Hast to Be Screened Again Due to Her Nt Being Higher Than 2mm
J Res Med Sci. 2015 October; 20(10): 969–973.
Normal reference range of fetal nuchal translucency thickness in pregnant women in the first trimester, one center study
Marzeie Sharifzadeh
Department of Radiology, Isfahan University of Medical Sciences, Isfahan, Iran
Atoosa Adibi
Section of Radiology, Isfahan University of Medical Sciences, Isfahan, Islamic republic of iran
Kimia Kazemi
1School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran
Silva Hovsepian
2Child Growth and Evolution Research Center, Enquiry Institute for Primordial Prevention of Non-Communicable Affliction, Isfahan University of Medical Sciences, Isfahan, Iran
Received 2015 Mar 30; Revised 2015 Aug 22; Accepted 2015 Oct 21.
Abstract
Background:
Considering that establishment of reference value of nuchal translucency (NT)-related to the crown rump length (CRL) during the kickoff trimester will be helpful for determining an appropriate cutoff level for screening of increased NT thickness-related abnormalities, we determined the NT thickness and investigated its relation with dissimilar chromosomal and nonchromosomal abnormalities amidst a large sample size of meaning Iranian women.
Materials and Methods:
In this analytic cross-sectional study, pregnant women who were in their first trimester were enrolled at their antenatal visit. Using an abdominal ultrasonography, the fetal NT thickness of the studied population was measured. Those with increased NT thickness were adamant. The reference value of NT thickness (fifth, 25th, 50th, 75th, and 95th percentiles) inside each 5-mm range of CRL and during the 11th, 12th, and 13th gestational weeks were adamant. The presences of the different chromosomal and nonchromosomal abnormalities were compared in women with dissimilar percentiles of NT thickness who underwent amniocentesis and those who did not.
Results:
1,614 significant women were evaluated. The mean NT thickness was 1.30 ± 0.54 mm. Increased NT thickness >2 mm and >95th percentile according to their gestational age (GA) was detected in 89 (5.v%) and 58 (three.6%) pregnant women. The reference 95th percentile value range for NT was 1.8-2.35 and increased NT thickness according to our obtained values was associated significantly with chromosomal abnormalities.
Conclusion:
The obtained reference range in our studied population was different from that reported for other indigenous groups and it is suggested that using this values are more than favorable for screening of chromosomal abnormalities during the first trimester of pregnancy than the recommended single cutoff value.
Keywords: Crown rump length (CRL), nuchal translucency (NL), reference values
INTRODUCTION
Nuchal translucency (NT) is the normal fluid-filled subcutaneous space between the back of the fetal skin and the overlying skin.[one] NT is visible and can exist measured by ultrasonographic imaging betwixt 11 weeks and xiv weeks gestation.[2] Increased NT is associated with different fetal chromosomal and nonchromosomal abnormalities. At that place is growing evidence that increased NT thickness during the get-go trimester of pregnancy in a chromosomally normal fetus is associated with numerous fetal structural abnormalities, genetic syndromes, eye defects, and poor perinatal outcomes such equally miscarriage and intrauterine death.[3,4,5]
The first definition for increased NT was a measure out >95thursday percentile for a given crown rump length (CRL) and a NT value of 2.5-three mm, which was reported as a normal range for the marking. Recently, some studies indicated that NT >99th percentile or NT value that exceeds of three.5 mm are associated with the most common adverse outcomes.[6,seven]
The utility of NT as a sensitive and noninvasive ultrasonographic marking for screening and detection of aneuploidies and major structural anomalies in modern obstetrical practice has been demonstrated recently. Its apply as a new screening method for the mentioned purposes has been developed in many developed countries.[viii,ix,x]
Since the introduction of NT thickness, several studies worldwide have adamant the normal range of NT in different populations. The results were different regarding the normative value of NT. One of the explanations for the reported great variety of NT thickness range is ethnic variation.[11,12,13,14,fifteen] Yet, in that location are withal controversies regarding the function of ethnicity on the value of NT. Some reported a meaning role of ethnicity in this regard, whereas others did not support the association.[16,17] However, recently the institution of reference value for NT in unlike populations was performed. It is suggested that ethnic and region-specific reference value of NT could have a significant affect on its screening efficacy and using a unmarried cutoff for fetal NT could not be an appropriate tool in this field.[18]
So considering that establishment of reference value of NT related to the CRL during the first trimester will be helpful for determining an advisable cutoff level for screening of increased NT thickness-related abnormalities and the presence of few reports in this field among the Iranian population, in this study we determined the reference values of NT thickness among Isfahani significant women to evaluate the role of ethnicity on the normative value of NT as well as the association of increased NT thickness with chromosomal and nonchromosomal abnormalities during the first trimester.
