First trimester Down syndrome screening: public health implications

Factors associated with utilization of maternal serum screening for Down syndrome in mainland China: a cross-sectional study

BACKGROUND

Knowledge of the factors that influence maternal serum screening (MSS) service utilization can be used to develop health policies to promote equitable access to MSS and further diagnostic tests. The purpose of this study was to find the factors associated with utilization of MSS as well as the current status of service utilization in mainland China.

METHODS

This was a hospital-based cross-sectional study with respondents interviewed with a questionnaire designed based on Andersen's behavioral model. Descriptive statistics, univariate analysis, and multilevel logistic regression analysis were used to identify the factors associated with MSS utilization, and to explore potential methods to improve screening uptake.

RESULTS

A total of 8110 women who had given birth within the previous 7 days in one of 111 participating institutions from six provinces in mainland China were interviewed. Approximately 36% of the participants had used MSS. Women between 20 and 35 years, who resided in urban areas, were educated, were in a stable occupation, who had health knowledge, who attended maternal preparation classes, who had received eight or more prenatal checkups, who were from a region of higher social economic status, and who delivered in a tertiary healthcare institution were significantly more likely to use MSS than their counterparts. As compared with other factors, insufficient education is the single most important demographic factor for service underutilization.

CONCLUSIONS

Efforts should not only be made to target the population that underuses MSS, but the overall organization of MSS service delivery should be assessed during policy development to make access to MSS equitable to the entire population of mainland China.

'I want a choice, but I don't want to decide'--a qualitative study of pregnant women's experiences regarding early ultrasound risk assessment for chromosomal anomalies

OBJECTIVE

To increase our understanding of how pregnant women experience early ultrasound examination that includes a risk assessment for chromosomal anomalies and how such women perceive the test results.

DESIGN/SETTING

Qualitative study at St. Olavs Hospital in Norway. Both pre- and post-examination interviews were conducted with ten pregnant women who underwent risk assessment for chromosomal anomalies. Grounded theory was used to analyse the results.

FINDINGS

The study generated a core category (I want a choice, but I don't want to decide), which related to the conflict between choice and decision making. There were also five main categories (existential choices, search for knowledge, anxiety, feeling of guilt and counselling and care). The main categories describe the complex feelings experienced by the women regarding the risk assessment. Factors contributing to the difficulty of choice included loss of control and coping, emotional connection to the fetus and social pressure. As the women sought independent choices without any external influence, they also felt greater responsibility. The women's understanding of the actual risk varied, and they used different types of logic and methods to evaluate the risk and reach a decision.

CONCLUSIONS

The pregnant women in this study wanted prenatal diagnostic information and easy access to specialty services. Stress-related feelings and non-transparent information about the actual and perceived risks as well as personal moral judgments made the decision-making process complicated. Improved distribution of information and frequent contact with health professionals may help such women to make informed choices in accordance with their values and beliefs.

The triple test as a screening technique for Down syndrome: reliability and relevance

The triple test is a second trimester screening test used to identify those pregnant women who should be offered a diagnostic test to identify whether their fetus has an aneuploidy. It was first described in 1988, but has largely been superseded by newer tests either conducted earlier in the first trimester (ie, the combined test, using ultrasound measurement of nuchal translucency, pregnancy-associated plasma protein A, and human chorionic gonadotrophin [hCG]) or in the second trimester (ie, the quadruple test, using α-fetoprotein, hCG, uE3, and inhibin). These newer tests have been introduced because they offer greater detection and lower screen positive results thereby enhancing diagnosis rates, while decreasing the risk of iatrogenic harm caused by the invasive testing required when collecting suitable sample tissue. Noninvasive alternatives to the triple test have been identified, but these have not been adopted despite 13 years of development. It is likely, therefore, that the triple test (or variants thereof) will continue to be used in routine antenatal care for the foreseeable future.

Women's perceptions of access to prenatal care in the United States: a literature review

Women report many barriers to accessing prenatal care. This article reviews the literature from 1990 to the present on women's perceptions of access to prenatal care within the United States. Barriers can be classified into societal, maternal, and structural dimensions. Women may not be motivated to seek care, especially for unintended pregnancies. Societal and maternal reasons cited for poor motivation include a fear of medical procedures or disclosing the pregnancy to others, depression, and a belief that prenatal care is unnecessary. Structural barriers include long wait times, the location and hours of the clinic, language and attitude of the clinic staff and provider, the cost of services, and a lack of child-friendly facilities. Knowledge of women's views of access can help in development of policies to decrease barriers. Structural barriers could be reduced through changes in clinic policy and prenatal care format, and the creation of child-friendly waiting and examination rooms. Maternal and societal barriers can be addressed through community education. A focus in future research on facilitators of access can assist in creating open pathways to perinatal care for all women.

The impact of crown-rump length measurement error on combined Down syndrome screening: a simulation study

OBJECTIVE

To evaluate the impact of a 5-mm error in the measurement of crown-rump length (CRL) in a woman undergoing ultrasound and biochemistry sequential combined screening for Down syndrome.

