Screening for adverse pregnancy outcome at early gestational age

Clinical Application of a Graphene Oxide-Based Surface Plasmon Resonance Biosensor to Measure First-Trimester Serum Pregnancy-Associated Plasma Protein-A/A2 Ratio to Predict Preeclampsia

Background

Preeclampsia, a major cause of adverse pregnancy outcomes, involves metalloproteinases pregnancy-associated plasma protein (PAPP)-A and PAPP-A2 from placental trophoblasts. The graphene oxide (GO)-based surface plasmon resonance (SPR) biosensor has higher sensitivity, affinity, and selective ability than the traditional SPR biosensor. The aim of this study was to explore the feasibility of measuring first-trimester serum PAPP-A/PAPP-A2 ratio as a novel predictor of preeclampsia using the GO-SPR biosensor.

Methods

This prospective case-control study of pregnant women was conducted at MacKay Memorial Hospital, Taipei, Taiwan between January 2018 and June 2020. The SPR angle shifts of first-trimester serum PAPP-A, PAPP-A2, and PAPP-A/PAPP-A2 ratio measured using the GO-SPR biosensor were compared between preeclampsia and control groups.

Results

Serum samples from 185 pregnant women were collected, of whom 30 had preeclampsia (5 early-onset; 25 late-onset). The response time between the antibody-antigen association and dissociation only took about 200 seconds. The SPR angle shift of PAPP-A in the preeclampsia group was significantly smaller than that in the control group (median (interquartile range): 5.33 (4.55) versus 6.89 (4.10) millidegrees (mDeg), P = 0.008). Conversely, the SPR angle shift of PAPP-A2 in the preeclampsia group was significantly larger than that in the control group (5.70 (3.81) versus 3.63 (2.38) mDeg, P < 0.001). Receiver operating characteristic (ROC) curve analysis revealed a cut-off PAPP-A/PAPP-A2 ratio to predict all preeclampsia of ≤ 0.76, with an area under the ROC curve (AUC) of 0.79 (95% CI 0.73-0.85, P < 0.001). Sub-group analysis revealed a cut-off PAPP-A/PAPP-A2 ratio to predict early-onset preeclampsia of ≤ 0.53 (AUC 0.99, 95% CI 0.96-1.00, P < 0.001), and ≤ 0.73 to predict late-onset preeclampsia (AUC 0.75, 95% CI 0.68-0.81, P < 0.001).

Conclusion

Measuring first-trimester serum PAPP-A/PAPP-A2 ratio using the GO-SPR biosensor could be a valuable method for early prediction of preeclampsia.

A retrospective cohort study on the effects of Down's screening markers and maternal characteristics on pregnancy outcomes in preeclampsia

BACKGROUND

To investigate the effects of down's screening markers and maternal characteristics on preeclampsia (PE) pregnancy outcome during early and middle pregnancy.

METHODS

A retrospective study of a cohort of 246 PE and 18,709 No-PE pregnant women who participated in Down's screening during early and middle pregnancy was performed. Clinical data of pregnancy-related were collected. Multivariate binary logistic regression was used to analyze the adjusted odds ratio (aOR) and 95% confidence interval (CI) of Down's screening markers, maternal characteristics, pregnancy outcome, and other related variables, and to evaluate the influencing factors of each indicator on PE. P < .05 was considered to be statistically significant.

RESULTS

Compared with the non-PE group, the concentration and median multiple (MoM) of pregnancy-associated plasma protein-A (PAPP-A) and free beta subunit of human chorionic gonadotropin (free β-hCG) in PE group were both lower (P < .001). Multivariate binary logistic regression analysis showed that low birth weight, hydronephrosis, premature delivery, fetal growth retardation, cesarean section, live birth, hyperlipemia, infection, decreased free β-hCG and first trimester maternal weight were risk factors for PE (aOR were: 7.552, 6.684, 4.154, 3.762, 3.612, 2.454, 1.757, 1.562, 1.270, and 1.077, respectively), while uterine scar, premature rupture of membranes and elevated PAPP-A were protective factors of PE (aOR were: 0.222, 0.328 and 0.612, respectively).

CONCLUSION

Decreased maternal serum PAPP-A level, increased free β-hCG, hyperlipemia, premature delivery, cesarean section, live birth, hydronephrosis, fetal growth retardation, low birth weight, and infection are risk factors for PE, while uterine scar and premature rupture of membrane are protective factors for PE.

