Assay of a placental protein to determine fetal risk

Assessing hypoxic damage to placental trophoblasts by measuring membrane viscosity of extracellular vesicles

INTRODUCTION

As highly sophisticated intercellular communication vehicles in biological systems, extracellular vesicles (EVs) have been investigated as both promising liquid biopsy-based disease biomarkers and drug delivery carriers. Despite tremendous progress in understanding their biological and physiological functions, mechanical characterization of these nanoscale entities remains challenging due to the limited availability of proper techniques. Especially, whether damage to parental cells can be reflected by the mechanical properties of their EVs remains unknown.

METHODS

In this study, we characterized membrane viscosities of different types of EVs collected from primary human trophoblasts (PHTs), including apoptotic bodies, microvesicles and small extracellular vesicles, using fluorescence lifetime imaging microscopy (FLIM). The biochemical origin of EV membrane viscosity was examined by analyzing their phospholipid composition, using mass spectrometry.

RESULTS

We found that different EV types derived from the same cell type exhibit different membrane viscosities. The measured membrane viscosity values are well supported by the lipidomic analysis of the phospholipid compositions. We further demonstrate that the membrane viscosity of microvesicles can faithfully reveal hypoxic injury of the human trophoblasts. More specifically, the membrane of PHT microvesicles released under hypoxic condition is less viscous than its counterpart under standard culture condition, which is supported by the reduction in the phosphatidylethanolamine-to-phosphatidylcholine ratio in PHT microvesicles.

DISCUSSION

Our study suggests that biophysical properties of released trophoblastic microvesicles can reflect cell health. Characterizing EV's membrane viscosity may pave the way for the development of new EV-based clinical applications.

Second-trimester maternal serum markers in the prediction of preeclampsia

AIM

To determine whether late second-trimester maternal serum biomarkers are useful for the prediction of preeclampsia during the third trimester, a case-control study including 33 preeclamptic and 71 healthy pregnancies was conducted. Maternal serum concentrations of placental protein 13 (PP13), pregnancy-associated plasma protein (PAPP-A), pentraxin3 (PTX3), soluble FMS-like tyrosine kinase-1 (sFlt-1), myostatin and follistatin-like-3 (FSLT-3) were measured at 24-28 weeks' gestation. All the concentrations of these markers were compared between the preeclamptic and control groups. Receiver operating characteristic (ROC) curve analysis was applied to assess sensitivity and specificity of serum markers with significant difference.

RESULTS

The levels of PP13 and sFlt-1 were significantly increased and FSLT3 was significantly decreased in patients with preeclampsia. However, the concentration of PAPPA, PTX3 and myostatin did not differ significantly. In screening for preeclampsia during the third trimester by PP13, sFlt-1 and FSLT3, the detection rate was 61.3%, 48.1% and 39.1%, respectively, at 80% specificity, and the detection rate increased to 69.8% by combination of these three markers.

CONCLUSION

Maternal serum levels of PP13, sFlt-1 and FSLT3 play an important role in predicting late-onset preeclampsia, and the combination of these three markers significantly increases the detection rate for prediction.

The relationship between first-trimester pregnancy-associated plasma protein-A levels and intrapartum fetal distress development

OBJECTIVE

To investigate the relationship between the development of intrapartum fetal distress and serum pregnancy-associated plasma protein-A (PAPP-A) levels measured during first-trimester aneuploidy screening tests.

MATERIAL AND METHODS

This retrospective study included 283 uncomplicated pregnancies that resulted in full-term live births via spontaneous labor or with the induction by oxytocin. Cases were divided into two groups based on whether their first-trimester PAPP-A multiple of the median (MoM) levels were ≤0.5 (Group 1, n=75) or >0.5 (Group 2, n=208). As primary end points, the rate of cesarean section (C/S), the rate of C/S due to fetal distress, and the umbilical artery blood pH values in cases of C/S for fetal distress were compared between the two groups. Statistical analyses were performed using the Chi-square test and independent samples t-test. P≤0.05 were considered statistically significant.