MATERIALS AND METHODS
In this analytic cross-exclusive study, pregnant women referred to a private radiology center for ultrsonographic assessment during the antenatal visit in their offset trimester were enrolled. The study was performed from January 2013 to December 2013 in Isfahan, Isfahan Province, Iran.
The protocol of the report was canonical past the Regional Ideals Committee of Isfahan University of Medical Sciences.
Pregnant women with gestational age (GA) of 11-13 weeks and 6 days and/or CRL 45-84 mm were included.
The pregnant women were selected by the consecutive method. Those who did not agree to have the ultrasonography performed, with multiple pregnancies, fetal malformation, and those with inappropriate cooperation were excluded. Written informed consent was obtained from all the selected participants. The selected pregnant women underwent abdominal ultrasonography. The sonography was performed past an expert radiologist. The fetal NT thickness of the studied population was measured.
Those with NT thickness of 2 mm were considered as women with increased NT thickness.[nineteen]
The hateful of CRL and GA were compared in women with and without increased NT thickness.
The reference value of NT thickness (vth, 25th, lth, 75th, and 95th percentiles) within each 5-mm range of CRL and during the xith, 12th, and 13th gestational weeks were determined.
Women with NT thickness of >95th percentile were adamant. The women were followed up and fetal outcomes were evaluated by the neonatologists at birth. The presence of different chromosomal abnormalities besides as nonchromosomal abnormalities including cardiac malformation, genitourinary or renal abnormalities, diaphragmatic hernia, spontaneous miscarriage, and intrauterine fetal death (IUFD) were compared in women with different percentiles of NT thickness who underwent amniocentesis and those who did not.
Ultrasonographic measurements
The ultrasonographic measurements were performed in pregnant women in a supine position.
Fetal CRL and NT thickness measurements were performed by transabdominal ultrsonography using a multi fz: 3.5 MHz tranduser (GE Volusun 730). The measurement was performed based on the criteria recommended past the Fetal Medicine Foundation (FMF).[20] According to the criteria, the fetus should be in a neutral position, with the head aligned with the spine in a style that fetus occupied at least 75% of the image. NT was defined as the black area between the inner skin outlines repeat and the outer border of the soft tissue overlying the cervical spine.
The maximal thickness of the black area was measured with caliper placed on the inner borders of the NT space, perpendicular to the long axis of the fetus when a sagittal section with a neutral position of the fetus was obtained. The measurements were recorded to the nearest 0.one-mm interval. At to the lowest degree iii NK measurements were taken and the largest was recorded.
CRL was measured at the aforementioned time and recorded.
Statistical analysis
Data were analyzed using Statistical Package for the Social Sciences (SPSS) version 21 (SPSS Inc., Chicago, IL, USA). Using regression equation, the expected 5th, 25th, fiftyth, 75th, and 5thursday percentile values of NT thickness co-ordinate to the CRL categories of CRL (5-mm interval) and GA (11thursday, 12th, and thirteenthursday weeks) were obtained. Quantitive and qualitative values were compared using the t-test and chi-square test, respectively. P value of <0.05 was considered to be statistically significant.