First-trimester biomarkers and the risk of cerebral palsy

BACKGROUND

Cerebral palsy (CP) is the most common severe motor disability and a manifestation of early brain damage.

AIMS

To analyze if abnormal levels of first-trimester biomarkers were associated with CP. Furthermore, to investigate their clinical applicability in early predicting of CP.

STUDY DESIGN

Nationwide cohort study.

SUBJECTS

We included 258.057 singleton live births, born during 2008-2013 with completed first-trimester assessments.

OUTCOME MEASURES

Data on beta subunit of human chorionic gonadotropin (beta-hCG), pregnancy-associated plasma protein-A (PAPP-A), nuchal translucency thickness, and biparietal diameter (BPD) were converted to multiple of the medians (MoM). Associations were analyzed by comparing mean and extreme levels between pregnancies with and without CP. All CP diagnoses were validated by trained neuropediatricians. Logistic regression was used to create an early prediction model.

RESULTS

The mean beta-hCG value was significantly lower in pregnancies with CP (0.96MoM [95% CI 0.91-1.02] vs 1.04MoM [1.04-1.04], p = 0.01) and the mean PAPP-A value tended to be lower (0.96MoM [0.91-1.01] vs 1.01MoM [1.00-1.01], p = 0.07). Moreover, fetuses that developed CP more likely had a BPD measurement below the fifth percentile (7.5% vs 5%, p = 0.045). The final prediction model had poor discrimination.

CONCLUSIONS

Pregnancies with CP tend to have lower values of beta-hCG and PAPP-A in the first trimester, however, the associations are mediated differently. Nonetheless, abnormal levels of the most common first-trimester biomarkers only have weak associations with CP; resulting in inadequate predictive abilities when included in an early prediction model.

Singleton pregnancy losses before gestational week 22 among patients with autoimmune disorders and Methylenetetrahydrofolate reductase polymorphisms

BACKGROUND

The rates of pregnancy losses (PLs) are increased by maternal risk factors such as autoimmune disorders (AD) and methylenetetrahydrofolate reductase (MTHFR) gene polymorphisms.

OBJECTIVE

To evaluate singleton PLs before gestational week (gw) 22 among patients with AD and MTHFR polymorphisms.

METHODS

Totally, 1108 singleton pregnancies in 243 women were categorized as: 1) 148 pregnancies in 33 patients with AD, 2) 316 pregnancies in 66 patients with MTHFR polymorphisms, 3) 644 pregnancies in 144 patients with AD +MTHFR polymorphisms. PLs were classified into subgroups: a) Chemical Pregnancy(CP), b) Blighted Ovum(BO), c) gw ⩽ 10, d) gw11-14 e) gw15-22, f) Ectopic Pregnancy(EP), g) Trophoblastic Disease(TD). Obstetric histories were compared using Beksac Obstetrics Index (BOI): [number of living child + (π/10)]/gravida.

RESULTS

PL rates before gw22 were 39.2% (58/148), 33.2% (105/316), and 36.3% (234/644) in AD, MTHFR, and AD +MTHFR groups, respectively (p= 0.421). The rate of Pre-Prenatal Screening Period fetal losses (CP + BO + gw ⩽ 10 fetal losses + EP + TD) were 84.8%, 75.9%, and 77.8% in AD, MTHFR, and AD +MTHFR, respectively (p= 0.264). Gravidity ⩽ 4 versus those with gravidity ⩾ 5 had statistically significant differences in BOI (p< 0.001).

CONCLUSIONS

PL rate before gw22 among singleton pregnancies with AD and/or MTHFR polymorphisms was 35.8%. The clinical findings seem to be more complicated in patients with gravidity ⩾ 5.

Simultaneous Real-Time Detection of Pregnancy-Associated Plasma Protein-A and -A2 Using a Graphene Oxide-Based Surface Plasmon Resonance Biosensor

Background

Pregnancy-associated plasma protein-A and -A2 (PAPP-A and -A2) are principally expressed in placental trophoblasts and play a critical role in the regulation of fetal and placental growth. PAPP-A2 shares 45% amino acid similarity with PAPP-A. This study aimed to investigate the efficacy of real-time detection of PAPP-A and PAPP-A2 using a novel surface plasmon resonance (SPR) biosensor based on graphene oxide (GO).

