Measurement of placental alkaline phosphatase in maternal plasma as an indicator of subsequent low birthweight outcome

Total alkaline phosphatase levels by gestational age in a large sample of pregnant women

INTRODUCTION

Total alkaline phosphatase (tALP) levels rise physiologically in maternal serum during pregnancy, and excessively so in certain conditions. However, current reference values are dated, nonlinear, and based on small samples. Factors related to variation in tALP remain unexplained. Thus, our goals in this study were to establish a physiological development curve for tALP within low-risk pregnancies and to evaluate the factors influencing tALP values.

METHODS

This was a single-center, retrospective, observational study. All patients who delivered a live singleton infant at our center from January 1, 2011 to May 31, 2019, and had a tALP assay during pregnancy, were included regardless of the gestational age at which the assay was conducted.

RESULTS

A total of 2415 pregnancies were included. Median tALP decreased during the first trimester, it increased slightly during the second trimester, and then increased sharply during the third trimester. Factors associated with a significant increase in tALP were chronic histiocytic intervillositis, cholestasis, multiple pregnancies, liver disease, preeclampsia, smoking, and low weight for gestational age. Conversely, gestational diabetes was associated with a discrete decrease in tALP.

DISCUSSION

Our large sample allowed establishment of tALP reference curves based on gestational age. To interpret these results more thoroughly, factors that influence tALP rates should be further scrutinized.

A Case of Markedly Elevated Isolated Alkaline Phosphatase in the Third Trimester of Pregnancy

Background

Alkaline phosphatase (ALP) is an enzyme produced by the liver, small intestine, bone, and kidneys as well as the placenta during pregnancy. ALP levels may increase up to twice the normal limit during pregnancy secondary to placental release and fetal bone growth. Rare case reports of extremely elevated levels of ALP during pregnancy have demonstrated possible association with adverse pregnancy outcomes.

Case

The patient is a 36-year-old G2P1001 who was found to have extremely elevated ALP levels during pregnancy after presenting with bilateral lower leg swelling and rash after receiving the Pfizer COVID-19 vaccine. She subsequently developed intrahepatic cholestasis of pregnancy and preeclampsia. ALP peaked at 2,601 U/L immediately prior to delivery at 36 weeks 1 day. She was followed postpartum, and her ALP levels had nearly normalized by 15 weeks postpartum.

Conclusion

Our case demonstrates a rare report of an extremely elevated level of ALP in the setting of multiple adverse pregnancy outcomes, including preterm delivery, preeclampsia without severe features, and intrahepatic cholestasis of pregnancy.

Does an abnormally elevated maternal alkaline phosphatase pose problems for the fetus?

We report a potential association between an abnormally raised pregnancy level of alkaline phosphatase (ALP) and intrauterine growth restriction (IUGR). There are few reports of women with abnormally high ALP during pregnancy. However, there is work to suggest an association with placental insufficiency, low birth weight and preterm delivery. In conjunction with a rising ALP, fetal IUGR and intermittent absence of umbilical artery end diastolic flow had evolved. A greatly elevated ALP may be a marker for placental insufficiency and IUGR.

Meta-regression analysis to evaluate relationships between maternal blood levels of placentation biomarkers and low delivery weight

BACKGROUND

Caution is required for women at increased risk of low neonatal delivery weight.

OBJECTIVE

To evaluate relationships between maternal placentation biomarkers and the odds of low delivery weight.

SEARCH STRATEGY

Databases including PubMed/MEDLINE were searched up to May 2017 using keywords involving biomarker names and "low birthweight."

SELECTION CRITERIA

English language studies providing true- and false-positive, and true- and false-negative results of low delivery weight classified by maternal blood levels of placentation biomarkers (in units of multiple of the mean [MoM]) were included.

DATA COLLECTION AND ANALYSIS

Coefficients representing changes in log odds ratio for low delivery weight per 1 MoM increase in maternal blood placentation biomarkers, and those adjusted for race, sampling period, and/or study quality were calculated.

