The art of vaginal breech birth at term on all fours.

Despite a shift in clinical practice favouring cesarean section for breech presentation, adequate skills are still needed for a safe vaginal breech birth. This case report illustrates the physiological mechanism of vaginal breech birth. The accompanying pictures are a testimony to the "hands-off" approach and could be used for educational purposes.

Economic analysis comparing induction of labor and expectant management in women with preterm prelabor rupture of membranes between 34 and 37 weeks (PPROMEXIL trial).

OBJECTIVE: To compare the costs of induction of labor and expectant management in women with preterm prelabor rupture of membranes (PPROM). DESIGN: Economic analysis based on a randomized clinical trial. SETTING: Obstetric departments of eight academic and 52 non-academic hospitals in the Netherlands. POPULATION: Women with PPROM near term who were not in labor 24 h after PPROM. METHODS: A cost-minimization analysis was done from a health care provider perspective, using a bottom-up approach to estimate resource utilization, valued with unit-costs reflecting actual costs. MAIN OUTCOME MEASURES: Primary health outcome was the incidence of neonatal sepsis. Direct medical costs were estimated from start of randomization to hospital discharge of mother and child. RESULTS: Induction of labor did not significantly reduce the probability of neonatal sepsis [2.6% vs. 4.1%, relative risk 0.64 (95% confidence interval 0.25-1.6)]. Mean costs per woman were €8094 for induction and €7340 for expectant management (difference €754; 95% confidence interval -335 to 1802). This difference predominantly originated in the postpartum period, where the mean costs were €5669 for induction vs. €4801 for expectant management. Delivery costs were higher in women allocated to induction than in women allocated to expectant management (€1777 vs. €1153 per woman). Antepartum costs in the expectant management group were higher because of longer antepartum maternal stays in hospital. CONCLUSIONS: In women with pregnancies complicated by PPROM near term, induction of labor does not reduce neonatal sepsis, whereas costs associated with this strategy are probably higher.

Induction of labor versus expectant management in women with preterm prelabor rupture of membranes between 34 and 37 weeks: a randomized controlled trial.

BACKGROUND: At present, there is insufficient evidence to guide appropriate management of women with preterm prelabor rupture of membranes (PPROM) near term. METHODS AND FINDINGS: We conducted an open-label randomized controlled trial in 60 hospitals in The Netherlands, which included non-laboring women with >24 h of PPROM between 34(+0) and 37(+0) wk of gestation. Participants were randomly allocated in a 1:1 ratio to induction of labor (IoL) or expectant management (EM) using block randomization. The main outcome was neonatal sepsis. Secondary outcomes included mode of delivery, respiratory distress syndrome (RDS), and chorioamnionitis. Patients and caregivers were not blinded to randomization status. We updated a prior meta-analysis on the effect of both interventions on neonatal sepsis, RDS, and cesarean section rate. From 1 January 2007 to 9 September 2009, 776 patients in 60 hospitals were eligible for the study, of which 536 patients were randomized. Four patients were excluded after randomization. We allocated 266 women (268 neonates) to IoL and 266 women (270 neonates) to EM. Neonatal sepsis occurred in seven (2.6%) newborns of women in the IoL group and in 11 (4.1%) neonates in the EM group (relative risk [RR] 0.64; 95% confidence interval [CI] 0.25 to 1.6). RDS was seen in 21 (7.8%, IoL) versus 17 neonates (6.3%, EM) (RR 1.3; 95% CI 0.67 to 2.3), and a cesarean section was performed in 36 (13%, IoL) versus 37 (14%, EM) women (RR 0.98; 95% CI 0.64 to 1.50). The risk for chorioamnionitis was reduced in the IoL group. No serious adverse events were reported. Updating an existing meta-analysis with our trial results (the only eligible trial for the update) indicated RRs of 1.06 (95% CI 0.64 to 1.76) for neonatal sepsis (eight trials, 1,230 neonates) and 1.27 (95% CI 0.98 to 1.65) for cesarean section (eight trials, 1,222 women) for IoL compared with EM. CONCLUSIONS: In women whose pregnancy is complicated by late PPROM, neither our trial nor the updated meta-analysis indicates that IoL substantially improves pregnancy outcomes compared with EM. TRIAL REGISTRATION: Current Controlled Trials ISRCTN29313500

Ethnic differences in participation in prenatal screening for Down syndrome: a register-based study.