Methods

Traditional SPR and GO-based SPR chips were fabricated to measure PAPP-A and PAPP-A2 concentrations. We compared SPR response curves of PAPP-A and PAPP-A2 between traditional SPR and GO-SPR biosensors. We also performed interference tests and specificity analyses among PAPP-A, PAPP-A2, and mixed interference proteins.

Results

The time to detect PAPP-A and PAPP-A2 was about 150 seconds with both traditional SPR and GO-SPR biosensors. Approximately double SPR angle shifts were noted with the GO-SPR biosensor compared to the traditional SPR biosensor at a PAPP-A and PAPP-A2 concentration of 5 μg/mL. The limit of detection of the GO-SPR biosensor was as low as 0.5 ng/mL for both PAPP-A and PAPP-A2. Interference testing revealed that almost all of the protein bonded on the GO-SPR biosensor with anti-PAPP-A from the mixture of proteins was PAPP-A, and that almost no other proteins were captured except for PAPP-A2. However, the SPR signal of PAPP-A2 (5.75 mdeg) was much smaller than that of PAPP-A (13.76 mdeg). Similar results were noted with anti-PAPP-A2, where almost all of the protein bonded on the GO-SPR biosensor was PAPP-A2. The SPR signal of PAPP-A (5.17 mdeg) was much smaller than that of PAPP-A2 (13.94 mdeg).

Conclusion

The GO-SPR biosensor could distinguish PAPP-A and PAPP-A2 from various mixed interference proteins with high sensitivity and specificity. It could potentially be used to measure PAPP-A and PAPP-A2 in clinical blood samples during pregnancy.

Placental development and function in trisomy 21 and mouse models of Down syndrome: Clues for studying mechanisms underlying atypical development

Down syndrome (DS) is the most common genetic disorder leading to developmental disability. The phenotypes associated with DS are complex and vary between affected individuals. Placental abnormalities in DS include differences in cytotrophoblast fusion that affect subsequent conversion to syncytiotrophoblast, atypical oxidative stress/antioxidant balance, and increased expression of genes that are also upregulated in the brains of individuals with Alzheimer's disease. Placentas in DS are prematurely senescent, showing atypical evidence of mineralization. Fetuses with DS are especially susceptible to adverse obstetric outcomes, including early in utero demise, stillbirth and growth restriction, all of which are related to placental function. The placenta, therefore, may provide key insights towards understanding the phenotypic variability observed in individuals with DS and aid in identifying biomarkers that can be used to evaluate phenotypic severity and prenatal treatments in real time. To address these issues, many different mouse models of DS have been generated to identify the mechanisms underlying developmental changes in many organ systems. Little is known, however, regarding placental development in the currently available mouse models of DS. Based upon the relative paucity of data on placental development in preclinical mouse models of DS, we recommend that future evaluation of new and existing models routinely include histologic and functional assessments of the placenta. In this paper we summarize studies performed in the placentas of both humans and mouse models with DS, highlighting gaps in knowledge and suggesting directions for future research.

Usefulness and reliability of cell free fetal DNA screening for main trisomies in case of atypical profile on first trimester maternal serum screening

Background

Patients with atypical values of HCG and/or PAPP-A are at higher risk of chromosomal abnormality and vascular complications of pregnancy. The performance of cfDNA in this particular population has not yet been evaluated.

Objectives

The primary objective was to evaluate the usefulness and reliability of cfDNA in screening for trisomy 21, 18 and 13 for patients with HCG < 0.25 multiple of median (MoM), HCG > 5.0 MoM and/or PAPP-A < 0.25 MoM, PAPP-A > 2.5 MoM. The secondary objective was to evaluate the contribution of cfDNA assay for the prediction of pregnancy’s vascular complications.

Method

Between June 2016 and July 2017, we analysed a women cohort from all over France who had at least one first trimester serum biomarker outside of normal range, in a retrospective, observational and multicentre study. Patients were included if they had a single pregnancy, normal first trimester ultrasound examination, whatever the result of the combined first trimester screening test was. The cfDNA was analysed by massive parallel sequencing technique. The accuracy of cfDNA assay was evaluated by calculation of sensitivity and specificity, and multivariate regression analysis was used to search for predictive factors for pregnancy’s vascular complications.