RESULTS

The mean gestational age at birth and the birth weights were significantly lower in Group 1 than in Group 2 (p=0.002 and p=0.007, respectively). Although the rate of C/S was similar between the groups (p=0.823), the rate of C/S due to fetal distress was significantly higher in Group 1 than in Group 2 (68.4% vs. 42%, respectively; p=0.050) and the mean umbilical artery blood pH value for C/S deliveries indicated by fetal distress was lower (p=0.048) in Group 1 than in Group 2. When the mode of delivery was analyzed according to the application of labor induction, both the C/S delivery rates (31.6% in Group 1 and 31.7% in Group 2; p=0.992) and C/S delivery rates due to fetal distress (66.7% in Group 1 and 46.2% in Group 2; p=0.405) were similar in both groups.

CONCLUSION

Low PAPP-A levels (≤0.5 MoM) in the first trimester are associated with the risk of intrapartum fetal distress development and the likelihood of C/S for fetal distress. Nonetheless, this risk is not affected by labor induction.

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.

Circulating predictive biomarkers in preeclampsia

The aim of the paper was to review promising prediction biomarkers for preeclampsia. The methods included review of abstracts on PubMed, using "preeclampsia", "biomarker", "prediction" as key words, followed by review of primary papers investigating blood based biomarkers. Angiogenic factors, such as PlGf and sFlt1, and PP13 seem presently to have the best predictive test values for preeclampsia, but sensitivity and specificity is still too low to prove useful in a population screening setting. Biomarker testing should still be part of research protocols. Biomarkers could provide useful in selecting high-risk women for prophylactic trials as well as identifying pregnancies that could profit from closer follow-up.

Novel biomarkers for predicting preeclampsia

Preeclampsia is a major cause of maternal morbidity and mortality worldwide. Despite decades of research into the condition, the ability of clinicians to predict preeclampsia prior to the onset of symptoms has not improved significantly. In this review, we will examine the pathophysiology underlying preeclampsia and will look at potential biomarkers for early prediction and diagnosis. In addition, we will explore potential future areas of research into the condition.

Nuchal translucency as a predictor of adverse pregnancy outcome

BACKGROUND

Thickened nuchal translucency (NT) has been related to fetal genetic syndromes, structural abnormalities, and other diseases. The aim of this research was to evaluate the association of NT with adverse pregnancy outcomes.

STUDY DESIGN

In the period 2002-2004 in 2104 pregnant women between 10+6 and 13+5 weeks' gestation, NT was evaluated as a parameter for aneuploidy screening: out of these, 734 singleton pregnant women that underwent 2nd trimester amniocentesis and whose pregnancy outcome were known were selected. NT was statistically correlated to pregnancy and neonatal outcome.

RESULTS

Median gestational age (GA) at NT evaluation was 11+2 weeks' gestation. NT median was 1.1 mm (0.9-1.4 mm, 25th-75th centile, range 0.5-4.0 mm). After multiple logistic regressions, the variables significantly associated to NT values were: threatened preterm labor (p<0.008) and preterm labor (p<0.02). The best diagnostic accuracy point was NT>95th centile and >1.5 MoM for the prediction of threatened preterm labor.

CONCLUSION

In this series, increased NT values were associated to threatened preterm labor and preterm labor in euploid fetuses: this finding may have clinical consequences in the management of such pregnancies.

Prediction of pre-eclampsia by uterine artery Doppler ultrasonography and maternal serum pregnancy-associated plasma protein-A, free beta-human chorionic gonadotropin, activin A and inhibin A at 22 + 0 to 24 + 6 weeks' gestation

OBJECTIVE

To investigate the potential value of combining uterine artery Doppler ultrasonography with the measurement of maternal serum pregnancy-associated plasma protein-A (PAPP-A), free beta-human chorionic gonadotropin (beta-hCG), activin A and inhibin A at 22 + 0 to 24 + 6 weeks' gestation, in the prediction of pregnancies that subsequently develop pre-eclampsia.

