3, P< 0.01). Analyzing the distribution of pregnancies diagnosed with anencephaly in the study group compared with the total number of live births in the department revealed a significant correlation between twinning and anencephaly, with an OR of 11.4 (CI = 4.9-26.5, P< 0.01), with no significant correlation between ART and anencephaly. Among all live births, a significant correlation was found between anencephaly and the combination of ART conception and twinning (OR of 24.6, CI = 11.4-53.2, P< 0.01). Our data suggest that twin pregnancies conceived by ART constitute a high-risk group for anencephaly, due to a possible synergistic effect of twinning and ART.
    Preview · Article · Dec 2011 · Human Reproduction
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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.
    Preview · Article · Jan 2011 · Prenatal Diagnosis
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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.
    Full-text · Article · Sep 2010 · Prenatal Diagnosis
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