Positive serum screening for fetal Down syndrome does not predict adverse pregnancy outcome in absence of fetal aneuploidy

False-Positive Maternal Serum Screens in the Second Trimester as Markers of Placentally Mediated Complications Later in Pregnancy: A Systematic Review and Meta-Analysis

BACKGROUND

Multiple-marker, maternal serum screening (MSS) has been the cornerstone of prenatal diagnosis since the 1980s. While combinations of these markers are used to predict fetal risk of Down syndrome and other genetic conditions, there is some evidence that individual markers may also predict nongenetic pregnancy complications, particularly those related to placental dysfunction. The objective of this meta-analysis was to investigate the utility of false-positive, second-trimester MSS for Down syndrome as a marker of placentally mediated complications amongst singleton pregnancies globally.

METHODS

Electronic searches of PubMed, Medline, Embase, CINAHL, Web of Science, Scopus, and grey literature to 2019 were performed to identify observational studies comparing risk of pregnancy complications amongst pregnancies with false-positive MSS versus controls. A random-effects model of pooled odds ratios by outcome of interest (stillbirth, preeclampsia, fetal growth restriction, and preterm birth) and subgrouped by type of MSS test (double-, triple-, and quadruple-marker MSS) was used.

RESULTS

16 studies enrolling 68515 pregnancies were included. There were increased odds of preeclampsia (OR 1.28, 95% CI 1.09-1.51) and stillbirth (OR 2.46, 95% CI 1.94-3.12) amongst pregnancies with false-positive MSS. There was no significant association with preterm birth or growth restriction.

CONCLUSIONS

There is some evidence of an association between false-positive, second-trimester MSS for Down syndrome and increased odds of preeclampsia and stillbirth. Future large-scale prospective studies are still needed to best determine the predictive value of false-positive MSS as a marker of placentally mediated complications later in pregnancy and evaluate potential clinical interventions to reduce these risks.

MANAGEMENT OF REDUCED FETAL MOVEMENTS

Reduced fetal movement (RFM) is commonly defined as any reduction in maternal perception of fetal activity. Perceived fetal activity may be movement of limbs, trunk or head movement, but excludes fetal hiccoughs (as this is involuntary movement). The perception of fetal movement by an expectant mother is the first, and ongoing, non-sonographic indicator of fetal viability. The “normal” pattern of fetal movements varies from pregnancy to pregnancy, and often does not become established until 28 weeks’ gestation. Many babies have particularly active periods of the day, usually corresponding to periods of maternal rest and inactivity (which may in itself reflect increased maternal awareness of fetal movement). A variable percentage of sonographically observed fetal movements are perceived by prospective mothers (commonly 30–40%, although some studies report rates as high as 80%).

Serum screening with Down's syndrome markers to predict pre-eclampsia and small for gestational age: systematic review and meta-analysis

Background

Reliable antenatal identification of pre-eclampsia and small for gestational age is crucial to judicious allocation of monitoring resources and use of preventative treatment with the prospect of improving maternal/perinatal outcome. The purpose of this systematic review was to determine the accuracy of five serum analytes used in Down's serum screening for prediction of pre-eclampsia and/or small for gestational age.

Methods

The data sources included Medline, Embase, Cochrane library, Medion (inception to February 2007), hand searching of relevant journals, reference list checking of included articles, contact with experts. Two reviewers independently selected the articles in which the accuracy of an analyte used in Downs's serum screening before the 25^th gestational week was associated with the occurrence of pre-eclampsia and/or small for gestational age without language restrictions. Two authors independently extracted data on study characteristics, quality and results.

Results

Five serum screening markers were evaluated. 44 studies, testing 169,637 pregnant women (4376 pre-eclampsia cases) and 86 studies, testing 382,005 women (20,339 fetal growth restriction cases) met the selection criteria. The results showed low predictive accuracy overall. For pre-eclampsia the best predictor was inhibin A>2.79MoM positive likelihood ratio 19.52 (8.33,45.79) and negative likelihood ratio 0.30 (0.13,0.68) (single study). For small for gestational age it was AFP>2.0MoM to predict birth weight < 10^th centile with birth < 37 weeks positive likelihood ratio 27.96 (8.02,97.48) and negative likelihood ratio 0.78 (0.55,1.11) (single study). A potential clinical application using aspirin as a treatment is given as an example.

There were methodological and reporting limitations in the included studies thus studies were heterogeneous giving pooled results with wide confidence intervals.

Conclusion

Down's serum screening analytes have low predictive accuracy for pre-eclampsia and small for gestational age. They may be a useful means of risk assessment or of use in prediction when combined with other tests.

Second trimester total human chorionic gonadotropin, alpha-fetoprotein and unconjugated estriol in predicting pregnancy complications other than fetal aneuploidy

OBJECTIVE

To assess the value of alpha-fetoprotein (AFP), total human chorionic gonadotropin (ThCG) and unconjugated estriol in predicting certain complications of pregnancy other than fetal aneuploidy.

STUDY DESIGN

Among 2384 women that underwent biochemical screening between 15 and 22 weeks of gestation, pregnancy outcome was evaluated in 677 women under 35 years of age according to serum marker levels by using cut-off points discriminative for Down syndrome or neural tube defect (NTD).

RESULTS

High alpha-fetoprotein levels (MoM>/=2.0) were found to be significantly more frequent (P<0.05) in cases of fetal growth restriction (odds ratio=2.7), miscarriage (odds ratio=4.4) and intrauterine fetal death (odds ratio=5.8). High chorionic gonadotropin levels (MoM>/=2.02) were associated with intrauterine growth restriction (odds ratio=2.1; P<0.05), miscarriage (odds ratio=4; P<0.01), preterm birth (odds ratio=2.5; P<0.05), and intrauterine fetal death (odds ratio=4.2; P<0.01). Among pregnancies with intrauterine growth restriction and threatening preterm delivery, low unconjugated estriol levels (MoM</=0.74) were significantly more frequent (odds ratio=2.2; P<0.05 and odds ratio=2.6; P<0.01, respectively).

CONCLUSION

All three markers predictive for fetal trisomy 21 shown to be associated with various pregnancy complications in euploid pregnancies.

False positive serum biochemical screening and subsequent fetal loss in women less than 35 years of age

OBJECTIVE

To examine the fetal loss rate in women younger than 35 years of age following a false positive serum biochemical screening.

DESIGN

Retrospective analysis of case records between 1991 and 1998.

SETTING

Fetal medicine unit of a large teaching hospital.

POPULATION

Four hundred and fifty-six women with singleton pregnancies and false positive serum biochemical screening for Down's Syndrome (study group). Nine hundred and twelve matched controls with true negative serum biochemical screening (control group).

METHODS

Women of both groups had a second trimester serum screening for Down's Syndrome using alpha fetoprotein, human chorionic gonadotrophin (hCG) and unconjugated oestriol (uE3); and they also underwent genetic amniocentesis.

RESULTS

The overall fetal loss rate in the study group was 5.3% (24/456), compared with 1.65% (15/912) in the control group RR 3.2, 95% CI 1.7-5.99; P < 0.001). The majority of fetal losses in the study group occurred after 28 weeks, while in the controls this happened between 24 and 28 weeks of gestation.

CONCLUSIONS

A false positive serum biochemical screening in women under 35 years of age is associated with a threefold increased risk of subsequent fetal loss. However, most of fetal losses in this group occurred after 28 weeks, indicating that intensive antepartum fetal surveillance could improve the perinatal outcome.