METHODS

The maternal serum PAPP-A, free beta-hCG, activin A and inhibin A concentrations at 22 + 0 to 24 + 6 weeks' gestation were measured in samples obtained from women with singleton pregnancies who participated in a screening study for pre-eclampsia by transvaginal color flow Doppler measurement of the uterine artery pulsatility index (PI). A search was made of the database to identify those who subsequently developed pre-eclampsia (n = 24) and a group of controls with normal outcome (n = 144). Regression analysis was performed to establish any relationship between the biochemical markers themselves and between the biochemical markers and uterine artery mean PI. A multivariate Gaussian model combining various biochemical markers with uterine artery mean PI was developed using standard statistical modeling techniques and the performance of such models in discriminating cases with pre-eclampsia was evaluated by receiver-operating characteristics curve (ROC) analysis.

RESULTS

In the pre-eclampsia group, compared to the controls, the uterine artery mean PI and the maternal serum levels of PAPP-A, free beta-hCG, activin A and inhibin A were significantly increased. The predicted detection rates of pre-eclampsia, for a false positive rate of 5%, was 50% by uterine artery mean PI, 5% by PAPP-A, 10% by free beta-hCG, 35% by inhibin A and 44% by activin A. Screening by a combination of uterine artery mean PI and maternal serum activin A and inhibin A could detect 75% and 92% of patients who subsequently developed pre-eclampsia, for false positive rates of 5% and 10%, respectively.

CONCLUSION

Screening for pre-eclampsia by uterine artery PI at 22 + 0 to 24 + 6 weeks' gestation can be improved by measurement of activin A and inhibin A levels.

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.

Quantitative distribution of a panel of circulating mRNA in preeclampsiaversus controls

OBJECTIVE

The aim of this study was to evaluate whether the quantitative distribution of a panel of circulating mRNAs from maternal whole blood of normal pregnancies is statistically different from those complicated with preeclampsia (PE) with or without intrauterine growth restriction (IUGR).

METHODS

Maternal whole blood of six subjects with mild or severe PE with or without IUGR and 30 matched controls (1:5 match for gestational age) were retrospectively examined for circulating mRNA markers. Seven specific mRNA markers were identified and chosen based on previous microarray mRNA expressions performed on placental tissue from normal and PE patients. They were human placental lactogen (hPL), inhibin A, KISS-1, pregnancy-associated plasma protein-A (PAPP-A), plasminogen activator inhibitor type 1 (PAI-1), selectin-P and vascular endothelial growth factor receptor (VEGFR), which were therefore quantified for statistical purposes.

RESULTS

Median gestational age was 229 (178-283) and 232 (194-262) days for controls and cases respectively. All mRNA markers but PAPP-A, showed statistically different median values. They were hPL, inhibin A, KISS-1, PAI-1, Selectin-P, and VEGFR. Inhibin A, Selectin-P and VEGFR showed higher values than expected for controls. Instead, hPL, KISS-1 and PAI-1 values of PE patients were lower than those of controls. Selectin-P was the marker with the most aberrant difference, followed by VEGFR and KISS-1.

CONCLUSION

This preliminary analysis revealed that the median values of a panel of mRNAs from the maternal blood of PE patients were different from those of the same gestational age control group at the third trimester. If prospective studies at the second trimester could detect a related marker sufficiently able to discriminate between affected and unaffected patients and thus detect the disease before its clinical onset, then a screening project using a panel of mRNAs would be feasible.

First trimester screening for trisomy 21

OBJECTIVE

To assess the value of first trimester maternal serum free beta human chorionic gonadotropin (beta hCG), pregnancy-associated plasma protein (PAPP-A) concentrations and nuchal translucency (NT) as predictors of pregnancy complications.

DESIGN

A retrospective collaborative study of beta hCG, PAPP-A and NT between 10 and 14 weeks of pregnancy in patients in whom pregnancy was followed to term. Nuchal translucency, maternal serum PAPP-A and free beta hCG concentrations were measured in 1779 women with singleton pregnancies and without aneuploidies. Individual values were expressed as multiple of medians (MoM). Normal and abnormal pregnancies were compared for these parameters.

RESULTS

Irrespective of the presence or absence of pregnancy-associated pathologies; there was no change in the median MoM for NT. The median MoM for free beta hCG was significantly increased in women with threatened abortions whereas the median MoMs for PAPP-A in women with spontaneous abortions or with pre-term deliveries were decreased significantly compared to normal pregnancies. These parameters have however no clinical usefulness as determined by receiver operator characteristics curves.

