Correlation of first-trimester thymus size with chromosomal anomalies

Abstract Objectives The aim of this study was to investigate the correlation between fetal thymus size measured during first-trimester screening and chromosomal anomalies. Methods This study is a retrospective evaluation, in which the anterior-posterior diameter of the thymus in a midsagittal plane was measured in first-trimester ultrasound between 11+0 and 13+6 weeks of gestation in 168 fetuses with chromosomal anomalies (study group) and 593 healthy fetuses (control group). The included cases were subdivided into six groups: (1) trisomy 21, (2) trisomy 18, (3) trisomy 13, (4) Turner syndrome, (5) triploidy and (6) normal controls. Thymus size measurements were adjusted to the week of gestation, which was determined by ultrasound using crown-rump-length (CRL), by calculating a ratio between CRL and thymus size (CRL-thymus-ratio). Each study group was compared with the control group separately. Results Thymus size in fetuses affected by trisomy 18 or trisomy 13 was noticeably smaller compared to the control group (1.4 mm [1.3, 1.5] and 1.3 mm [1.2, 1.4] vs. 1.8 mm [1.6, 2.1]; all p<0.001; respectively). The thymus size of fetuses with trisomy 21 and Turner syndrome did not differ from healthy fetuses. Between the CRL-thymus-ratios of the separate study groups no statistically noticeable differences could be found. Conclusions Fetal thymus size appeared to be smaller in pregnancies affected by trisomy 18 and trisomy 13. The predictive value of fetal thymus size in first-trimester screening should be evaluated prospectively.

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First-trimester screening for trisomy 21 in Denmark: implications for detection and birth rates of trisomy 18 and trisomy 13

Ultrasound in Obstetrics and Gynecology ◽

10.1002/uog.8929 ◽

2011 ◽

Vol 38 (2) ◽

pp. 140-144 ◽

Cited By ~ 35

Author(s):

C. K. Ekelund ◽

O. B. Petersen ◽

L. Skibsted ◽

S. Kjaergaard ◽

I. Vogel ◽

...

Keyword(s):

Trisomy 21 ◽

First Trimester ◽

Trisomy 18 ◽

Trisomy 13 ◽

First Trimester Screening ◽

Birth Rates ◽

Trimester Screening

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Performance of First-Trimester Screening between Gestational Weeks 7 and 13

Clinical Chemistry ◽

10.1373/clinchem.2009.125922 ◽

2009 ◽

Vol 55 (8) ◽

pp. 1564-1567 ◽

Cited By ~ 11

Author(s):

Niels Tørring

Keyword(s):

Blood Sample ◽

Trisomy 21 ◽

Detection Rate ◽

First Trimester ◽

Trisomy 13 ◽

First Trimester Screening ◽

Blood Samples ◽

Before And After ◽

Trimester Screening ◽

Gestational Week

Abstract Background: Screening for fetal chromosome abnormalities in the first trimester includes analysis of the serological markers pregnancy-associated plasma protein A (PAPP-A) and free β human choriogonadotropin (free β hCG). The blood sample is traditionally taken around week 12 of gestation, but the performance of earlier blood sampling is not well documented. Methods: We studied 44 537 singleton pregnancies. Complete first-trimester screening took place between November 2003 and March 2009, and blood samples were taken between 7 weeks + 5 days and 13 weeks + 6 days. Results: Of 120 cases of trisomy 21, 108 were diagnosed in the first-trimester screening (detection rate 90%). When the blood sample was taken before gestational week 10, the detection rate of trisomy 21 was 97% (70 of 72), whereas 80% were detected (38 of 48) after week 10 (χ2 = 0.0035). For trisomy 18, trisomy 13, and triploidy, 65% (13 of 20) were detected before gestational week 10, and 73% (11 of 15) after (not significant). All 6 cases of triploidy before and after gestational week 10 were detected. The screen positive rate and the maternal age were similar before and after week 10 of gestation. Conclusions: Screening for fetal aneuploidy can be performed with good results with the blood sample taken as early as week 7 of gestation. Blood samples taken before gestational week 10 showed a high detection rate of fetal trisomy 21, with no difference in the detection of fetal trisomy 18, trisomy 13, or triploidy.

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Ten Years of Experience with First-Trimester Screening for Fetal Aneuploidy Employing Biochemistry from Gestational Weeks 6+0 to 13+6

Fetal Diagnosis and Therapy ◽

10.1159/000362665 ◽

2014 ◽

Vol 37 (1) ◽

pp. 51-57 ◽

Cited By ~ 4

Author(s):

Niels Tørring ◽

Olav Bjørn Petersen ◽

Niels Uldbjerg

Keyword(s):

Trisomy 21 ◽

High Performance ◽

Protein A ◽

First Trimester ◽

Trisomy 13 ◽

First Trimester Screening ◽

Blood Samples ◽

Fetal Aneuploidy ◽

Trimester Screening ◽

Gestational Week

Objectives: To validate the performance of first-trimester screening for fetal aneuploidy employing blood samples drawn in gestational weeks 6-13. Methods: Prospective combined first-trimester screening for fetal aneuploidy in Denmark was validated in two large datasets: (1) a dataset from the Central Denmark Region including 147,768 pregnancies from October 2003 to October 2013, and (2) a national dataset including 220,739 pregnancies from January 2008 to August 2011. Results: For trisomy 21, the weekly median multiple of the median (MoM) increased from 0.37 in week 6 to 0.70 in week 13 (pregnancy-associated plasma protein-A), and from 0.99 in week 6 to 2.68 in week 13 (free βhCG). The overall detection rate (DR) for fetal trisomy 21 was 91.2%. Employing blood samples from gestational week 9, the DR was 97% (p = 0.05). For fetal trisomy 18, trisomy 13 and triploidy, the overall DRs after first-trimester screening were 79.5, 86 and 85%. In the national dataset, the overall DR for trisomy 21 was 86.3% ranging from 89 (weeks 9 and 10) to 80% (weeks 12 and 13). Conclusion: The results from both datasets show that blood sampling in gestational weeks 9-10 is a robust and high-performance strategy, which can be applied for routine first-trimester screening in clinical practice.

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