OBJECTIVE: To assess ethnic differences in participation in prenatal screening for Down syndrome in the Netherlands. METHODS: Participation in prenatal screening was assessed for the period 1 January 2009 to 1 July 2009 in a defined postal code area in the southwest of the Netherlands. Data on ethnic origin, socio-economic background and age of participants in prenatal screening were obtained from the Medical Diagnostic Centre and the Department of Clinical Genetics. Population data were obtained from Statistics Netherlands. Logistic regression models were used to assess ethnic differences in participation, adjusted for socio-economic and age differences. RESULTS: The overall participation in prenatal screening was 3865 out of 15 093 (26%). Participation was 28% among Dutch women, 15% among those from Turkish ethnic origin, 8% among those from North-African origin, 15% among those from Aruban/Antillean origin and 26% among women from Surinamese origin. CONCLUSIONS: Compared to Dutch women, those from Turkish, North-African, Aruban/Antillean and other non-Western ethnic origin were less likely to participate in screening. It was unexpected that women from Surinamese origin equally participated. It should be further investigated to what extent participation and non-participation in these various ethnic groups was based on informed decision-making.

Ethnic and socio-economic differences in uptake of prenatal diagnostic tests for Down's syndrome.

OBJECTIVE: The objective of this study was to assess ethnic and socio-economic differences in the uptake of maternal age-based prenatal diagnostic testing for Down's syndrome by amniocentesis or chorionic villus sampling. STUDY DESIGN: The study population consisted of 12,340 women aged 36 years or over, who lived in a geographically defined region in the Southwest of The Netherlands and who gave birth to a live born infant in the period 2000-2004. Data were obtained from the Department of Clinical Genetics Erasmus MC and Statistics Netherlands. Logistic regression analyses were done to assess ethnic and socio-economic differences in uptake. RESULTS: The overall uptake of prenatal diagnostic tests was 28.5%. Women of Turkish and Caribbean origin participated in prenatal diagnostic tests equally or more often than Dutch women. Women of North-African origin and women from low socio-economic background had a lower uptake than others. Ethnic differences in uptake could not be attributed to differences in socio-economic background. CONCLUSIONS: Uptake of prenatal diagnostic tests for Down's syndrome in The Netherlands was low and varied among ethnic and socio-economic groups of advanced maternal age. The finding that women of Turkish and Caribbean origin participated in prenatal diagnostic tests equally or more often than Dutch women was unexpected. The low uptake among Dutch women may be related to the Dutch pregnancy culture. The finding that women of North-African origin and women from low socio-economic background had a lower uptake may be related to barriers in access to prenatal diagnostic tests.

The association of daily physical activity and birth outcome: a population-based cohort study.

The potential relationship between daily physical activity and pregnancy outcome remains unclear because of the wide variation in study designs and physical activity assessment measures. We sought to prospectively quantify the potential effects of the various domains of physical activity on selected birth outcomes in a large unselected population. The sample consisted of 11,759 singleton pregnancies from the Avon longitudinal study of parents and children, United Kingdom. Information on daily physical activity was collected by postal questionnaire for self-report measures. Main outcome measures were birth weight, gestational age at delivery, preterm birth and survival. After controlling for confounders, a sedentary lifestyle and paid work during the second trimester of pregnancy were found to be associated with a lower birth weight, while 'bending and stooping' and 'working night shifts' were associated with a higher birth weight. There was no association between physical exertion and duration of gestation or survival. Repetitive boring tasks during the first trimester was weakly associated with an increased risk of preterm birth (<37 weeks) (adjusted odds ratio [OR] = 1.25, 95% CI 1.04-1.50). 'Bending and stooping' during the third trimester was associated with a reduced risk of preterm birth (adjusted OR = 0.73, 95% CI 0.63-0.84). Demanding physical activities do not have a harmful effect on the selected birth outcomes while a sedentary lifestyle is associated with a lower birth weight. In the absence of either medical or obstetric complications, pregnant women may safely continue their normal daily physical activities should they wish to do so.

Estimating the effect of gestational age on test performance of combined first-trimester screening for Down syndrome: a preliminary study.

