First-trimester maternal serum PAPP-A and free-beta subunit human chorionic gonadotropin concentrations and nuchal translucency are associated with obstetric complications: a population-based screening study (the FASTER Trial)

Factors associated with nonanomalous stillbirths: the Utah Stillbirth Database 1992-2002

OBJECTIVE

This study was undertaken to characterize risk factors associated with nonanomalous stillborn (SB) infants and to ascribe the probability of fetal survival by gestational age among high-risk pregnancies.

STUDY DESIGN

We compiled a database of all SB infants and an equivalent number of controls using information obtained from Utah Birth and Fetal Death Certificates during the years 1992 through 2002. Adjusted and unadjusted odds ratios for risk factors associated with SB were generated. Cox proportional hazard models were used to generate survival curves comparing pregnancies complicated by chronic hypertension or gestational hypertension with those of controls.

RESULTS

Infants with major anomalies were eliminated from both cases and controls, to generate 1566 nonanomalous SBs and 2720 nonanomalous controls. In a logistic regression model controlling for multiple maternal and fetal factors, placental abruption, hydramnios, cord prolapse, and essential hypertension were associated with an increased risk of SB. In pregnancies complicated by essential hypertension, the survival curve diverged from that of controls at those gestational ages approaching term (hazard ratio 2.24; 95% CI 1.52-3.32).

CONCLUSION

SB in nonanomalous infants in Utah is more common among pregnancies complicated by placental abruption, hydramnios, cord prolapse, and essential hypertension.

Prediction of pregnancy complications by first-trimester maternal serum PAPP-A and free beta-hCG and with second-trimester uterine artery Doppler

BACKGROUND

Previous studies have shown an association between low first trimester maternal serum free beta-hCG and PAPP-A and subsequent development of pregnancy complications. Similarly, uterine artery Doppler in the late second trimester has shown that high impedance to flow is associated with increased risk for preeclampsia and fetal growth restriction. The objective of this study is to determine whether there is an association between the maternal serum concentration of PAPP-A and free beta-hCG at 11-13(+6) weeks with the uterine artery pulsatility index (PI) at 22-24 weeks, and secondly, to compare the screening characteristics of the two methods in the prediction of adverse pregnancy outcome.

METHODS

Maternal serum PAPP-A and free beta-hCG at 11-13(+6) weeks and uterine artery PI at 22-24 weeks were measured in 4390 women with singleton pregnancies. Pregnancies with chromosomal defects or fetal anomalies were excluded. The biochemical and Doppler measurements were compared between those with normal outcome and those resulting in spontaneous preterm delivery, pre-eclampsia and fetal growth restriction (FGR). Detection rates using a combination of the biochemical and Doppler measurements were investigated.

RESULTS

In the pregnancies resulting in pre-eclampsia (n = 64) and FGR (n = 172), the median PAPP-A was lower (0.844 and 0.813 MoM), the median uterine artery mean PI was higher (1.56 and 1.18) but the median free betahCG was not significantly different (0.923 and 0.933 MoM) than in the normal outcome group. In the preterm delivery group (n = 159), the median free beta-hCG (0.944 MoM) and uterine artery mean PI (1.06) were not significantly different from normal but the median PAPP-A (0.928 MoM) was significantly lower than normal. In screening for pre-eclampsia, the detection rate, for a 5% false-positive rate, was 14.1% for PAPP-A, 54.7% for uterine artery mean PI and 62.1% for a combination of PAPP-A and uterine artery mean PI.

CONCLUSION

Maternal serum PAPP-A at 11-13(+6) of gestation is significantly lower in adverse pregnancy outcomes. The combination of first trimester serum PAPP-A and uterine artery mean PI at 22-24 weeks improves the screening efficacy for the prediction of pre-eclampsia.

First-trimester maternal dried blood Down syndrome screening marker levels in early pregnancy loss

OBJECTIVE

To determine the association of free beta hCG and PAPP-A measured during first-trimester Down syndrome risk assessment with early pregnancy loss when blood is drawn prior to scheduled ultrasound.

METHODS

Maternal dried blood samples were collected prior to the ultrasound exam for Down syndrome risk assessment. Free beta hCG and PAPP-A levels in 55 patients who experienced loss of pregnancy prior to their scheduled ultrasound appointment were compared to 6464 control pregnancies using logistic regression.

RESULTS

Low levels of free beta hCG and PAPP-A were associated with increased risk of early pregnancy loss. The detection rate of early pregnancy loss for a fixed 5% false-positive rate using free beta alone, PAPP-A alone and a combination of the two were 47, 36 and 49%, respectively.