CONCLUSION

Since PAPP-A is a protease that specifically degrades insulin-like growth factor binding proteins we would conclude that the control of the insulin-like growth factor system in the first trimester of pregnancy might play a key role in determining subsequent pregnancy outcome.

Women with preeclampsia have increased serum levels of pregnancy-associated plasma protein A (PAPP-A), inhibin A, activin A and soluble E-selectin

OBJECTIVE

Poor placentation in early pregnancy is thought to lead to an excessive maternal systemic inflammatory response, which causes the maternal syndrome of preeclampsia. The aims of this retrospective study were to confirm old reports of increased blood levels of pregnancy-associated plasma protein A (PAPP-A) in preeclampsia and how its levels correlate with the levels of other placental and endothelial proteins that are reported to be elevated in preeclampsia.

METHODS

Nineteen women with preeclampsia symptoms were matched with 19 normal pregnant controls for gestational age, maternal age, and parity. PAPP-A, placental pregnancy-specific beta1-glycoprotein (SP1), inhibin A, activin A, and sE-selectin were measured in serum using specific ELISAs.

RESULTS

Maternal serum levels of PAPP-A, inhibin A, activin A and sE-selectin were increased in women with preeclampsia (mean 157.7 vs. 76.85 mIU/mL, p=0.005; 3.08 vs. 1.51 ng/mL, p=0.002, 32.36 vs. 3.77 ng/mL, p<0.001 and 62.15 vs. 46.37 ng/mL, p=0.02 respectively), compared to controls. Serum levels of SP1 were not altered in preeclampsia. PAPP-A (r=0.636, p<0.01) had a positive correlation with sE-selectin in patients with preeclampsia. Serum inhibin A and activin A had a significant positive correlation with each other in preeclampsia.

CONCLUSIONS

Raised levels of PAPP-A in preeclampsia confirm earlier reports. Activin A showed the highest increase over the controls and is thus likely to be a better serum marker for this pathology than the other markers that were tested.

Decreased first trimester PAPP-A is a predictor of adverse pregnancy outcome

OBJECTIVE

Low levels of maternal serum pregnancy associated plasma protein-A (PAPP-A) have been linked to chromosome anomalies such as trisomy 21, 13 and 18, triploidy and sex chromosome aneuploidy. Low levels of PAPP-A have also been implicated in spontaneous miscarriage. The purpose of this study was to evaluate whether low levels of first trimester PAPP-A are predictive of other adverse pregnancy outcomes.

STUDY DESIGN

The study included patients with singleton pregnancies who underwent combined first trimester screening using nuchal translucency (NT) and maternal serum free beta-human chorionic gonadotrophin (free beta-hCG) and PAPP-A at 10-13 weeks' gestation. Patients with chromosome aberrations or fetal anomalies were excluded. Serum marker levels were expressed as gestational age-specific multiples of the median (MoMs). The incidences of various adverse pregnancy outcomes (spontaneous preterm labor, fetal growth restriction (FGR), proteinuric and non-proteinuric pregnancy induced hypertension (PIH), intrauterine fetal demise, oligohydramnios, spontaneous miscarriage and placental abruption) were evaluated, according to maternal PAPP-A MoM levels.

RESULTS

Of the 1622 patients in the study, pregnancy complications were observed in 184 (11.3%). Patients with PAPP-A < or =0.25 MoM had significantly higher rates of FGR (RR = 3.12), proteinuric PIH (RR = 6.09), spontaneous miscarriage (RR = 8.76). No statistically significant differences were noted for other adverse outcomes evaluated Women with PAPP-A < or =0.50 MoM also had significantly higher rates of FGR (RR = 3.30) and spontaneous miscarriage (RR = 3.78).

CONCLUSIONS

We conclude that decreased levels of first trimester maternal serum PAPP-A are predictive not only of chromosome anomalies but also of adverse pregnancy outcome.