OBJECTIVE: To establish how different methods of estimating gestational age (GA) affect reliability of first-trimester screening for Down syndrome. METHODS: Retrospective single-center study of 100 women with a viable singleton pregnancy, who had first-trimester screening. We calculated multiples of the median (MoM) for maternal-serum free beta human chorionic gonadotropin (free beta-hCG) and pregnancy associated plasma protein-A (PAPP-A), derived from either last menstrual period (LMP) or ultrasound-dating scans. RESULTS: In women with a regular cycle, LMP-derived estimates of GA were two days longer (range -11 to 18), than crown-rump length (CRL)-derived estimates of GA whereas this discrepancy was more pronounced in women who reported to have an irregular cycle, i.e., six days (range -7 to 32). Except for PAPP-A in the regular-cycle group, all differences were significant. Consequently, risk estimates are affected by the mode of estimating GA. In fact, LMP-based estimates revealed ten "screen-positive" cases compared to five "screen-positive" cases where GA was derived from dating-scans. CONCLUSION: Provided fixed values for nuchal translucency are applied, dating-scans reduce the number of screen-positive findings on the basis of biochemical screening. We recommend implementation of guidelines for Down syndrome screening based on CRL-dependent rather than LMP-dependent parameters of GA.

Ethnic differences in informed decision-making about prenatal screening for Down's syndrome.

BACKGROUND: The aim of this study was to assess ethnic variations in informed decision-making about prenatal screening for Down's syndrome and to examine the contribution of background and decision-making variables. METHODS: Pregnant women of Dutch, Turkish and Surinamese origin were recruited between 2006 and 2008 from community midwifery or obstetrical practices in The Netherlands. Each woman was personally interviewed 3 weeks (mean) after booking for prenatal care. Knowledge, attitude and participation in prenatal screening were assessed following the 'Multidimensional Measure of Informed Choice' that has been developed and applied in the UK. RESULTS: In total, 71% of the Dutch women were classified as informed decision-makers, compared with 5% of the Turkish and 26% of the Surinamese women. Differences between Surinamese and Dutch women could largely be attributed to differences in educational level and age. Differences between Dutch and Turkish women could mainly be attributed to differences in language skills and gender emancipation. CONCLUSION: Women from ethnic minority groups less often made an informed decision whether or not to participate in prenatal screening. Interventions to decrease these ethnic differences should first of all be aimed at overcoming language barriers and increasing comprehension among women with a low education level. To further develop diversity-sensitive strategies for counselling, it should be investigated how women from different ethnic backgrounds value informed decision-making in prenatal screening, what decision-relevant knowledge they need and what they take into account when considering participation in prenatal screening.

Ethnic differences in considerations whether or not to participate in prenatal screening for Down syndrome.

OBJECTIVE: To evaluate ethnic differences in considerations whether or not to participate in prenatal screening for Down syndrome and to relate these to differences in participation. METHOD: The study population consisted of 270 pregnant women from Dutch, Turkish and Surinamese (African and South Asian) ethnic origin, attending midwifery or obstetrical practices in the Netherlands. Women were interviewed after booking for prenatal care. Considerations were assessed by one open-ended question and 18 statements that were derived from focus group interviews. Actual participation was assessed several months later. RESULTS: Women from ethnic minorities were less likely to participate in prenatal screening, which could be attributed to differences in age and religious identity. They more often reported acceptance of 'what God gives', low risk of having a child with Down syndrome and costs of screening as considerations not to participate in prenatal screening. They also reported many considerations in favour of participation, which did not differ from those of Dutch women but were less often consistent with actual participation in screening. CONCLUSIONS: Women from ethnic minorities should not be stereotyped as being uninterested in prenatal screening, but should be better informed about the consequences of prenatal screening and Down syndrome.

[Prenatally detected orofacial cleft]. / Prenataal vastgestelde orofaciale schisis.

An increasing number of pregnancies are presumed being terminated following prenatal detection of orofacial cleft during structural ultrasound.After examining the data and literature on this topic it is concluded that the reported cases are merely incidents. For the interpretation of prenatal detection rates a distinction should be made between isolated orofacial cleft and the frequently occurring associated form of orofacial cleft which is usually characterized by other, often major structural or chromosome anomalies. The ultrasound detection rate of the isolated form is low and varies in the literature between 18 and 56%. Together with all Dutch centres of prenatal medicine a care plan was adopted for the management of prenatally detected orofacial cleft including diagnosis (detailed ultrasound examination and karyotyping), medical support (genetic consultations, plastic surgery and psychosocial counselling) and treatment (obstetric and neonatal management). In the presence of associated major congenital anomalies termination of pregnancy may be considered before the 24th week of pregnancy.

