Ethnic-specific reference range affects the efficacy of quadruple test as a universal screening for Down syndrome in a developing country.

OBJECTIVE: To evaluate the efficacy of the quadruple test for potential use as a Thai national policy for Down syndrome (DS) screening and establish an accurate equation for risk estimation of Down syndrome based on gestational age, weight and the ethnic-specific reference range of our population. METHODS: A prospective study was conducted on singleton pregnancies at 14 to 21 weeks of gestation to evaluate the efficacy of quadruple DS screening using the automatically calculated Western European descent factor (WF) in our population and the impact of screening using a specific Thai ethnic factor as well as to establish an equation for the risk estimation of DS based on gestational age, weight and a local Thai ethnic factor to correct for the impact of ethnic factor on the screening efficacy. RESULTS: Of a total of 5,515 women, 12 cases of DS and 8 cases of other aneuploidies were found. The detection rate, false positive rate and specificity were 75.0%, 9.1% and 90.9%, respectively, by automatic calculation with the widely used WF; the screening efficacy was lower when used in Asian populations than in other studies. The best-fitted regression equation of serum quadruple screening of AFP, free ß-hCG, uE3 and inhibin A was established by adjustment for gestational age (GA) in days, maternal weight and our Thai-specific ethnic reference range which was created for this study. Calculations with our Thai-specific ethnic model gave a better detection rate of 83.3%, a false positive rate of 9.6% and specificity of 90.4%. CONCLUSION: The serum quadruple test had a lower detection rate than expected when the risk estimation was based on the WF reference range. The serum quadruple test using WF had significantly different levels when corrected with our ethnic-specific factor. Using our local ethnic specific model could increase the detection rate of DS screening in Thailand with a minimal increase in false positive rates. Our findings indicate that DS screening should be adjusted with an appropriate individual ethnic factor when used for national screening.

Calcium Consumption During Pregnancy: A Multicenter Study in a Middle-Income Country in Southeast Asia.

OBJECTIVE: To perform a cross-sectional observational study of calcium consumption among pregnant women from multicenter tertiary care hospitals in the middle-income country in Southeast Asia. STUDY DESIGN: A cross-sectional observational study. SETTING: The study was conducted in four geographical regions (northern, northeastern, southern, and central) of Thailand. Five participating hospitals consisted of one university hospital in each region and one additional tertiary care hospital in the central region. MATERIALS AND METHODS: A cross-sectional study was performed nationwide from 1st November 2017 to 31st January 2019. All singleton aged 19-40 years were included. Exclusion criteria were any conditions that influenced calcium-containing food consumption. Dietary intake self-records immediately after eating for two working days and one holiday were analyzed via INMUCAL-NV3.0 dietary program. RESULTS: The 1549 records were obtained. The mean age was 29 ± 5.7 years. Most participants were primigravida (48.6%). The average gestational age was 20.6 ± 8.8 weeks. Mean calcium consumption was 602.4 mg/day (95% CI; 589.2615.6 mg/day) mg/dL. Inadequate calcium consumption prevalence based on the Thai dietary reference intake (less than 800 mg/day) and US Institute of Medicine (less than 1000 mg/day) were 82.0% and 93.4%, respectively. CONCLUSION: The mean calcium consumption among pregnant women in the middle-income country in Southeast Asia was 602.4 mg/day (95% CI 589.2-615.6 mg/day). Inadequate calcium consumption of Thai pregnant women prevalence was 82.0% and 93.4% according to Thai dietary reference intake in pregnancy and the US Institute of Medicine.

Distribution of uterocervical angles in the second trimester of pregnant women at low risk for preterm delivery.