Maternal serum levels of free beta-hCG and PAPP-A in the first trimester of pregnancy are not associated with subsequent fetal growth retardation or preterm delivery

The purpose of this case-control study was to examine the association of first-trimester concentrations of free beta-human chorionic gonadotropin (free beta-hCG) and pregnancy-associated plasma protein A (PAPP-A) in maternal serum with subsequent preterm delivery or small-for-gestational age (SGA) fetuses. We collected all the blood samples before chorionic villus sampling in the first trimester. Concentrations of free beta-hCG and PAPP-A were expressed in multiples of the median (MOM) for gestational age. We compared the levels of both analytes in 73 SGA pregnancies (birth weight below the fifth percentile) with those in 292 normal controls, who were matched for gestational age, maternal age, parity, maternal weight, and smoking habits. We also compared the levels in 87 pregnancies with a preterm delivery (delivery before 37 completed weeks) with those in 348 matched controls. The median concentrations of PAPP-A and free beta-hCG, expressed in MOMs, in the 73 SGA pregnancies were 0.83 and 0.95, respectively, compared with 0.98 and 1.01, respectively, in the 292 matched controls (P=0.08 and 0.19, respectively). In the 87 pregnancies with a preterm delivery, the median concentrations of PAPP-A and free beta-hCG were 0.98 and 0.94, respectively, compared with 0.99 and 0.99, respectively, in the 348 matched controls (P=0.82 and 0.10, respectively). In contrast with the maternal serum analytes used in second-trimester screening--alpha-fetoprotein and human chorionic gonadotropin--this study showed that concentrations of PAPP-A and free beta-hCG in the first trimester were not associated with subsequent fetal growth retardation or preterm delivery.

CA 125 levels in abruptio placentae

The diagnosis of abruptio placentae is frequently difficult despite ultrasonography; additional diagnostic parameters would be useful. Maternal serum CA 125, which is believed to derive from the decidua, is elevated in the first trimester and immediately after delivery when placental separation occurs, possibly because of decidual disruption. Serum CA 125 was measured in 27 patients beyond 20 weeks' gestation who were first seen with vaginal bleeding and in 17 control patients of similar gestational age and labor status. Mean (+/- SD) CA 125 levels were higher (p less than 0.01) among patients with abruptio placentae (105.9 +/- 115 U/ml) than among those with alternate sources of bleeding (13.7 +/- 10 U/ml) or control patients (18.2 +/- 11.7 U/ml). Mean (+/- SD) serum CA 125 levels in seven control patients within 6 hours post partum (194 +/- 80.5 U/ml) were higher than those among patients first seen with abruptio placentae (p less than 0.01). Sensitivity and specificity of CA 125 for abruptio placentae were 70% and 94%, respectively. Our data support a decidual source for CA 125 and may indicate utility of CA 125 as a marker for abruptio placentae.

Antenatal assessment of the fetus

There is now a complex array of genetic, biochemical, and biophysical parameters to use in our assessment of the unborn. This article reviews these various parameters and discusses the indication for their use, as well as their limitations.

Current concepts in management of obstetric problems for pediatricians. I. Monitoring the high-risk fetus

Modern pediatric/neonatal practice demands an understanding of fetal monitoring. Biochemical techniques have given way to biophysical and ultrasonographic modalities in an attempt to improve both sensitivity and specificity. Simple techniques such as fetal movement counts show promise and are being investigated.

Placental protein measurements in complicated pregnancies. I. Intrauterine growth retardation

Maternal serum levels of human placental lactogen (hPL), schwangerschaftsprotein 1 (SP1) and pregnancy-associated plasma protein A (PAPP-A) were measured serially throughout pregnancy in 753 women who had a normal pregnancy when recruited during the second trimester. Thirty-three women were delivered of an infant with low birth-weight and with phenotypic features of intrauterine growth retardation (IUGR). The predictive value of an abnormal (less than 10th centile) hPL result (PVpos) in the identification of IUGR was between 28 and 32%, the sensitivity (36-54%) being greatest at 35 weeks gestation. The predictive value of a normal result (PVneg) was 87-96% at various stages of pregnancy, also greatest at 35 weeks gestation. For SP1, the sensitivity and predictive values were also greatest at 35 weeks gestation (PVpos, 20%; sensitivity, 32%; PVneg, 95%), but for PAPP-A these values were considerably less at all gestations. The trends in levels of hPL, SP1 and PAPP-A observed in individual patients with IUGR were not apparently related to any clinically recognizable feature of the pregnancy or the degree of fetal compromise, irrespective of whether the levels were within or outside the 80% confidence limits of the normal range or whether the levels fell from within the normal range. These data suggest that maternal hPL measurements are superior in the identification of IUGR in samples obtained at 30-35 weeks gestation.