MAIN RESULTS

Adjusted coefficients representing changes in log odds ratio for low delivery weight per 1 MoM increase in maternal blood levels of α-fetoprotein (AFP) and β-human chorionic gonadotropin (β-hCG) were significantly greater than 0 (both P<0.001), whereas that for pregnancy-associated plasma protein A (PAPP-A) was significantly less than 0 (P=0.028). Adjusted models explained the higher proportion of between-study variance better than non-adjusted models.

CONCLUSIONS

Elevated AFP and β-hCG, and reduced PAPP-A in maternal blood were positively associated with odds of low delivery weight.

Maternal Blood Biomarkers of Placentation to Predict Low-Birth-Weight Newborns: A Meta-Analysis

OBJECTIVE

The development of methods for pre-delivery prediction of low-birth-weight newborns would be clinically advantageous because low birth weight contributes to a high infant mortality rate. This study was performed to examine whether maternal blood biomarkers of placentation can be used to predict low-birth-weight newborns.

METHODS

Ten databases, including PubMed/Medline, were searched. Any English language study that provided all of the true- and false-positive and true- and false-negative results of this prediction was included in the analysis. Study quality was assessed using the Quality Assessment of Diagnostic Accuracy Studies. Bivariate diagnostic meta-analysis was performed to construct hierarchical summary receiver operating characteristic curves.

RESULTS

Based on relatively good quality studies, alpha fetoprotein (AFP), human chorionic gonadotropin (hCG), and pregnancy-associated plasma protein A (PAPP-A) (n = 73, 19, and 7, respectively) showed low sensitivity and specificity and low diagnostic odds ratio. The informational usability was categorized as "no exclusion or confirmation" (i.e., positive likelihood ratio <10 and negative likelihood ratio >0.1). The diagnostic accuracy of AFP and hCG or PAPP-A was categorized as low (i.e., 0.5 ≤ area under the curve ≤0.7) or could not be categorized (i.e., area under the curve <0.5).

CONCLUSION

There is no evidence that maternal blood levels of AFP, hCG, or PAPP-A used as a single predictor are useful to predict low-birth-weight newborns.

Tobacco smoking leads to extensive genome-wide changes in DNA methylation

Environmental factors such as tobacco smoking may have long-lasting effects on DNA methylation patterns, which might lead to changes in gene expression and in a broader context to the development or progression of various diseases. We conducted an epigenome-wide association study (EWAs) comparing current, former and never smokers from 1793 participants of the population-based KORA F4 panel, with replication in 479 participants from the KORA F3 panel, carried out by the 450K BeadChip with genomic DNA obtained from whole blood. We observed wide-spread differences in the degree of site-specific methylation (with p-values ranging from 9.31E-08 to 2.54E-182) as a function of tobacco smoking in each of the 22 autosomes, with the percent of variance explained by smoking ranging from 1.31 to 41.02. Depending on cessation time and pack-years, methylation levels in former smokers were found to be close to the ones seen in never smokers. In addition, methylation-specific protein binding patterns were observed for cg05575921 within AHRR, which had the highest level of detectable changes in DNA methylation associated with tobacco smoking (–24.40% methylation; p = 2.54E-182), suggesting a regulatory role for gene expression. The results of our study confirm the broad effect of tobacco smoking on the human organism, but also show that quitting tobacco smoking presumably allows regaining the DNA methylation state of never smokers.

Potential biochemical markers for preterm labor: a pilot study in north India

Preterm delivery is a major contributor for neonatal mortality. Intensive research is underway to establish a reliable biomarker that can ascertain the risk of preterm delivery in pregnant women. The aim of our study was to evaluate the role of various biochemical parameters as potential biomarker for risk assessment for preterm labor. Forty women presenting with preterm labor and 40 women who delivered at term were included in the study. Parameters that were evaluated include corticotrophin (ACTH), prolactin, thyroid stimulating hormone (TSH), ferritin and Alkaline Phosphatase (ALP). Serum ACTH, ferritin, ALP and Ferritin/Iron ratio were significantly higher in the subjects who delivered prematurely as compared to the controls. Comparison of sensitivity, specificity, likelihood ratio, positive and negative predictive values for different cut offs for ACTH, ferritin, ALP and ferritin/iron ratio was carried out. Ferritin emerged as the best marker with area under curve of 0.96 as compared to 0.88 for ACTH, 0.825 for ALP and 0.735 for ferritin/iron ratio. Our study establishes the superiority of ferritin as a predictive biomarker for preterm labor as compared to the rest of the parameters evaluated.

