Chanane Wanapirak

Noninvasive prenatal diagnosis of monogenic diseases by digital size selection and relative mutation dosage on DNA in maternal plasma

Prenatal diagnosis of monogenic diseases, such as cystic fibrosis and β-thalassemia, is currently offered as part of public health programs. However, current methods based on chorionic villus sampling and amniocentesis for obtaining fetal genetic material pose a risk to the fetus. Since the discovery of cell-free fetal DNA in maternal plasma, the noninvasive prenatal assessment of paternally inherited traits or mutations has been achieved. Due to the presence of background maternal DNA, which interferes with the analysis of fetal DNA in maternal plasma, noninvasive prenatal diagnosis of maternally inherited mutations has not been possible. Here we describe a digital relative mutation dosage (RMD) approach that determines if the dosages of the mutant and wild-type alleles of a disease-causing gene are balanced or unbalanced in maternal plasma. When applied to the testing of women heterozygous for the CD41/42 (–CTTT) and hemoglobin E mutations on HBB, digital RMD allows the fetal genotype to be deduced. The diagnostic performance of digital RMD is dependent on interplay between the fractional fetal DNA concentration and number of DNA molecules in maternal plasma. To achieve fetal genotype diagnosis at lower volumes of maternal plasma, fetal DNA enrichment is desired. We thus developed a digital nucleic acid size selection (NASS) strategy that effectively enriches the fetal DNA without additional plasma sampling or experimental time. We show that digital NASS can work in concert with digital RMD to increase the proportion of cases with classifiable fetal genotypes and to bring noninvasive prenatal diagnosis of monogenic diseases closer to reality.

Single transvaginal sonographic measurement of cervical length early in the third trimester as a predictor of preterm delivery

Objective To evaluate the accuracy of a single sonographic measurement of cervical length early in the third trimester as a predictor of preterm delivery. Methods A total of 771 women attending the antenatal clinic at the Maharaj Nakorn Chiang Mai Hospital between January 1, 1990, and November 30, 1993, with singleton gestations, cervical competence, accurate dates of last menstrual period, and gestational ages between 28–30 weeks, were recruited into the study. Forty-one were excluded, ten because of induced preterm delivery, 24 because of measurement problems, and seven because they were lost to follow-up. We analyzed the remaining 730 women. Results Ninety-one (12.5%) women ended with preterm births and the remaining 639 (87.5%) delivered at term. The mean (± standard deviation) cervical lengths of the term and preterm groups were statistically significantly different at 37 ± 5 and 34 ± 6 mm, respectively (P < .001). The likelihood ratio of cervical length at various cutoff points was calculated. The appropriate cutoff point based on the receiver operating characteristic curve (35 mm) was associated with a significantly increased likelihood of preterm delivery (20 versus 7%) and was detected in two-thirds of preterm births. This cutoff point gave a sensitivity and specificity of 65.9 ± 5.1% (95% confidence interval [CI]) and 62.4 ± 5.2% (95% CI), respectively. Conclusion A single transvaginal sonographic measurement of cervical length at 28–30 gestational weeks can be used to predict the risk of preterm delivery, using a cutoff point of 35 mm, but its cost-effectiveness should be assessed further.

Risk factors for HIV-1 transmission from HIV-seropositive male blood donors to their regular female partners in northern Thailand.

Objective:To describe risks for HIV transmission from male blood donors to their regular female sex partners in Chiang Mai, Thailand. Design:Cross-sectional study. Methods:From March 1992 through September 1995, 405 HIV-seropositive male blood donors (index cases) and their regular female partners were enrolled in the study. Women with risk factors for HIV infection other than sexual contact with the index male were excluded. Couples were interviewed and examined; specimens were collected for laboratory analysis. Results:Overall, 46% of the 405 women enrolled were HIV-positive. Ninety-eight per cent of male index cases had a history of sex with a female prostitute; 1.5% reported always using condoms with their regular partner. History of sexually transmitted disease (STD) and swollen inguinal lymph nodes in the female partner were associated with an increased risk of HIV infection in the female. History in the female of genital herpes [odds ratio (OR), 3.46; 95% confidence interval (CI), 1.50–8.78], gonorrhea or chlamydia infection (OR, 2.71; 95% CI, 1.39–5.53), and stable relationship of longer than 24 months (OR, 2.28; 95% CI, 1.02–5.09) were associated with an increased risk of HIV infection in the female. Consistent condom use in the past 2 years (OR, 0.10; 95% CI, 0.01–0.79) was associated with a decreased risk of HIV infection in the female. Conclusions:Married women in northern Thailand who appear otherwise to be at low risk for HIV infection may be exposed to this virus by their husbands. High rates of sex with commercial sex workers among men and low use of condoms within stable relationships may be important factors promoting the transmission of HIV in married couples. Programs to increase the regular use of condoms among married couples could be an important public health intervention to prevent transmission of HIV and other types of STD in northern Thailand.