Results

Among the 498 patients who underwent a cfDNA assay in this context, twenty-one (4.2%) were excluded because of loss to follow-up. Out of 477, test failure occurred for four patients initially, reduced to two patients (0.4%) after redrawn. CfDNA was positive for Trisomy 21 (n = 19), Trisomy 18 (n = 6) and Trisomy 13 (n = 1) and negative in 449. The sensitivity of cfDNA assay for trisomy 21 screening was 100% (19/19) (IC 95% 82.4–100) and specificity 100% (458/458) (IC 95% 99.2–100). Among the 447 patients included for prediction of vascular complications, there were four cases of pregnancy induced hypertension and 10 cases of preeclampsia, for which no predictive factor was identified. Intra Uterine growth restriction under 5th percentile (n = 44, 9.8%) was significantly associated with a low fetal fraction (OR = 0.87, IC 95% 0.79–0.96, p = 0.006).

Conclusion

cfDNA assay is an effective and reliable tool for women with atypical profile of first trimester serum biomarkers.

Association between unexplained thickened nuchal translucency and adverse pregnancy outcomes

OBJECTIVE

To determine the association between unexplained increased nuchal translucency (INT) and adverse pregnancy outcomes.

PATIENTS AND METHODS

The prospective database of our fetal down screening project was accessed to retrieve the records with NT measurement and complete follow-up. Pregnancies with pre-existing medical diseases, fetal chromosomal or structural abnormalities were excluded. The selected pregnancies were classified into the INT groups (> 95th percentile), the normal (< 95th percentile) group.

RESULTS

Of 6026 available for analysis (INT:277; and normal: 5749), the abortion rate was significantly higher in the INT group, 18/277 (6.5%) versus 55/5749 (1.0%); p < 0.001. After excluding 73 cases ending-up with abortion, a total of 5953 women were analyzed for final pregnancy outcomes, including 260 (4.4%), and 5693 (95.6%) in the study group (INT), and the control group (normal NT), respectively. The rates of pre-eclampsia (7.3 vs. 4.1%; p: 0.018), preterm birth (12.7 vs. 8.4%; p: 0.023), fetal growth restriction (11.5 vs. 7.6%; p: 0.032), and low birth weight (16.5 vs. 10.0%; p: 0.002) were slightly, but significantly higher in the study group.

CONCLUSIONS

INT in the first trimester is associated with significantly increased risk of abortion, fetal growth restriction, preterm birth, low birth weight and pre-eclampsia.

1H NMR-based metabolomics study on the physiological variations during the rat pregnancy process

In this study, NMR-based metabolomics in combination with multivariate pattern recognition technologies were employed to evaluate the physiological variations in the Wistar rats' plasma that are induced by pregnancy on the gestational days (GDs) 11, 14, 17 and 20. Untargeted metabolomics analysis revealed some possible mechanism of physiological effects for healthy pregnancies and showed a metabolic trajectory during pregnancy process. The levels of 24 metabolites were found to change significantly throughout pregnancy in maternal plasma. These metabolite changes involved in varied kinds of metabolic pathways including synthesis of biological substances, microbial metabolism in diverse environments, protein digestion and absorption, carbohydrate metabolism, digestion and absorption, mineral absorption, and ATP (Adenosine Triphosphate)-binding cassette transporters (ABC transporters). The substantial cores of all the metabolic pathways are promoting fetal growth and development and regulating maternal physiological state. This work showed relevant metabolic pathways perturbation in the maternal plasma due to normal pregnancy and provided the physical basis of time-dependent metabolic trajectory against which disease-related maternal physiological responses may be better understood in future studies.

Fetal Nasal Bone Status In Iranian Women Undergoing First-Trimester Screening For Trisomy 21: A Review and an Observational Study

Background:

Failed visualization of the fetal nasal bone (NB) by ultrasound at 11 - 14 weeks of gestation is strongly associated with chromosomal abnormalities. Meanwhile, the incidence of the absent fetal NB in normal fetuses in the first trimester in mothers of different ethnic origins differs significantly. It is, therefore, important to assess ethnic variations in the first-trimester visualization of the fetal NB before introducing this marker into routine screening programs for aneuploidy.

Objectives:

The objectives of this study were to determine the NB length and the prevalence of the NB absence as well as calculating the likelihood ratio (LR) for the absence of the NB in normal fetuses of Iranian women undergoing first-trimester screening for trisomy 21.