Biochemical diagnosis of placental infarction/damage: acutely rising alkaline phosphatase

There are currently no simple tests in clinical use to detect acute placental damage. A case is described to demonstrate that a routinely used measurement such as alkaline phosphatase (ALP) can be employed to detect acute damage to the placenta. Seventeen serial blood samples, three pre-delivery, were collected from a 22-year-old primigravida who delivered a stillborn baby. Retrospectively, blood samples were analysed for total and heat-stable ALP as well as human chorionic gonadotropin (hCG) and alpha-fetoprotein (AFP) as a measure of placental function when an unusual pattern of change in ALP was noticed. Histological examination of the placenta revealed new and old placental infarcts. Total and heat-stable ALPs as well as AFP peaked by more than eight-, 19- and two-fold, respectively over 16 h. Plasma hCG fell sharply even before delivery of placenta by five-fold over 16 h before further falling slowly to baseline. The fall in hCG is also consistent with the placental damage being acute and critical. As far as we are aware this is the first description of changes in circulating proteins reflecting placental damage.

The Preterm Prediction Study: the value of serum alkaline phosphatase, alpha-fetoprotein, plasma corticotropin-releasing hormone, and other serum markers for the prediction of spontaneous preterm birth

OBJECTIVE

High levels of a number of analytes are found in maternal blood; alkaline phosphatase,alpha-fetoprotein, and corticotropin-releasing hormone have been associated with spontaneous preterm birth. We investigated the relationship between 8 potential blood markers and subsequent spontaneous preterm birth in asymptomatic pregnant women.

STUDY DESIGN

We performed a nested case control study that involved 127 women who were enrolled in the preterm prediction study and who had a singleton spontaneous preterm birth at <35 weeks and 127 women who had a term birth and served as matched (age, parity, center) controls. Serum that was collected at 24 and 28 weeks was analyzed for alkaline phosphatase, alpha-fetoprotein, corticotropin-releasing hormone, and 5 other analytes.

RESULTS

Alkaline phosphatase, alpha-fetoprotein, and corticotropin-releasing hormone, but not other analytes, were significantly elevated in pregnancies that ended in spontaneous preterm birth. For alkaline phosphatase at 24 weeks, the odds ratio for spontaneous preterm birth at <32 weeks was 6.8 (range, 1.4-32.8) and for spontaneous preterm birth at <35 weeks 5.1 (range, 1.7-15.6). Similar results were found at 28 weeks. For alpha-fetoprotein at 24 weeks, the odds ratio for spontaneous preterm birth at <32 weeks was 8.3 (range,2.2-30.9) and for spontaneous preterm birth at <35 weeks was 3.5 (range, 1.8-6.7). The levels at 28 weeks were still predictive but less so than at 24 weeks. Corticotropin-releasing hormone, at 28 weeks but not at 24 weeks, was predictive for spontaneous preterm birth at <35 weeks, with an odds ratio 3.4 (range, 1.0-10.9).

CONCLUSION

Elevated alkaline phosphatase and alpha-fetoprotein are associated with subsequent spontaneous preterm birth in asymptomatic pregnant women at 24 and 28 weeks. Elevated corticotropin-releasing hormone levels at 28 weeks are associated with spontaneous preterm birth at <35 weeks.