CONCLUSION

Free beta hCG and PAPP-A can identify pregnancies at increased risk for early pregnancy loss. More studies are needed to determine whether further evaluation of these pregnancies prior to the scheduled ultrasound is warranted.

Pregnancy-Associated Plasma Protein A and Alpha-fetoprotein and Prediction of Adverse Perinatal Outcome

OBJECTIVE

To describe the association between pregnancy associated plasma protein A (PAPP-A), alpha-fetoprotein (AFP) and adverse perinatal outcome.

METHODS

We conducted a multicenter prospective cohort study of 8,483 women attending for prenatal care in southern Scotland between 1998 and 2000. The risk of delivering a small for gestational age infant, delivering preterm, and stillbirth were related to maternal serum levels of PAPP-A and AFP.

RESULTS

Women with a low PAPP-A were not more likely to have elevated levels of AFP. Compared with women with a normal PAPP-A and a normal AFP, the odds ratio for delivering a small for gestational age infant for women with a high AFP was 0.9 (95% confidence interval [CI] 0.5-1.6), for women with a low PAPP-A was 2.8 (95% CI 2.0-4.0), and for women with both a high AFP and a low PAPP-A was 8.5 (95% CI 3.6-20.0). The odds ratio for delivering preterm for women with a high AFP was 1.8 (95% CI 1.3-2.7), for women with a low PAPP-A was 1.9 (95% CI 1.3-2.7), and for women with both a low PAPP-A and a high AFP was 9.9 (95% CI 4.4-22.0). These interactions were statistically significant for both outcomes (P = .03 and .04, respectively). There was a nonsignificant trend toward a similar interaction in relation to stillbirth risk. Of the women with the combination of a low PAPP-A and high AFP, 32.1% (95% CI 15.9-52.4) delivered a low birth weight infant.

CONCLUSION

Low maternal serum levels of PAPP-A between 10 and 14 weeks and high levels of AFP between 15 and 21 weeks gestation are synergistically associated with adverse perinatal outcome.

LEVEL OF EVIDENCE

II-2.

Ultrasound and fetal diagnosis

PURPOSE OF REVIEW

The purpose of this review is to highlight publications from the last year that have advanced the use of ultrasound in obstetrics.

RECENT FINDINGS

Anatomic examination of the fetus in the first trimester has been emphasized because it allows for early diagnosis of many conditions. The prevalence of absent nasal bone, a marker for trisomy 21, in euploid fetuses depends on ethnicity. Nasal bone hypoplasia is another marker for Down syndrome. Studies on genetic screening in the first trimester have involved various serum analytes, adjustments in timing and calculations, use in multiple gestations, and the association of extreme measurements with adverse outcomes. A first-trimester integrated screening approach, which incorporates nuchal translucency, nasal bone, crown-rump length, pregnancy-associated plasma protein-A, and free beta-human chorionic gonadotropin, has the potential to maximize detection rates of Down syndrome and trisomy 18 and minimizes the screen-positive rate. The value of combining first and second-trimester results in sequential, contingent, or integrated screening protocols has been assessed. Isolated mild ventriculomegaly (10-12 mm) may prove to be a normal variant, and the role of 'soft' ultrasound markers in genetic counseling continues to be debated. Anomaly or high-risk status detection in the second trimester has been enhanced by the use of Doppler, 3D/4D ultrasound, and magnetic resonance imaging.

SUMMARY

Imaging techniques have been critical in the development of screening methods for Down syndrome or trisomy 18 and for euploid fetuses at high risk for adverse outcomes.

Additional benefits of first trimester screening

The goal of first trimester screening for aneuploidy is to provide patients their risk assessment for fetal Down syndrome. Nonetheless, it has been noted that combined screening offers physicians and patients other important pregnancy information. For example, first trimester ultrasound results in accurate pregnancy dating and enables the early diagnosis of multiple gestations during the period when amnionicity and chorionicity is best discerned. It also detects a limited number of fetal anatomical abnormalities, affording patients time to make decisions regarding the management of their pregnancies. A cystic hygroma, one of the most powerful ultrasound markers for fetal aneuploidy, can be detected on first trimester ultrasound. An enlarged nuchal translucency may identify fetuses at risk for other adverse outcomes and for congenital heart defects. In addition, abnormal first trimester serum markers are associated with adverse pregnancy outcomes, and knowledge of these abnormalities may help with patient counseling and management.