Sonographic Markers of Hemoglobin Bart Disease at Midpregnancy

Objective. To evaluate the efficacy of various sonographic markers at midpregnancy in predicting fetal hemoglobin Bart disease. Methods. Four hundred eighty‐eight pregnancies at risk of having fetuses with hemoglobin Bart disease were recruited for prenatal diagnosis with cordocentesis at 18 to 21 gestational weeks. Before cordocentesis, the sonographic markers, including cardiothoracic ratio, placental thickness, pericardial effusion, pleural effusion, ascites, subcutaneous edema, cord edema, dilated umbilical vein, and amniotic fluid index, were assessed and recorded. The definite fetal diagnosis was based on blood analysis. The efficacy of each sonographic marker in predicting hemoglobin Bart disease was evaluated by sensitivity and specificity. Results. Among 488 pregnancies undergoing prenatal diagnosis, 100 fetuses were proved to be affected by hemoglobin Bart disease. The cardiothoracic ratio gave the highest sensitivity, 95.0%, with specificity of 96.1%, followed by placental thickness. Signs of hydrops fetalis were observed in 33.0% of cases; they did not increase the sensitivity of the cardiothoracic ratio but strongly reinforced the diagnosis when they appeared. Conclusions. At midpregnancy, sonographic markers can effectively differentiate normal pregnancies from those with fetal hemoglobin Bart disease. Among couples at risk with no sonographic markers, the risk of having an affected child is nearly eliminated. The most sensitive marker was the cardiothoracic ratio, followed by placental thickness.

Cordocentesis at 16-24 weeks of gestation: experience of 1320 cases

The objective of this study was to assess the safety and efficacy of diagnostic cordocentesis at midpregnancy. 1320 singleton pregnancies with no obvious congenital anomalies, a gestational age of 16–24 weeks, and proper indications underwent cordocentesis using the freehand technique. The results of each procedure was prospectively collected and subsequently analysed for the results and pregnancy outcomes. The mean maternal age was 31.1 years and the mean gestational age at the time of cordocentesis was 19.8 weeks. The most common indication was the risk of severe thalassaemia syndrome (69.8%) and was followed by rapid karyotyping. Of 1320 cordocenteses, 1281 (97%) were done successfully at the first attempt. The mean duration of the procedure was 10.5 min and was significantly longer in the first 50 cases of practice for each operator. The maternal blood contamination rate was higher when the cord insertion was targeted. The procedure‐related complications included transient bleeding at puncture site (20.2%), transient fetal bradycardia (4.3%), chorioamnionitis (two cases), and cord haematoma (one case). Of 1281 successful cases, 184 fetuses had severe disease. The total fetal loss rate was 3.2% and the procedure‐related loss was 1%. The other obstetric complications were comparable with those in the general population. We conclude that cordocentesis at midpregnancy is a useful, relatively safe, and effective procedure for prenatal diagnosis. Copyright

Alcoholization: The choice of intrauterine treatment for chorioangioma

Chorioangioma is a vascular tumor of the placenta. Most are small and asymptomatic, whereas the large tumors are clinically significant and often associated with polyhydramnios and fetal heart failure. To prevent fetal loss from these complications, many interventions have been proposed, including intrauterine transfusion in anemic cases and fetoscopic surgery to ablate the feeding vessels. The case presented herein had large chorioangiomas, 8 and 4 cm in diameter, associated with polyhydramnios and early signs of hydrops fetalis, diagnosed at 27 weeks gestation. After extensive counseling, we performed alcohol ablation of the feeding vessel of the larger tumor. Signs of fetal heart failure and hydrops fetalis disappeared dramatically. The pregnancy was extended for 2 weeks, followed by premature rupture of the membranes and spontaneous labor at 32 weeks gestation and a surviving female baby, weighing 1360 g, was delivered uneventfully. This preliminary experience suggests that alcoholization may be one of the best choices for this condition due to its high efficacy, simplicity, safety and very low cost. To our knowledge, this is the first report using alcoholization for the treatment of hydrops fetalis secondary to chorioangioma.

Antenatal sonographic features of 100 alpha-thalassemia hydrops fetalis fetuses.

To characterize the sonographic findings of α‐thalassemia hydrops fetalis.

Transvaginal ultrasound in threatened abortions with empty gestational sacs

Objective: To determine whether transvaginal ultrasound criteria alone can distinguish viable from non‐viable gestational sacs at a single examination. Method: A prospective descriptive study was undertaken and analysis performed on 211 pregnancies complicated by threatened abortion and empty gestation sacs diagnosed by transvaginal ultrasound. The main outcome measure was the final diagnosis of viable or non‐viable gestation on subsequent transvaginal sonography. Results: The study shows that a single transvaginal ultrasound examination is useful in differentiating viable from non‐viable gestation sacs. The mean sac diameter (MSD) was found to be the most useful criterion for determining non‐viability. An MSD of ≥ 17 mm that lacked an embryo and an MSD of ≥ 13 mm without visible yolk sac were reliable predictors of non‐viable gestation sacs at a single examination with 100% specificity and 100% positive predictive value. An MSD ≥ 13 mm without visible yolk sac was the most sensitive criterion. Using MSD criteria, 73% of non‐viable gestations could be reliably identified without any false‐positive diagnoses. Deformed shape, low position and thin decidual reaction are strong indicators of non‐viable gestations but are not 100% accurate. There is still a significant proportion of empty sacs, where no accurate distinction between viable and non‐viable can be made according to one criterion at a single examination and in these cases serial examinations should be carried out before any active management is advocated. Conclusion: In most cases, transvaginal sonographic criteria alone can distinguish viable from non‐viable empty gestational sacs at a single examination.

Prenatal sonographic diagnosis of VATER association.

We examined the potential role of sonography in the prenatal diagnosis of the VATER association, a spectrum of fetal anomalies that includes vertebral defects, imperforate anus, tracheoesophageal fistula, and radial and renal dysplasia.

Sonographic features of trisomy 18 at midpregnancy

Objective:  To evaluate the sonographic characteristics of the fetuses with trisomy 18 at 16–22 weeks of gestation.