RESULTS
During this study, i,614 meaning women were evaluated. Among the studied pregnant women 382 (23.7%), 871 (54.0%), and 361 (22.4) were in the 11th, 12th, and 13th gestational calendar week. The mean of GA, CRL, and NT thickness in the studied population were 12.46 ± 0.62 weeks, 59.35 ± eight.35 mm, and 1.xxx ± 0.54 mm, respectively. Pearson correlation test indicated that there was a significant positive correlation between NT and CRL (r = 0.238, P < 0.001), NT and GA (r = 0.24, P < 0.001 and GA) and CRL (r = 0.8, P < 0.001).
Increased NT thickness (NT >2 mm) was detected in 89 (5.five%) significant women. The hateful of CRL and GA in pregnant women with normal and increased NT thickness are presented in Table ane.
Table ane
Mean ± SD of CRL and GA in pregnant women with normal and increased NT thickness
The expected 5thursday, 25th, lth, 75th, and 95th percentile values of NT thickness to CRL and GA are listed in Tables 2 and 3. Using the obtained reference value of NT, 58 (iii.6%) pregnant women were determined as those with NT thickness >95th percentile according to their GA. During follow-up, 31/58 (53.4%) underwent amniocentesis. Distribution of chromosomal and nonchromosomal abnormalities in meaning women with NT thickness >95th percentile according to their GA in total and amongst those with and without amniocentesis are presented in Table 4. Frequency of chromosomal abnormalities were significantly higher in those pregnant women with increased NT thickness who underwent the amniocentesis procedure (P = 0.001). The frequency of different nonchromosomal abnormalities were non significantly different betwixt the two studied groups (P > 0.05).
Tabular array 2
The expected 5thursday, 25th, fiftyth, 75th, and 95thursday percentile values of NT thickness (mm) to CRL
Table 3
The expected fiveth, 25th, 50th, 75th, and 95th percentile values of NT thickness (mm) to gestational age (GA)
Table iv
Distribution of chromosomal and nonchromosomal abnormalities in pregnant women with NT thickness >95th percentile according to their GA in total and among those with and without amniocentesis
Discussion
In this study, we determined the reference values of NT thickness among meaning Isfahani women to evaluate the role of ethnicity on the normative value of NT as well as the association of increased NT thickness with chromosomal and nonchromosomal abnormalities during the first trimester. The results indicated that the reference 95th percentile value range for NT was one.8-ii.35 and increased NT thickness co-ordinate to our obtained values was associated significantly with chromosomal abnormalities.
Several reports from unlike parts of the worlds and Iran accept demonstrated the utility of NK measurement for screening dissimilar chromosomal and nonchromosomal abnormalities.[20,21,22,23]
Nearly of the studies have used the recommended definition for NT thickness by the FMF (i.e., 2.5-3 mm),[6] whereas recent studies reported that using NT thickness as a continuous variable was more than advisable than using a single cutoff value for the fetal NT and consequently, the outcomes of its increased values and screening programs.[18] So, establishment of reference values of NT accept been developed in different regions and ethnic groups worldwide.
Though there were studies in Islamic republic of iran, which investigated the association between increased NT value and Down's syndrome[22] and adverse pregnancy upshot including miscarriage, fetal loss, and fetal abnormalities,[23] in that location was not any study, which reported the normative value of NT thickness for the Iranian population. So, this study was designed to determine the ethnic specific reference value of NT thickness for significant Iranian women. Our results indicated that the median NT thicknesses for a CRL between 45 mm and 80 mm ranged from one.00 to 1.65 mm, and the 95th percentiles ranged from 1.8 to 2.35 mm. The median NT thickness for GA were 1.0 mm, one.ii mm, and 1.four mm for gestational age of 11 weeks, 12 weeks, and 13 weeks, respectively, and the 95th percentiles of NT thickness were ane.8, 1.9, and two.2 for gestational historic period of 11 weeks, 12 weeks, and 13 weeks, respectively.