The uterocervical angle (UCA) has recently been studied as a parameter to identify women at risk for spontaneous preterm birth (sPTB). This study aimed to investigate the distribution of UCA values by transvaginal sonography (TVS) in the second trimester of women at low risk for sPTB. TVS was performed in 450 low-risk pregnant women at gestational age (GA) 160/7-240/7 weeks. The UCA distribution by GA was visualised using a scatter plot. The range of UCA values and their relationship with GA were assessed using quantile regression analysis. p < .05 was considered statistically significant. A total of 242 participants with anteflexed uterus, no history of caesarean section and term delivery were analysed. The normal range of UCA (5th and 95th percentiles) was from 63.0 degrees (95% CI, 53.1-72.9) to 148.8 degrees (95% CI, 139.5-158.0) with no significant changes during this GA period (-0.3 degrees per week, p = .757).Impact statementWhat is already known on this subject? Spontaneous preterm birth (sPTB) is a major problem in obstetrics. A screening strategy using history of sPTB and cervical length (CL) measurement is the current standard to identify women at risk for sPTB and provide adequate prevention. However, a third of women who are identified as low risk go on to have sPTB, so a better means needs to be found to more reliably identify women at risk. Various studies have found that a wide uterocervical angle (UCA) was associated with sPTB, and thus the UCA has been proposed as a potential sPTB screening parameter. However, to date there is a lack of prospective studies evaluating this proposal, and no consensus about the proper gestational age to perform UCA measurements to identify women at risk of sPTB.What do the results of this study add? This study reports the distribution of UCA at the GA of 160/7-240/7 weeks of low-risk singleton pregnancy women who delivered at term. The mid-90% values ranged from 63.0 degrees to 148.8 degrees with no significant differences in this GA period.What are the implications of these findings for clinical practice and/or further research? Because of the wide range of UCA values at GA 160/7-240/7 weeks, more studies regarding UCA values in various gestational ages are required to fully understand the trend of UCA values along pregnancy and confirm whether or not the UCA would be a useful parameter for sPTB prediction and if so at what gestational age it would have to be assessed.

Uterocervical angle measurement for preterm birth prediction in singleton pregnant women with no history of preterm birth and normal cervical length: A prospective cohort study.

OBJECTIVE: To evaluate the ability of second trimester uterocervical angle (UCA) to predict spontaneous preterm birth (sPTB) in low-risk singleton pregnant women. STUDY DESIGN: Transvaginal sonographies were performed in the second trimester of 450 singleton pregnant women with no history of sPTB and no history of second trimester miscarriage with normal cervical length (CL) who attended antenatal care at Songklanagarind Hospital, a tertiary teaching hospital in southern Thailand. Gestational ages at delivery were recorded then the UCA values were evaluated according to sPTB occurrence. The differences in mean values of UCA between sPTB and full-term groups were evaluated using t-test. A receiver operating characteristics (ROC) curve was used to assess the ability of UCA to predict sPTB. RESULTS: After excluding women with unknown pregnancy outcomes or missing UCA images, the sPTB rate was 34/421 (8.1 %). In women with anteflexed uterus, the mean UCA value was wider in the sPTB group compared to those with term birth if the measurements were performed at GA 19.5-24 weeks (sPTB group, 123.4°vs controls, 104.3°; P = 0.017). The ROC curve showed an area under the curve (AUC) of 0.7045. The optimal UCA cut-off value was ≥110 degrees, which gave a sensitivity of 83.3 % and a specificity of 61.2 %. The positive predictive value (PPV) was 16.7 %, negative predictive value (NPV) 97.5 %, positive likelihood ratio (LR+) 2.2 and negative likelihood ratio (LR-) 0.3. CONCLUSION: The UCA in the second trimester is not a good predictor of sPTB in low risk pregnant women.

Comparison of reliability between uterocervical angle and cervical length measurements by various experienced operators using transvaginal ultrasound.