Rapid aneuploidy detection with multiplex ligation-dependent probe amplification: a prospective study of 4000 amniotic fluid samples.

The introduction of prenatal screening requires rapid high-throughput diagnosis of common aneuploidies. Multiplex ligation-dependent probe amplification (MLPA) allows for quick, easily automated multiplex testing of these aneuploidies in one polymerase chain reaction. We performed a large prospective study using MLPA on 4000 amniotic fluid (AF) samples including all indications and compared its value to karyotyping and fluorescence in situ hybridization (FISH). MLPA can reliably determine common aneuploidies with 100% sensitivity and 100% specificity. Moreover, some mosaic cases and structural chromosome aberrations were detected as well. In cases of a male fetus, triploidies can be detected by an aberrant pattern of probe signals, which mimics maternal cell contamination (MCC). Macroscopic blood contamination was encountered in 3.2% of the AF samples. In 20% of these samples, an MLPA pattern was found consistent with MCC, although there were no false negatives of the most common aneuploidies. As the vast majority of inconclusive results (1.7%) is due to potential MCC, we designed a protocol in which we determine whether MLPA can be performed on blood-contaminated AF samples by testing if blood is of fetal origin. Then, the number of inconclusive results could be theoretically reduced to 0.05%. We propose an alternative interpretation of relative probe signals for rapid aneuploidy diagnosis (RAD). We discuss the value of MLPA for the detection of (submicroscopic) structural chromosome anomalies. MLPA is a reliable method that can replace FISH and could be used as a stand-alone test for RAD instead of karyotyping.

Decision-making after ultrasound diagnosis of fetal abnormality.

During the last few decades, the use of ultrasonography for the detection of fetal abnormalities has become widespread in many industrialised countries. This resulted in a shift in timing of the diagnosis of congenital abnormalities in infants from the neonatal period to the prenatal period. This has major implications for both clinicians and the couples involved. In case of ultrasound diagnosis of fetal anomaly there are several options for the obstetric management, ranging from standard care to non-aggressive care to termination of pregnancy. This essay explores the context of both clinical and parental decision-making after ultrasound diagnosis of fetal abnormality, with emphasis on the Dutch situation. While normal findings at ultrasound examination have strong beneficial psychological effects on the pregnant woman and her partner, the couple are often ill-prepared for bad news about the health of their unborn child in the case of abnormal findings. When parents consider end-of-life decisions, they experience both ambivalent and emotional feelings. On the one hand, they are committed to their pregnancy; on the other hand, they want to protect their child, themselves and the family from the burden of severe disability. These complex parental reactions have implications for the counselling strategy.

Jugular lymphatic sacs in the first trimester of pregnancy: the prevalence and the potential value in screening for chromosomal abnormalities.

OBJECTIVE: To investigate the prevalence of detectable jugular lymphatic sacs in a setting for first trimester screening for Down syndrome, and to evaluate the influence of jugular lymphatic sacs on the screening performance for chromosomal abnormalities. METHODS: A prospective single center study (Erasmus University Medical Center, Rotterdam, The Netherlands) over a period of one year (January 2003-February 2004). First trimester nuchal translucency measurement was performed in a study population of 415 fetuses. Additionally, the transversal plane with the spine and mandible was visualized to verify the presence of jugular lymphatic sacs. The jugular lymphatic sacs were measured anterior-posterior. The association between nuchal translucency and jugular lymphatic sacs was tested. RESULTS: Follow-up was complete in 406 cases (97.8%). Jugular lymphatic sacs could be visualized in 98 out of 415 (23.5%). The nuchal translucency thickness and the mean of the left and right jugular lymphatic sac were significantly correlated. CONCLUSION: The sonographic visualization of jugular lymphatic sacs significantly predicts chromosomal abnormalities, although nuchal translucency is a better predictor. Nuchal translucency and jugular lymphatic sacs are strongly correlated and therefore not applicable in a combination test.

Multiplex ligation-dependent probe amplification versus karyotyping in prenatal diagnosis: the M.A.K.E. study.