First trimester uterine artery Doppler abnormalities predict subsequent intrauterine growth restriction

OBJECTIVE

This study was undertaken to evaluate the association between uterine artery Doppler velocimetry performed between 10 and 14 weeks gestation and intrauterine growth restriction (IUGR).

STUDY DESIGN

Uterine artery Doppler velocimetry data were collected on 1067 women enrolled in the FASTER trial at the University of Colorado site. The data were analyzed by using univariate and multivariable logistic regression analysis.

RESULTS

The uterine artery mean resistance index (RI) for the entire cohort was equal on the right and left sides (0.59 +/- 0.14). Of the 1067 women, 34.2% had unilateral or bilateral diastolic notches, 1 notch was observed in 23.8%, and bilateral notches in 10.4%. Women with a high uterine artery mean RI (> or = 75th percentile) were 5.5 times more likely to have IUGR (95% CI 1.6-18.7). There was no significant relationship between notching and IUGR.

CONCLUSION

Elevated first trimester uterine artery mean RI is significantly associated with IUGR.

First and second trimester evaluation of risk for fetal aneuploidy: the secondary outcomes of the FASTER Trial

The FASTER Trial was a multicenter National Institute of Child Health and Human Development sponsored study of Down syndrome screening in a large unselected obstetric population using first and second trimester maternal serum markers and first trimester nuchal translucency sonography. The following paper will describe the FASTER Trial. It will review the outcomes of pregnancies complicated by cystic hygroma and the FASTER Trial's findings regarding first trimester nasal bone ultrasonography and screening for aneuploidy. Although the study's first and foremost goal was to compare various first and second trimester methods of screening for Down syndrome, the FASTER Trial has revealed a wealth of information not only on screening for aneuploidy but also on other obstetric issues.

First trimester Down syndrome screening: public health implications

Down syndrome (DS) screening has been an integral part of routine prenatal screening for the last three decades. Recent efforts have been directed at developing additional non-invasive prenatal screening techniques that could not only improve sensitivity of prenatal screening, but also be employed in the first trimester to offer earlier diagnostic and interventional opportunities. Nuchal translucency has proven to be an effective and cost-effective screening test that, when combined with serum markers (hCG and pregnancy-associated plasma protein [PAPP-A]) in the first and/or second trimester, broadens the diagnostic possibilities and improves the diagnostic capabilities of current prenatal DS screening methods. Despite the potential benefits, significant operational issues regarding access to and availability of such testing may limit its widespread application and necessitates the maintenance of both non-sonographic and second trimester screening methods. The implementation of first trimester DS testing requires the development and maintenance of nationally standardized quality control systems to ensure the reliability of serum and ultrasound measurements and the accurate assessment of risk. Future efforts to improve prenatal screening should continue to emphasize the need for improved access to all aspects of prenatal care, stress the importance of provider education and the necessity for extensive patient counseling, and reinforce the role of patient education and choice.

Quad Screen as a Predictor of Adverse Pregnancy Outcome

OBJECTIVE

To estimate the effect of second-trimester levels of maternal serum alpha-fetoprotein (AFP), human chorionic gonadotrophin (hCG), unconjugated estriol (uE3), and inhibin A (the quad screen) on obstetric complications by using a large, prospectively collected database (the FASTER database).

METHODS

The FASTER trial was a multicenter study that evaluated first- and second-trimester screening programs for aneuploidy in women with singleton pregnancies. As part of this trial, patients had a quad screen drawn at 15-18 6/7 weeks. We analyzed the data to identify associations between the quad screen markers and preterm birth, intrauterine growth restriction, preeclampsia, and fetal loss. Our analysis was performed by evaluating the performance characteristics of quad screen markers individually and in combination. Crude and adjusted effects were estimated by multivariable logistic regression analysis. Patients with fetal anomalies were excluded from the analysis.

RESULTS

We analyzed data from 33,145 pregnancies. We identified numerous associations between the markers and the adverse outcomes. There was a relatively low, but often significant, risk of having an adverse pregnancy complication if a patient had a single abnormal marker. However, the risk of having an adverse outcome increased significantly if a patient had 2 or more abnormal markers. The sensitivity and positive predictive values using combinations of markers is relatively low, although superior to using individual markers.

CONCLUSION

These data suggest that components of the quad screen may prove useful in predicting adverse obstetric outcomes. We also showed that the total number and specific combinations of abnormal markers are most useful in predicting the risk of adverse perinatal outcome.