Purpose: To compare the reliability between uterocervical angle (UCA) and cervical length (CL) measurements by various experienced operators.Methods: Transvaginal ultrasonographies (TVS) were performed in 102 pregnant women between 16°/7-24°/7 gestational weeks by different levels of experienced operators. For both CL and UCA measurements, intraobserver variability was assessed for each operator by examining the range between maximum and minimum measurements in each participant, compared to the mean of all three measurements. Interobserver variabilities were explored using Bland-Altman analysis. Intraclass correlation coefficients were used for both intraobserver and interobserver reliability.Results: For intraobserver variability of the UCA, the ranges between maximum and minimum UCA measurements in operator 1 and 3 were 1.5º-34º and 2º-36º (n = 51), and in operators 2 and 3 were 0º-61º and 1º-25º (n = 51). Intraclass correlation coefficients (ICC) for intraobserver reliability were 0.90 for operator 1, 0.67 for operator 2 and 0.93 for operator 3. For interobserver variability of the UCA, the limits of agreement for mean UCA were -37.53º-38.41º and -36.27º-26.17º, and for maximum UCA were -39.47º-41.38º and -44.24º-22.9º in comparisons between operators 1 and 3, and operator 2 and 3, respectively. Intraclass correlation coefficients for mean UCA were 0.73 and 0.74, and for maximum UCA were 0.71 and 0.67 in comparisons between operators 1 and 3, and operator 2 and 3, respectively.Conclusions: The UCA measurements had a higher intra- and interobserver reliabilities than the CL measurements.

Comparison of transabdominal and transvaginal sonography in the diagnosis of placenta previa.

PURPOSE: To compare the accuracies of transabdominal sonography (TAS) and transvaginal sonography (TVS) in the diagnosis of placenta previa. METHODS: A prospective, cross-sectional study was conducted at a university hospital. Both TAS and TVS were performed on 81 pregnant women with a suspicion of placenta previa in the third trimester. The final diagnosis was confirmed at delivery. The agreement between the two ultrasound methods and the parameters of each method were calculated. RESULTS: Fifty-eight percent of the women had a placenta previa. The sensitivities of TAS and TVS were 86% (95% CI 78-94%) and 95% (95% CI 91-100%), respectively (p= 0.2). The specificity of both methods was 93% (95 CI 88-99%), and the overall accuracies of TAS and TVS were 89% (95% CI 82-96%) and 94% (95% CI 89-100%), respectively. When TAS was followed by TVS, 23% of the previous diagnoses were changed. The agreement between both methods was good (Kappa value = 0.7, 95%CI 0.55-0.86). CONCLUSIONS: For the diagnosis of placenta previa, TAS showed a high sensitivity and specificity, which were comparable to those of TVS.

Time Interval Measurements of the Ductus Venosus During the Early Second Trimester of Pregnancy: Reference Ranges and Clinical Application.

OBJECTIVES: The aims of this study were to construct reference ranges for the time interval parameters of the ductus venosus during the early second trimester of pregnancy and to demonstrate the clinical utility in various fetal disorders. METHODS: The ductus venosus Doppler measurements of 331 healthy fetuses between 15 and 22 weeks' gestation were analyzed. The systolic time and diastolic time were subdivided into the systolic acceleration time, systolic deceleration time, diastolic acceleration time, and diastolic deceleration time. The median, 5th, and 95th regression lines for each variable were determined according to gestational age. The ductus venosus time interval parameters in cases of fetoplacental abnormalities were calculated and plotted against the reference ranges. RESULTS: With advancing gestation, the systolic acceleration time and total systolic time increased significantly (P < .001). In contrast to the systolic phase, the diastolic deceleration time decreased significantly during the early second trimester of pregnancy (P = .023). The systolic deceleration time, diastolic acceleration time, and diastolic time were relatively constant. Fetuses with tricuspid insufficiency, twin-twin transfusion syndrome, intrauterine fetal growth restriction, and anemia had abnormal ductus venosus times with different patterns. CONCLUSIONS: Predicted normal reference ranges for time interval variables in relation to gestational age were established. These could be helpful for assessing fetal cardiovascular function during the early second trimester of pregnancy.

Normative weight-adjusted models for the median levels of first trimester serum biomarkers for trisomy 21 screening in a specific ethnicity.