BACKGROUND: In the past 30 years karyotyping was the gold standard for prenatal diagnosis of chromosomal aberrations in the fetus. Traditional karyotyping (TKT) has a high accuracy and reliability. However, it is labor intensive, the results take 14-21 days, the costs are high and unwanted findings such as abnormalities with unknown clinical relevance are not uncommon. These disadvantages challenged the practice of karyotyping. Multiplex ligation-dependent probe amplification (MLPA) is a new molecular genetic technique in prenatal diagnosis. Previous preclinical evidence suggests equivalence of MLPA and traditional karyotyping (TKT) regarding test performance. METHODS/DESIGN: The proposed study is a multicentre diagnostic substitute study among pregnant women, who choose to have amniocentesis for the indication advanced maternal age and/or increased risk following prenatal screening test. In all subjects, both MLPA and karyotyping will be performed on the amniotic fluid sample. The primary outcome is diagnostic accuracy. Secondary outcomes will be maternal quality of life, women's preferences and costs. Analysis will be intention to treat and per protocol analysis. Quality of life analysis will be carried out within the study population. The study aims to include 4500 women. DISCUSSION: The study results are expected to help decide whether MLPA can replace traditional karyotyping for 'low-risk' pregnancies in terms of diagnostic accuracy, quality of life and women's preferences. This will be the first clinical study to report on all relevant aspects of the potential replacement. TRIAL REGISTRATION: The protocol is registered in the clinical trial register number ISRCTN47252164.

Induction of labour versus expectant management in women with preterm prelabour rupture of membranes between 34 and 37 weeks (the PPROMEXIL-trial).

BACKGROUND: Preterm prelabour rupture of the membranes (PPROM) is an important clinical problem and a dilemma for the gynaecologist. On the one hand, awaiting spontaneous labour increases the probability of infectious disease for both mother and child, whereas on the other hand induction of labour leads to preterm birth with an increase in neonatal morbidity (e.g., respiratory distress syndrome (RDS)) and a possible rise in the number of instrumental deliveries. METHODS/DESIGN: We aim to determine the effectiveness and cost-effectiveness of immediate delivery after PPROM in near term gestation compared to expectant management. Pregnant women with preterm prelabour rupture of the membranes at a gestational age from 34+0 weeks until 37+0 weeks will be included in a multicentre prospective randomised controlled trial. We will compare early delivery with expectant monitoring. The primary outcome of this study is neonatal sepsis. Secondary outcome measures are maternal morbidity (chorioamnionitis, puerperal sepsis) and neonatal disease, instrumental delivery rate, maternal quality of life, maternal preferences and costs. We anticipate that a reduction of neonatal infection from 7.5% to 2.5% after induction will outweigh an increase in RDS and additional costs due to admission of the child due to prematurity. Under these assumptions, we aim to randomly allocate 520 women to two groups of 260 women each. Analysis will be by intention to treat. Additionally a cost-effectiveness analysis will be performed to evaluate if the cost related to early delivery will outweigh those of expectant management. Long term outcomes will be evaluated using modelling. DISCUSSION: This trial will provide evidence as to whether induction of labour after preterm prelabour rupture of membranes is an effective and cost-effective strategy to reduce the risk of neonatal sepsis. CONTROLLED CLINICAL TRIAL REGISTER: ISRCTN29313500.

Ethnic differences in determinants of participation and non-participation in prenatal screening for Down syndrome: a theoretical framework.

OBJECTIVE: To develop a theoretical framework for analysing ethnic differences in determinants of participation and non-participation in prenatal screening for Down syndrome. METHODS: We applied Weinstein's Precaution Adoption Process (PAP) Model to the decision of whether or not to participate in prenatal screening for Down syndrome. The prenatal screening stage model was specified by reviewing the empirical literature and by data from seven focus group interviews with Dutch, Turkish and Surinamese pregnant women in the Netherlands. RESULTS: We identified 11 empirical studies on ethnic differences in determinants of participation and non-participation in prenatal screening for Down syndrome. The focus group interviews showed that almost all stages and determinants in the stage model were relevant in women's decision-making process. However, there were ethnic variations in the relevance of determinants, such as beliefs about personal consequences of having a child with Down syndrome or cultural and religious norms. DISCUSSION: The prenatal screening stage model can be applied as a framework to describe the decision-making process of pregnant women from different ethnic backgrounds. It provides scope for developing culturally sensitive, tailored methods to guide pregnant women towards informed decision-making on participation or non-participation in prenatal screening for Down syndrome.

Undergoing prenatal screening for Down's syndrome: presentation of choice and information in Europe and Asia.