Patients and Methods:

In 767 normal fetuses, the fetal profile was examined by ultrasound for the absence/presence of the NB. The NB length was also measured, and the LR for the NB absence was also determined.

Results:

The NB was absent in 2/767 (0.26%) of the fetuses. The mean length of the NB was 3.6 ± 0.69 mm for the fetuses of 11 - 14 weeks gestational age. The LR value of the absent NB was equal to 250 in the normal fetuses of the Iranian population living in the North-West provinces.

Conclusion:

The low prevalence of the NB absence in normal fetuses in the present study is compatible with the larger size of the NB in Iranian people compared to other communities. Meanwhile, the reference range of the NB length in normal Iranian fetuses was established so that basic data could be recorded for further studies regarding the absence or presence of the NB in screening for chromosomal abnormalities (Down syndrome) within the Iranian population.

Variation of ultrasound findings in the first trimester examination of recurrent cases with trisomy 21

Increased nuchal translucency (NT) is present in about 50% of cases with trisomy 21. Very often the nuchal edema evolves in hydrops fetalis until the second trimester. Furthermore, a small amount of cases with a normal NT and trisomy 21 exhibit anatomical anomalies. We present a case of a 21-year-old woman, nulliparous, with a history of one termination of pregnancy and a smoking quitter. The prenatal control was negative for TORCH. During the first trimester scan on the 13th week, the NT was found 2.7 mm, the ductus venosus Doppler was normal, and the nasal bone was present. Hydrops fetalis was present though, and the parents were advised for chorionic villus sampling (CVS), but they opted for termination of pregnancy. The molecular control by QF-PCR showed normal karyotype for 13 and 18, a male fetus, but non-dysjunction trisomy 21 was present. Parental karyotype was advised, but they refused to perform it. One year later, the couple had another pregnancy. On the 12th week scan, the NT was found 1.0 mm, the ductus venosus Doppler was normal, and the nasal bone was present, but encephalocele was also found, and the parents consented again for termination of pregnancy. The new molecular control showed the same results. This time parental karyotype was performed. The father had a normal one, whereas the mother showed reversed p11 and q13 zones in chromosome 2. Genetical consulting and prenatal cytological control was advised in before next pregnancy.

Pregnancy-associated plasma protein A (PAPP-A) and preeclampsia

Pregnancy-associated plasma protein A (PAPP-A) is a key regulator of insulin-like growth factor bioavailability essential for normal fetal development. In maternal blood, this protein increases with gestational age and then rapidly decreases after delivery. It is routinely used for Down syndrome screening in the first trimester of pregnancy, and its decrease compared to a normal pregnancy indicates an increased risk for both chromosomal anomalies and adverse pregnancy outcomes. It belongs to a group of biomarkers that predict later preeclampsia development, primarily early onset preeclampsia; however, it should be combined with a Doppler ultrasonography of the uterine artery (pulsatile index) and other biochemical and maternal factors to achieve a higher detection rate with an acceptable false positivity rate. Some studies have demonstrated an even more pronounced decrease of PAPP-A in the early second trimester of pregnancy in women who subsequently develop preeclampsia compared with women who do not develop preeclampsia. Conversely, during the last trimester of pregnancy, its concentration increases even more in patients with preeclampsia than in patients without. It is also detectable at very low levels in nonpregnant individuals, and a higher concentration indicates an adverse effect in patients with acute coronary syndromes or stable atherosclerotic disease and in patients with end-stage renal disease who are being treated with hemodialysis.

Is there any relationship between adverse pregnancy outcome and first trimester nuchal translucency measurements in normal karyotype fetuses?

AIM

This study aims to research whether there is a relationship between first trimester nuchal translucency (NT) measurements and pregnancy complications such as gestational diabetes mellitus (GDM), gestational hypertension (GHT), intrauterine growth restriction (IUGR) and oligohydramnios.

METHOD

This study included 225 singleton pregnancies attending Canakkale Onsekiz Mart University Obstetrics and Gynecology clinic for all monitoring and examinations, and gave birth at our clinic between January 2011 and December 2012. Data sources were clinical records and the hospital's automation system, and the study was planned as retrospective cohort. NT measurement was made between 10 weeks 3 days and 13 weeks 6 days gestation. For data analysis, the chi-square, Mann-Whitney U test and Spearman correlation were used.