OBJECTIVE: To establish normative weight-adjusted models for the median levels of first trimester serum biomarkers for trisomy 21 screening in southern Thai women, and to compare these reference levels with Caucasian-specific and northern Thai models. METHODS: A cross-sectional study was conducted in 1,150 normal singleton pregnancy women to determine serum pregnancy-associated plasma protein-A (PAPP-A) and free ß-human chorionic gonadotropin (ß-hCG) concentrations in women from southern Thailand. The predicted median values were compared with published equations for Caucasians and northern Thai women. RESULTS: The best-fitting regression equations for the expected median serum levels of PAPP-A (mIU/L) and free ß- hCG (ng/mL) according to maternal weight (Wt in kg) and gestational age (GA in days) were: [Formula: see text] and [Formula: see text] Both equations were selected with a statistically significant contribution (p< 0.05). Compared with the Caucasian model, the median values of PAPP-A were higher and the median values of free ß-hCG were lower in the southern Thai women. And compared with the northern Thai models, the median values of both biomarkers were lower in southern Thai women. CONCLUSION: The study has successfully developed maternal-weight- and gestational-age-adjusted median normative models to convert the PAPP-A and free ß-hCG levels into their Multiple of Median equivalents in southern Thai women. These models confirmed ethnic differences.

Agreement of three interpretation systems of intrapartum foetal heart rate monitoring by different levels of physicians.

A prospective study was conducted in centre in Southern Thailand, to evaluate agreement in EFM interpretation among various physicians in order to find out the most practical system for daily use. We found strong agreement of very normal FHR tracings among the FIGO, NICHD 3-tier and 5-tier systems. The NICHD 3-tier was more compatible with the FIGO system than 5-tier system. Overall inter-observer agreement was moderate for the NICHD 3-tier system while inter-observer agreement of 5-tier system was fair also the intra-observer agreement was higher in the NICHD 3-tier system. So the 3-tier systems are more suitable than the 5-tier system in general obstetric practice. Impact statement What is already known on this subject: The 3-tier and 5-tier systems were widely used in general obstetrics practice. What the results of this study add: The inter- and intra-observer agreement of NICHD 3-tier system was higher than the 5-tier system. What the implications are of these findings for clinical practice and/or further research: The 3-tier systems were more suitable than the 5-tier systems in general obstetrics practice.

Complete hydatidiform mole with co-existing fetus: Predictors of live birth.

Multiple gestation consisting of complete hydatidiform mole with co-existing fetus (CHMCF) is unusual. From our institution, we reported two cases with unfavorable obstetric consequences. The recommendation for antenatal management is still not distinctly determined. Therefore, the aim of this article was to review the literature according to the predictors of infant survival and to develop a management guidance for pregnancy with CHMCF. Between January 1, 1993 and May 31, 2016, 12 case series and 89 case reports comprising of 204 pregnant women were identified. The pregnancies successfully delivered 78 live births (37.86%). For clinical symptoms, pregnant women with antenatal complications, including pregnancy-induced hypertension (PIH), hyperthyroidism (HTD) and hyperemesis gravidarum (HG), significantly developed adverse perinatal events. Low hCG blood level was the best predictor of fetal survival (P=0.006). We developed a model using logistic regression analysis which was enhanced by including an hCG cut-off level of 400,000mIU/mL. On the basis of our intensive review, we suggest that the patient with CHMCF without antenatal obstetric problems especially PIH, HTD and HG together with initial serum hCG level less than 400,000mIU/mL is a good candidate for pregnancy continuation and reaching fetal viability.

A population-based study of prevalence of Down syndrome in Southern Thailand.

