INTRODUCTIONFirst trimester screening (FTS) is a validated screening tool that has been shown to achieve detection rates of 84%-90% for trisomies 21, 18 and 13. However, its effectiveness for different maternal ages has not been assessed. The present study aimed to assess the performance of FTS in an Asian population, and to compare its effectiveness in older (≥ 35 years) and younger (< 35 years) women. The potential use of noninvasive prenatal test (NIPT) as a contingent screening test is also examined.

METHODSData on cases of FTS performed on singleton pregnancies over a six-year period was collated from two Singapore maternal centres, National University Hospital and Singapore General Hospital. Cases that had a 1:250 risk of trisomy were considered to be screen-positive. Pregnancy outcomes were obtained from birth records or karyotype test results.

RESULTSFrom 10,289 FTS cases, we obtained a sensitivity of 87.8%, a specificity of 97.6%, a false positive rate of 2.4% and a false negative rate of 0.06% for the detection of aneuploidy. The overall detection rate for trisomy 21 was 86.5%-85.7% for older women and 87.5% for younger women. The mean number of invasive tests required per case of trisomy 21 was 9.3 in younger women, 8.6 in older women and 13.5 in women with intermediate risk (1:250-1,000).

CONCLUSIONWhile the performance of FTS was similar in younger and older women, more invasive procedures were required to diagnose trisomy 21 in women with intermediate risk. It may be advantageous to offer contingent NIPT to this group of women to reduce the risk of iatrogenic fetal loss.

Adolescent ; Adult ; Aneuploidy ; Asia ; Cohort Studies ; DNA ; analysis ; Down Syndrome ; diagnosis ; Female ; Humans ; Karyotyping ; Maternal Age ; Maternal Serum Screening Tests ; methods ; Middle Aged ; Pregnancy ; Pregnancy Outcome ; Pregnancy Trimester, First ; Prenatal Diagnosis ; methods ; Risk Factors ; Singapore ; Trisomy ; diagnosis

Female ; Humans ; Maternal Age ; Maternal Serum Screening Tests ; methods ; Pregnancy ; Pregnancy Trimester, First ; Prenatal Diagnosis ; methods

INTRODUCTIONInvasive prenatal diagnosis (IPD) has long been used to prenatally diagnose Down syndrome (DS), but it is associated with a small risk of miscarriage. Noninvasive prenatal testing (NIPT) is a highly sensitive screening test using cell-free DNA in maternal blood for detection of DS without the risk of miscarriage, but it confers a small risk of false-positive and false-negative results. The implementation of these procedures into clinical practice requires an understanding of stakeholder preferences.

METHODSA total of 69 health professionals (HPs) and 301 women took part in a discrete choice experiment (DCE) in which preferences for four prenatal test attributes - accuracy, time of results, risk of miscarriage and amount of information provided - were assessed. Conditional logit regression was used to analyse the data. Data on demographics and ranked preferences for test attributes was collected, and a direct choice question regarding NIPT, IPD or neither test was posed to participants.

RESULTSThe women showed a preference for test safety, whereas HPs prioritised test accuracy above all other attributes. When offered a direct choice of NIPT, IPD or neither test, women aged 35 years and older, those with previous miscarriage or who knew a child with DS were more likely to choose NIPT. Chinese women preferred NIPT, whereas Indian women preferred IPD.

CONCLUSIONOur data highlights the need for patient-specific counselling, taking into account previous experiences and cultural factors. Since women and HPs prioritise different test attributes, it is essential that HPs recognise these differences in order to provide non-biased counselling.