Placental protein measurements in complicated pregnancies. III. Premature labour

Maternal serum levels of pregnancy-associated plasma protein. A (PAPP-A), human placental lactogen (hPL) and schwangerschafts-protein 1 (SP1) were measured serially during second and third trimester in 753 women with normal pregnancy when they were recruited to the study. In 24 women spontaneous premature labour occurred before 37 completed weeks and these women had significantly lower mean levels of serum SP1 at 29-31 weeks and at 33-34 weeks gestations but similar mean levels of serum PAPP-A and hPL at all gestations compared with corresponding values in normal pregnancy. The predictive value of an abnormal SP1 result was 5.2% at 29-31 weeks and 10.3% at 33-34 weeks. Furthermore, trends of levels of the three placental proteins in individual patients were similar to those seen in normal pregnancy, and the trends were unrelated to the occurrence of other complications and the time of onset of labour. This study suggests that measurements of the three placental proteins are unlikely to be of any value in the prediction of spontaneous premature labour.

Placental protein measurements in complicated pregnancies. II. Pregnancy-related hypertension

Maternal serum levels of pregnancy-associated plasma protein A (PAPP-A), human placental lactogen (hPL) and schwangerschafts-protein 1 (SP1) were measured serially during the second and third trimesters in 753 women with a normal pregnancy when recruited during the second trimester. Thirty-seven pregnancies were complicated by pregnancy-related hypertension after 28 weeks gestation. Maternal levels of PAPP-A and SP1, and trends of levels in individual patients, could generally not be distinguished from those seen in patients with a normal pregnancy, and were unrelated to the time of onset of the disease, its severity or the occurrence of other complications with one exception, in which decreased levels of SP1 and hPL were seen. Mean levels of hPL were significantly lower (P less than 0.05) at 35 weeks gestation. These data suggest that the measurement of the placental proteins examined here is of no value in the prediction of occurrence of pregnancy-related hypertension.

Serum PAPP-A in normal pregnancy: relationship to fetal and maternal characteristics

Pregnancy associated plasma protein A (PAPP-A) was measured in maternal serum by electroimmunoassay in 414 women (with subsequent normal pregnancy outcome) during the 38th week of pregnancy. PAPP-A levels were examined in relation to maternal and fetal characteristics, revealing a statistically significant relationship with maternal weight, placental weight, fetal sex and gravidity. The correlation of PAPP-A levels to fetal sex and gravidity could not be explained by differences in placental or maternal weight. Mean levels of PAPP-A were also not significantly different in relation to fetal sex.

An ELISA for pregnancy-associated plasma protein A

An enzyme-linked immunoassay for pregnancy-associated plasma protein A is described. The assay is sensitive (7.6 IU/l) and precise (overall CV varied between 8.9% and 10.8%). Recovery was 100% over the working range. Parallel behaviour was observed between the International Reference Preparation 78/610 and pregnancy serum, thus allowing calibration of a laboratory standard pool against IRP 78/610.

Effect of anticoagulants on the measurement of pregnancy-associated plasma protein-A (PAPP-A)

The level of pregnancy-associated plasma protein-A (PAPP-A) in blood measured by rocket immunoelectrophoresis is affected by the addition of anticoagulants. When compared with levels in serum, those in heparin and sequestrene plasmas were higher, while those in sodium citrate, acid citrate dextrose and fluoride oxalate plasmas were lower. Similar results were obtained when the anticoagulants were added to serum and the effect on the measured level was dose-dependent within limits. Addition of anticoagulants to serum affected the mobility of PAPP-A in crossed immunoelectrophoresis, but this was not necessarily in keeping with the effect on rocket height. Addition of sodium chloride to serum did not influence the measured levels of PAPP-A.