To date, studies assessing whether the information given to people about screening tests facilitates informed choices have focussed mainly on the UK, US and Australia. The extent to which written information given in other countries facilitates informed choices is not known. The aim of this study is to describe the presentation of choice and information about Down's syndrome in written information about prenatal screening given to pregnant women in five European and two Asian countries. Leaflets were obtained from clinicians in UK, Netherlands, Spain, Italy, Czech Republic, China and India. Two analyses were conducted. First, all relevant text relating to the choice about undergoing screening was extracted and described. Second, each separate piece of information or statement about the condition being screened for was extracted and then coded as either positive, negative or neutral. Only Down's syndrome was included in the analysis since there was relatively little information about other conditions. There was a strong emphasis on choice and the need for discussion about prenatal screening tests in the leaflets from the UK and Netherlands. The leaflet from the UK gave most information about Down's syndrome and the smallest proportion of negative information. By contrast, the Chinese leaflet did not mention choice and gave the most negative information about Down's syndrome. Leaflets from the other countries were more variable. This variation may reflect cultural differences in attitudes to informed choice or a failure to facilitate informed choice in practice. More detailed studies are needed to explore this further.

Impact of decision-making in a multidisciplinary perinatal team.

OBJECTIVES: (1) To describe the characteristics of decision-making about management of unborn infants with serious anomalies by a multidisciplinary perinatal team. (2) To evaluate the impact of multidisciplinary team discussions on the degree to which decisions about the management of unborn infants with serious anomalies are supported. (3) To evaluate the impact of the team discussions on the arguments used by physicians for their preferences concerning management. METHODS: Prospective analysis of 78 cases discussed within the multidisciplinary perinatal team of a tertiary centre by means of an anonymous one-page questionnaire with structured questions pertaining to the opinion of the responder on medical management of each case. RESULTS: We did not find systematic differences between specialties prior to the discussion of cases. However, discussion with the multidisciplinary perinatal team improved decision-making about management of unborn infants with serious anomalies by enhancing the degree of support for the decisions taken. The discussions of the team did not change the physicians' arguments mentioned for their preferences. CONCLUSION: Multidisciplinary team discussions improve decision-making about management of unborn infants with serious congenital anomalies.

Screening in women's health, with emphasis on fetal Down's syndrome, breast cancer and osteoporosis.

Screening tests have become increasingly popular in women's health care over the last two decades. The initiative for screening is typically generated by either an agency or the health care professional being consulted for some reason. In many instances, however, the demand for screening tests is patient driven with the health care provider being poorly prepared to determine the usefulness of screening. This review illustrates the complexity of screening using three disorders where early detection and treatment have the potential to improve the quality and longevity of life. Prenatal diagnosis of Down's syndrome does not offer the parents the opportunity for cure but does offer the opportunity for education and rational choice as the impact of the diagnosis on the family is weighed. The evidence for breast cancer screening is more persuasive for older than younger women, but even in older women, there is a balance of risks and benefits. Treatment options for osteoporosis have improved in terms of reductions in fracture risk as well as beneficial effects on bone density, but evidence of the effectiveness of a screening programme for this condition in an unselected population is lacking. Ultimately, it is crucial that women be provided with clear and comprehensive information about the screening programme, in terms of possible gains but also costs of various kinds: physical, economic and psychological.

Combined first trimester screening for trisomy 21: lack of agreement between risk calculation methods.

OBJECTIVE: To call attention to differences in first trimester risk estimates for trisomy 21, as calculated by two different software packages. METHODS: A total of ninety-four pregnant women who had a first trimester risk assessment for trisomy 21 that was based on maternal age, biochemical analysis and a nuchal translucency (NT) measurement. Two commonly used software packages were used for the estimation of individual risks (i.e. Wallac-Perkin-Elmer software and Fetal Medicine Foundation software). RESULTS: Risk estimates derived from each software programme were strikingly different. In each case the discrepancy in reported magnitude of risk resulted from disparities between the two calculation methods for the assessment of the individual risk for trisomy 21. The disparities in risk estimates can be explained by significant differences in reported likelihood ratios for biochemical analyses (P = 0.01), NT measurements (P < 0.0001) and both screening parameters combined P = 0.003). CONCLUSION: It is illustrated that the lack of agreement between these risk calculation methods could give rise to major counselling problems. In order to avoid confusion, there is a need for estimating individual risks of trisomy 21 in a standardized way. It is proposed to select a set of parameters that have a proven track record as judged by detection and false positive rates and then use that set exclusively, while simultaneously monitoring its performance.