The distribution of the NT thickness for CRL has been reported in many studies. The median NT thicknesses has been reported to be ane.ii-1.ix mm, 1.22-2.ten mm, and 1.nineteen-one.73 mm for a CRL between 45 mm and 80 mm in Japan, Korea, and Brazil, respectively.[11,12,thirteen] Our reported median value was lower than the other reports.
The 95th NT thickness percentiles take been reported to be 2.ane-three.ii mm, 2.14-2.iii mm, 1.57-2.x mm, 1.00-ii.xc mm, and 1.84-two.35 mm for a CRL between 45 mm and lxxx mm in Japan, Korea, Brazil, Thailand, and Communist china, respectively.[11,12,thirteen,14,15] Our results were like to the reported reference value range of Brazil.[13] Although in that location was no study from the Eastern Mediterranean region in this field, the values were not similar to the values reported from the Asian countries.
Reported variations in the index measurements in the unlike studies might have been due to factors such as radiologist experience, quality of the ultrasound, method of measurement, and an inappropriate fetal and nuchal cord position. In addition, equally mentioned past Kor-anantaku et al. in Thailand some investigators have considered the average of 2 or three measurements of NT thickness, whereas others considered the largest measurement.[14]
There are controversial reports regarding the bear upon of ethnicity on NT thickness values and its utility for screening. Thilaganathan et al. take investigated the possible role of ethnicity on NT screening and concluded that the reported differences could not have a pregnant affect in this regard.[24] Many other studies have as well showed that ethnic differences in NT measurements are not clinically pregnant, specially when it used for screening of Down syndrome.[17,24,25] All the same, information technology seems that using ethnic-specific reference values of NT thickness could help u.s.a. in the first trimester screening programs mainly for chromosomal aberration, specially when they are integrated with other ultrasonographic and biochemical measurements.
In this study using the unmarried cutoff value of two mm, five.v% of the studied pregnant women were considered to have high-risk pregnancy and after using our obtained reference value the rate decreased to 3.6%. Thus, it seems that using normative values of NT thickness is more useful for the starting time trimester screening and it could optimize the screening results by reducing imitation positive cases.
In addition, there was significant clan between performing the amniocentesis procedure and detection of chromosomal abnormalities among women with increased NT thickness.
The reward of the current study was a larger sample size of enrolled pregnant women.
The limitation of the electric current study was that we did not decide the sex-specific reference value of 95th percentiles of NT and its association with both chromosomal and nonchromosomal abnormalities. Nosotros followed upwards only pregnant women with increased NT thickness and did not decide the frequency of the mentioned abnormalities in pregnant women with normal NT. It was due to the reason that follow-up of that large a sample size was not assessable in the framework of the current study. In addition, we enrolled the patients who were referred to a single referral radiologic eye, which could not be a representative sample of the whole population. Information technology is suggested that the large sample size of the studied population could partially convalesce the abovementioned limitation.
Further, the planning of further studies that as well determine the 99th percentile values of NT thickness is recommended considering recent studies demonstrated that chromosomal and nonchromosomal abnormalities are mainly associated with the 99th percentile value of NT thickness.[7]
The results of our study indicated the reference value of NT thickness in a large sample size of Isfahani pregnant women. The obtained reference range in our studied population was different from that reported for other ethnic groups and it is suggested that using this values are more favorable for screening of chromosomal abnormalities during the beginning trimester of pregnancy than the recommended unmarried cutoff value. The relation betwixt increased NT thicknesses with chromosomal abnormalities besides confirms its utility. The results of the electric current study could be used every bit baseline data for other follow-upwards studies and designing first trimester screening programs.
Fiscal support and sponsorship
Zero.
Conflicts of interest
There are no conflicts of interest.
AUTHOR'S CONTRIBUTION
All authors contributed in the conception of the work, conducting the study, revising the draft, blessing of the last version of the manuscript, and agreed for all aspects of the work.
Acknowledgments
The study was supported by Isfahan University of Medical Sciences (research project number; 393486).
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Source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4746871/
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