BACKGROUND: Down syndrome (DS) is the most common chromosomal disorder that causes mental retardation. In 2009, a population-based birth defects study was implemented in three provinces in southern Thailand. This study aimed to determine the prevalence of DS in the studied regions, and the proportion of DS fetuses detected by prenatal screening. METHODS: Data were obtained from a population-based surveillance study undertaken during 2009-2013. Entries in the birth defects registry included live births, stillbirths after 24 weeks gestational age, and terminations of pregnancy following prenatal diagnosis. Infants with clinical characteristics of DS had a chromosomal study to make a definite diagnosis. RESULTS: Of the total 186 393 births recorded during the study period, 226 DS cases were listed, giving a prevalence of 1.21 per 1000 births [95% confidence interval (CI) 1.05-1.37]. The median maternal age was 36.5 years with a percentage of maternal age ≥35 years of 60.6%. Seventy-seven cases (34.1% of all cases) were diagnosed prenatally and these pregnancies were terminated. The prevalence of DS per 1000 births was significantly higher in older women, from 0.47 (95% CI 0.28-0.67) in mothers aged <30 years to 0.88 (95% CI 0.59-1.17) in mothers 30-<35 years (P<0.01), and to 4.74 (95% CI 3.95-5.53) in mothers ≥35 years (P<0.001). CONCLUSIONS: The prevalence of DS significantly increased with maternal age. About 35% of DS cases were detected prenatally and later terminated. Hence, examining only registry live births will result in an inaccurate prevalence rate of DS.

Subsequent gestational diabetes mellitus prediction in advanced maternal age using amniotic fluid glucose concentration during second trimester genetic amniocentesis.

This prospective study aimed to present the reference range of amniotic fluid glucose (AFglu) among second trimester pregnant women in southern Thailand, to evaluate the possibility of predicting subsequent gestational diabetes mellitus (GDM) using AFglu, and to estimate AFglu cut-off levels for identifying pregnancies at high or low risk for subsequent GDM in singleton pregnancies undergoing genetic amniocentesis due to advanced maternal age. A total of 438 eligible pregnant women were analysed, among whom 58 were subsequently diagnosed as having GDM. The reference range that included the central 95% of AFglu values at 16, 17 and 18 weeks of gestation in women not subsequently developing GDM was determined from a linear regression model. Logistic regression was used to identify predictors of subsequent GDM. Odds ratio of subsequent diagnosed GDM participant increased by 7% for each 1 mg/dl increase in AFglu. Risk of subsequent GDM was also increased in women aged over 36 years and in 17-18 weeks compared to 16 weeks of gestation. Depending on gestational and maternal age, AFglu levels above 51 to 75 mg/dl were at elevated risk of subsequent GDM (likelihood ratio 2.38). We conclude that AFglu tended to decrease with increasing of gestational age. Gestational age and maternal age accompanied with elevated AFglu are predictive factors for subsequent GDM.

Ductus venosus blood flow velocity waveforms during the early second trimester of pregnancy in a Thai population.

OBJECTIVE: To establish reference ranges for ductus venosus (DV) blood flow velocities and indices during the early second trimester. METHODS: A cross-sectional DV Doppler study of fetuses at 15-22 weeks of gestation was conducted at Songklanagarind Hospital, Songkhla, Thailand, during 2013-2014. The peak forward velocities were recorded and the DV indices were calculated. Predicted reference ranges based on the 5th and 95th percentiles according to the week of gestation were constructed. RESULTS: Among 371 fetuses, measurement of DV Doppler waveforms in the sagittal plane was achieved in 97.5% of cases. With advancing pregnancy (weeks 15 to 22), the DV velocities during ventricular systole, early diastole, and atrial contraction increased from 47.48 cm/s to 68.22 cm/s, 42.23 cm/s to 60.52 cm/s, and 15.94 cm/s to 34.84 cm/s, respectively. The time-averaged maximum value increased from 37.61 cm/s to 55.42 cm/s. The DV indices-pulsatility index for the vein, peak velocity index for the vein, preload index, and systolic/a-wave ratio-decreased from 0.79 to 0.59, 0.71 to 0.53, 0.63 to 0.47, and 2.72 to 1.90, respectively. The systolic/diastolic ratio remained relatively constant at 1.12. CONCLUSIONS: Normal reference ranges for DV flow velocities and indices during the early second trimester were established.