METHODS

Based on existing risk calculation algorithms, we simulated the case of a 35-year-old-woman undergoing combined screening based on nuchal translucency (NT) measurement and early second-trimester maternal serum markers (human chorionic gonadotropin (hCG) and alpha-fetoprotein (AFP) expressed as multiples of the median (MoM)). Two measurement errors were considered (+ or - 5 mm), for four different CRLs (50, 60, 70 and 80 mm), with five different NT measurements (1, 1.5, 2, 2.5 and 3 mm) in a patient undergoing biochemistry testing at 14 + 4, 15, 16, 17 or 18 weeks' gestation. Four different values for each maternal serum marker were tested (1, 1.5, 2 and 2.5 MoM for hCG, and 0.5, 0.8, 1 and 1.5 MoM for AFP), leading to a total of 3200 simulations of the impact of measurement error. In all cases the ratio between the risk as assessed with or without the measurement error was calculated (measurement error-related risk ratio (MERR)).

RESULTS

Over 3200 simulated cases, MERR ranged from 0.53 to 2.14. In 586 simulations (18.3%), it was < 0.66 or > 1.33. Based on a risk cut-off of 1/300, women would have been misclassified in 112 simulations (3.5%). This would go up to 33 (27.5%) out of the 120 simulations in women with 'borderline' risk, with 1.5 MoM for hCG and 0.5 MoM for AFP, and NT measurement of 1 or 2mm.

CONCLUSION

Down syndrome screening may be highly sensitive to measurement errors in CRL. Quality control of CRL measurement should be performed together with quality control of NT measurement in order to provide the highest standard of care.

Antenatal care implications of population‐based trends in Down syndrome birth rates by rurality and antenatal care provider, Queensland, 1990–2004

OBJECTIVE

To assess whether the rates of Down syndrome births in Queensland vary according to rurality (ie, whether the mother lives in a rural or urban area) and type of antenatal care provider, and to consider any implications for antenatal care.

DESIGN AND SETTING

Population-based study of Down syndrome births in Queensland between 1990 and 2004, stratified by rurality and type of antenatal care provider (private obstetrician, public hospital or shared care).

RESULTS

Since 2000, there has been a large fall in maternal-age-adjusted rates of Down syndrome births among mothers living in urban areas (-14.3% per year; 95% CI, -22.7%, -5.0%) and among mothers receiving their antenatal care from private obstetricians (-27.5% per year; 95% CI, -37.6%, -15.8%). Similar decreases have not occurred among mothers living in rural areas (0.0%; 95% CI, -11.7%, 13.1%) or among mothers receiving antenatal care from public hospitals (+2.9%, 95% CI, -10.3%, 17.9%).

CONCLUSION

Possible reasons for the observed trends include unequal access to antenatal screening; confusion about screening guidelines and protocols; late presentation for antenatal care; and differences in attitudes to screening and termination of pregnancy among expectant parents, such that they may choose not to have screening or not to act on a positive screening test result.

A non-invasive test for prenatal diagnosis based on fetal DNA present in maternal blood: a preliminary study

BACKGROUND

Use of free fetal DNA to diagnose fetal chromosomal abnormalities has been hindered by the inability to distinguish fetal DNA from maternal DNA. Our aim was to establish whether single nucleotide polymorphisms (SNPs) can be used to distinguish fetal DNA from maternal DNA-and to determine the number of fetal chromosomes-in maternal blood samples.

METHODS

Formaldehyde-treated blood samples from 60 pregnant women and the stated biological fathers were analysed. Maternal plasma fractions were quantified at multiple SNPs, and the ratio of the unique fetal allele signal to the combined maternal and fetal allele signal calculated. The mean ratios of SNPs on chromosomes 13 and 21 were compared to test for potential fetal chromosomal abnormalities.

FINDINGS

The mean proportion of free fetal DNA was 34.0% (median 32.5%, range 17.0-93.8). We identified three samples with significant differences in the fetal DNA ratios for chromosome 13 and chromosome 21, indicative of trisomy 21; the remaining 57 samples were deemed to be normal. Amniocentesis or newborn reports from the clinical sites confirmed that the copy number of fetal chromosomes 13 and 21 was established correctly for 58 of the 60 samples, identifying 56 of the 57 normal samples, and two of the three trisomy 21 samples. Of the incorrectly identified samples, one was a false negative and one was a false positive. The sensitivity and positive predictive value were both 66.7% (95% CI 12.5-98.2) and the specificity and negative predictive values were both 98.2% (89.4-99.9).

INTERPRETATION

The copy number of chromosomes of interest can be directly established from maternal plasma. Such a non-invasive prenatal test could provide a useful complement to currently used screening tests.

Education and quality review for nuchal translucency ultrasound

First trimester nuchal translucency ultrasound has evolved from an ultrasound measurement used only in a research setting to a screening tool which is being offered to the general obstetric population. Studies of nuchal translucency suggest great variation in Down syndrome detection rates which may be secondary to significant differences in sonographic training and nuchal translucency image quality. Inaccurate screening has the potential to adversely impact patients. This paper will explore: (1) why quality review in nuchal translucency ultrasound is important, (2) methods of nuchal translucency quality assessment, (3) experience with quality review in the research setting, and (4) current strategies for quality assessment in patient care.