RESULTS

Of pregnancies, in the study, 5 (2.2%) developed GDM, 6 (2.6%) developed GHT, 2 (0.89%) developed IUGR and 10 (4.4%) developed oligohydramnios. There was no correlation identified between NT measurements and development of GDM, GHT, IUGR and oligohydramnios.

CONCLUSION

There was no relationship found between first trimester NT measurements and complications that could develop in pregnancy. For the first time in the literature, NT and oligohydramnios were studied and no relationship was observed.

Is there an association between platelet count during the first trimester and preeclampsia or other obstetric complications later in pregnancy?

OBJECTIVE

To examine whether an association exists between platelet (PLT) count in the first trimester of pregnancy and the risk for hypertensive disorders or other obstetric complications.

METHODS

The study population included all registered births with available PLT count from the first trimester of pregnancy during 2000-2010. Thrombocytopenia was defined as PLT count below 100,000/μL. A comparison was performed between women with and without thrombocytopenia. Multiple logistic regression models were used to control for confounders.

RESULTS

The study population included 33,890 deliveries; of these, 119 (0.35%) were with thrombocytopenia. Women with thrombocytopenia had significantly higher rates of preterm delivery (16.0% vs. 9.4%; p = 0.015). There was no significant difference between the groups regarding hypertensive disorders.

CONCLUSIONS

Hypertensive disorders cannot be predicted based on PLT count during the first trimester of pregnancy. Nevertheless, thrombocytopenia during the first trimester is a risk factor for preterm delivery.

Can leukocyte count during the first trimester of pregnancy predict later gestational complications?

PURPOSE

To examine whether an association exists between maternal leukocyte count in the first trimester of pregnancy and the risk for development of obstetric complications.

METHODS

The study population included all the registered births (n = 33,866) with available white blood cell count (WBC) from the first trimester of pregnancy, during 2000-2010 in a tertiary medical center. The leukocyte count was sorted by the following groups: WBC < 3.5 10 × 9/l, WBC = 3.5 10 × 9/l-13.8 10 × 9/l, and WBC > 13.8 10 × 9/l. These groups were compared regarding obstetrical characteristics and perinatal outcomes. Multiple logistic regression models were used to control for confounders.

RESULTS

The study population included 33,866 deliveries, of these 0.94 % had leukocytosis WBC > 13.8 10 × 9/l. Women with leukocytosis delivered significantly earlier, were more likely to be Jewish, and in their first pregnancy. There were significantly higher rates of preterm delivery before 37 weeks, fertility treatments, hypertensive disorders, gestational diabetes mellitus, and cesarean section among these patients. There was no significant difference between the groups regarding preterm premature rupture of membranes (PPROM) and chorioamnionitis. Women with leukocytosis during the first trimester had significantly higher rates of fetuses who were small for gestational age and with birth weight <2,500 g. Multivariable analysis showed a significant association between preterm delivery before 37 weeks and leukocytosis during the first trimester of pregnancy (p = 0.003).

CONCLUSIONS

Leukocytosis during the first trimester is significantly associated with an increased risk for obstetrical complications, in particular preterm delivery. Nevertheless, further studies should focus on women with leukocytosis during the first trimester in order to verify our results.

Standardized Procedural Practices of the Ontario Prenatal Screening Program for aneuploidies and open neural tube defects

BACKGROUND/OBJECTIVES

The Ontario Prenatal Screening Program (OPSP) follows internationally recognized standardized procedures for laboratories and genetics clinics. However, it has been found that some procedures are subject to interpretation, so the current procedures are designed to facilitate a unified approach in the interpretation of literature recommendations. In Ontario, the OPSP offers multiple screening modalities with integrated prenatal screening (including both first and second trimester markers) being the most commonly chosen option. Other screening modalities include first trimester screening, second trimester quad screening, serum integrated screening, and NT-Quad.

METHODS

The standardization was based on a literature review and on current practices in Ontario.

RESULTS/DISCUSSION

The main finding of the review was a paucity of published data relating to the procedures and the decision-making processes involved in prenatal screening. The purpose of this publication is to provide the most up-to-date and pertinent information for clinical laboratory professionals involved with prenatal screening for Down syndrome, trisomy 18 and open neural tube defects.