Accuracy of Ultrasonography Performed by Thai Maternal Fetal Medicine Fellowship at Songklanagarind Hospital for Fetal Sex Determination during Second Trimester Genetic Amniocentesis

Objective: To evaluate the accuracy of fetal sex determination using ultrasonography performed by Thai Maternal Fetal Medicine fellowships during second trimester genetic amniocentesis and also identify the possible factors of inaccurate determination. Material and Method: A prospective non-random study was conducted to evaluate the accuracy of fetal sex determination using ultrasonography performed by Thai Maternal Fetal Medicine fellows at Songklanagarind Hospital during second trimester genetic amniocentesis and also identify the possible factors of inaccurate determination. Results: Five hundred and sixty singleton pregnant women were enrolled. Eight cases were excluded due to abnormal fetal karyotype. No pregnancy loss or fetal ambiguous genitalia presented. The sex of 11/552 (1.99%) fetuses could not be adequately determined by ultrasonography. Overall, 491 of the 541 diagnose were correct ­ an accuracy of 90.8% (CI 88.0- 93.1) given an ultrasonographic diagnosis could be made. Among phenotypic females, the accuracy was 226/246, (91.9%; 95% CI 87.7-95.0) and among phenotypic males, the accuracy was 265/295 (89.8%; 95% CI 85.2-92.4). The ultrasonographic diagnosis of female sex was correct in 226/256, (88.3%; 95% CI 84.0-92.0), and the ultrasonographic diagnosis of male sex was correct in 265/285, (93.0%; 95% CI 89.4-95.7). For both sexes combined and for female fetuses, year of fellowship was only significant variable associated with correct sex determination by ultrasonography [2nd year vs. 1st year: overall ORS 2.55, (95% CI 1.44-4.61); female fetuses ORS 6.54, (95% CI 2.48-17.26)]. Conclusion: Fetal sex determination using ultrasonography by Thai Maternal Fetal Medicine Fellows at Songklanagarind Hospital during second trimester genetic amniocentesis is possible. Less experienced physicians should be had increased awareness especially in case of female external genitalia diagnosis.

Music Listening to Decrease Pain during Second Trimester Genetic Amniocentesis: A Randomized Trial.

Objective: To evaluate whether music listening decreased pain perception during second trimester genetic amniocentesis. Material and Method: We conducted a prospective randomized study to compare the pain perception using a visual analogue scale (VAS), pain rating, future decision to repeat the procedure, and pain perception compared to a venipuncture before and after the second trimester genetic amniocentesis between groups of pregnant women who underwent amniocentesis with and without music listening. Results: Three hundred thirty two pregnant women were enrolled; 161 listened and 171 did not listen to the music. The pre-procedure anxiety, the anticipated pain, post-procedure pain/ anxiety median VAS scores, pain rating, future decision and level of pain compare to a venipuncture in the music-listening and non-music-listening groups did not show statistically significant difference. The pre-procedure anxiety median VAS scores were 1.3 and 0.5 in the music-listening and non-musiclistening groups, respectively and the anticipated pain median VAS scores were 4.8 and 4.5 in the music-listening and non-music-listening groups, respectively. The post-procedure median VAS pain/anxiety scores were 2.7 and 2.5 in the music-listening and non-music-listening groups, respectively. Conclusion: Music listening was not significantly effective in reducing pain during second trimester genetic amniocentesis.

Reducing Pain and Anxiety during Second Trimester Genetic Amniocentesis Using Aromatic Therapy: A Randomized Trial.