Specific and reversible interaction between pregnancy-associated plasma protein A and heparin

An interaction between heparin and circulating pregnancy-associated plasma protein A (PAPP-A) has been observed. This interaction could be reversed by the addition of the specific heparin antagonist protamine sulphate. In the presence of heparin, crossed immunoelectrophoretic analysis revealed an alteration in the electrophoretic mobility of PAPP-A, while a significant increase (22 to 64 per cent, P less than 0.02) in measured levels of PAPP-A was seen in electroimmunoassays. These findings are discussed in relation to the optimal conditions for the precise measurement of PAPP-A.

Pregnancy-associated plasma protein A in the prediction of early pregnancy failure

Maternal circulating pregnancy-associated plasma protein A (PAPP-A) was measured in 51 patients with vaginal bleeding in the first half of pregnancy. Concentrations of PAPP-A were consistently lower in pregnancies which failed. In the prediction of early pregnancy failure, the predictive value of depressed maternal PAPP-A levels was 58%, the sensitivity was 91.9%, and specificity was 95.1%. These results compared favorably with other biochemical tests of placental function. However, if fetal life was demonstrated ultrasonically, depressed levels of PAPP-A substantially differentiated between those pregnancies which continued normally and those which did not, suggesting that PAPP-A estimations would be of clinical value in cases previously beyond the reach of any diagnostic measure.

Studies on the concentration of pregnancy-associated plasma protein-A during normal and complicated pregnancy

Pregnancy-associated plasma protein-A was assayed in the blood of 347 women during pregnancy, using a new primary standard of PAPP-A as reference. The protein was assayed by antibody-antigen crossed electrophoresis with the lower limit of confident assay being 9.5 micrograms PAPP-A/ml (13 pmol/ml). PAPP-A was first detected at 14 weeks of gestation; by term it had risen to within the range 20 to 320 micrograms/ml. There was an indication that pregnancies involving a male baby had higher PAPP-A levels in blood than did those involving female babies. In 51 blood samples from 30 patients with gestational diabetes (taken between 28 weeks of pregnancy and term) there was no significant alteration in PAPP-A values compared with controls. In 35 blood samples from 15 patients with insulin-dependent diabetes, levels of PAPP-A were significantly lower than in controls or in gestational diabetes. In 43 blood samples from 35 patients with babies affected with intrauterine growth retardation (between 28 weeks and term), there was no significant difference in PAPP-A levels compared with controls. The effect of insulin on the blood levels of PAPP-A suggests that the concentration of PAPP-A is capable of altering significantly in response to certain physiological changes associated with the control of carbohydrate metabolism.

Immunological studies of the human placenta: functional and morphological analysis of pregnancy-associated plasma protein A (PAPP-A)

A blood protein, pregnancy-associated plasma protein A (PAPP-A), has been isolated from the plasma of pregnant women. An antiserum to this protein has been prepared and used to localize the protein within the placenta by immunofluorescence. It was found to be inconstantly present in the syncytiotrophoblast and intervillous fibrin. Neither antiserum nor antigen exerts a cytotoxic effect on peripheral blood lymphocytes, and neither affected blastogenic responses of lymphocytes to mitogens or in mixed lymphocyte culture reactions.

Relationship of obstetric parameters to the concentration of pregnancy-associated plasma protein A

Pregnancy-associated plasma protein A (PAPP-A) was measured by rocket immunoelectrophoresis in 272 patients at 34 weeks of pregnancy and within 48 hours before delivery. The values obtained have been compared to maternal parameters (age, weight, weight gain, blood group, rhesus factor, and parity) and to fetal parameters (sex, weight, Apgar score, rhesus factor, blood group, and placental weight). Maternal age, increased parity, and increased body weight are related to decreased PAPP-A levels. On the other hand, mothers carrying male fetuses, rhesus-negative children, and babies with Apgar scores higher than 7 at 1 minute have increased PAPP-A concentrations. These findings are discussed in relation to PAPP-A's involvement in the maternal immunologic system.