OBJECTIVE: To evaluate the benefit of aromatic therapy using menthol for decrease pain perception during amniocentesis. MATERIAL AND METHOD: A prospective randomized study was conducted to compare pain level between groups ofpregnant women who underwent amniocentesis with and without aromatic therapy using menthol. Visual analogue scale (VAS) was usedfor pain assessment. The participants were askedfor their anticipated pain and anxiety level and level ofpain before and immediately after the procedure. RESULTS: Three hundred seventeen pregnant women were recruited into the present study, 158 in the menthol group and 159 in the non-menthol group. Mean VAS score of the post-procedure pain and anxiety did not differ significantly between the two groups. Mean VAS score of the anticipated pain influenced the mean VAS score of the pre-procedure anxiety and post-procedure pain and anxiety irrespective of the group. Mean VAS score of the pre-procedure anxiety and post-procedure pain and anxiety increased about 0.3 cm for each 1 cm of increasing mean VAS score of anticipated pain. CONCLUSION: Aromatic therapy using menthol was not significantly effective in reducing pain and anxiety during second trimester genetic amniocentesis.

A reference for ductus venosus blood flow at 11-13+6 weeks of gestation.

OBJECTIVE: To establish reference ranges for ductus venosus (DV) blood flow assessment obtained transabdominally at 11-13(+6) weeks of gestation. METHODS: A cross-sectional study was conducted on singleton pregnancies with a crown-rump length (CRL) ranging from 45 to 84 mm, normal fetus, and subsequent newborn birth weight appropriate for gestational age. Measurements of DV Doppler variables were performed by experienced sonographers: peak velocity during ventricular systole (S-wave) and diastole (D-wave), nadir during atrial contraction (A-wave), time-averaged maximum velocity (TAmax), pulsatility index for veins (PIV), and peak velocity index for veins (PVIV). RESULTS: A total of 304 fetuses were included. The mean CRL was 60.7 ± 7.2 mm (range: 45.9-75.5). The mean nuchal translucency measurement was 1.4 ± 0.4 mm. The S-wave, D-wave, A-wave, and TAmax values varied significantly with gestational age (p < 0.05) and regression models were constructed for each variable. The remaining variables, systolic/atrial wave ratio, preload index, PVIV, and PIV, did not vary significantly with gestational age within this CRL range. CONCLUSION: Reference ranges for DV Doppler assessment were established in normal fetuses. These ranges may be a useful tool for evaluation of anueploidy and fetal cardiac function.

Prevalence of neural tube defect in southern Thailand: a population-based survey during 2009-2012.

BACKGROUND: Neural tube defects (NTDs) are a group of congenital malformation of the central nervous system that leads to permanent physical disability and requires lifelong treatment. In Thailand, there have been three published articles on NTDs, all hospital-based studies, which found prevalence of NTDs of 4.8-6.7 per 10,000 live births. OBJECTIVE: It was our purpose with this study to determine the prevalence and type of NTDs in southern Thailand through a population-based survey. METHOD: Data were obtained through the population-based surveillance during 2009-2012 in three provinces (Songkhla, Phatthalung, Trang) in southern Thailand. Entries in the birth defects registry included all live births, all stillbirths after 24-week gestational age, and termination of pregnancy following the prenatal diagnosis at any gestational age of all congenital anomalies. RESULTS: During 2009-2012, 148,759 births were registered in the three provinces. Twenty-eight NTD cases were identified, giving an average of 1.88 per 10,000 births (95 % CI 1.20-2.51): 12 cases with anencephaly (42.8 %), 5 with occipital encephalocele (17.9 %), and 11 with myelomeningocele (39.3 %). The birth prevalence per 10,000 births of anencephaly, encephalocele, and myelomeningocele were 0.81, 0.33, and 0.74, respectively. Sixteen (57 %) were detected in live births, and 12 (43 %) were detected by prenatal diagnosis which later resulted in termination of pregnancy. CONCLUSIONS: The prevalence of NTDs based on the population-based study in southern Thailand was low. About 40 % of NTD cases were detected prenatally and later terminated. Hence, examining only registry live births will result in an inaccurately low NTD prevalence rate.