Maternal serum urea resistant alkaline phosphatase in Down syndrome pregnancy

BACKGROUND

The normal levels of alkaline phosphatase (AP) activity in maternal serum are virtually the same as those observed in Down syndrome (DS) pregnancies at 14-20 weeks' gestation. Using urea inhibition of AP, we observed an atypical AP isoenzyme in the neutrophils of mothers with trisomy 21 fetuses.

AIM

To assess the use of urea as a selective inhibitor of serum AP in order to seek a possible diagnostic difference between normal and DS pregnancies.

STUDY DESIGN AND SUBJECTS

Serum AP samples from 24 DS pregnancies and 204 control cases were examined at 12-22 weeks' gestation with and without 2.5 M urea AP inhibition at 18 degrees C for 2 h. The levels of AP activity obtained without urea and the percentage urea AP inhibition were analyzed in the two groups.

RESULTS

Without urea treatment, no significant difference of total alkaline phosphatase activity levels was detected between the 204 normal controls and the 24 DS samples. Using 2.5 M urea AP inhibition, after 120 min of exposure at 18 degrees C, the residual activity, as a percentage of initial values of AP, showed significantly higher resistance in the DS samples (> or = 50 IU/l of total AP activity) at 15-22 weeks' gestation. However, at 12-14 weeks (< or = 45 IU/l of total AP activity), no significant difference was found between the DS and control cases.

CONCLUSION

Serum urea resistant alkaline phosphatase in DS pregnancies showed a significant difference only at 15-22 weeks' gestation, compared with normal controls.

Placental alkaline phosphatase, insulin, and adenine nucleotides or adenosine synergistically promote long-term survival of serum-starved mouse embryo and human fetus fibroblasts

Earlier we showed that in serum-starved fibroblasts placental alkaline phosphatase (PALP) can exert growth factor-like effects. Here we report that in mouse embryo (NIH 3T3) and human fetus (HTB-157) fibroblasts, PALP (200 nM) alone provided full protection against serum starvation-induced cell death for 5 days. After 12 days, substantial effects of PALP on cell survival required the copresence of insulin (500 nM) and ATP or adenosine (100 microM). In serum-starved NIH 3T3 cells, PALP induced activating phosphorylation of p42/p44 mitogen-activated protein (MAP) kinases; insulin, but not ATP, had small additional effects. PALP also stimulated the expression of various cyclins; ATP both prolonged and enhanced PALP-induced expression of cyclins A and E. Finally, ATP/adenosine enhanced activation of Akt kinase by insulin. The results suggest that PALP may be a regulator of growth and remodeling of fetal tissues during the second and third trimester of pregnancy when it is expressed.

Heat-stable and immunoreactive placental alkaline phosphatase in maternal serum from Down's syndrome and trisomy 18 pregnancies

Placental alkaline phosphatase (ALP) activity was investigated in second-trimester maternal sera from 37 pregnancies with Down's syndrome, 28 pregnancies with trisomy 18, and in a series of 497 controls using a fluorimetric heat inactivation assay and specific immunoassay. After conversion of individual analyte values to multiples of the normal gestational median (MOM), no significant differences in total or placental ALP activities were found in the trisomy 21 or trisomy 18 cases (P > 0.01). In the Down's syndrome pregnancies, total ALP activity was 0.93 MOM, heat-stable ALP activity was 1.09 MOM, and placental ALP (by immunoassay) 0.96 MOM. In the trisomy 18 cases, total ALP activity was 0.90 MOM, heat-stable ALP activity was 0.79 MOM, and placental ALP (by immunoassay) 0.94 MOM. We conclude that neither total nor placental ALP activity is a useful marker for Down's syndrome or trisomy 18 screening.

Maternal serum placental alkaline phosphatase level and risk for preterm delivery

OBJECTIVE

The purpose of this study was to determine whether elevated midtrimester serum placental alkaline phosphatase levels are predictive of preterm delivery.

STUDY DESIGN

By use of banked serum specimens from a sample of women who had received maternal serum alpha-fetoprotein screening, placental alkaline phosphatase values for multiples of the median were obtained from 270 mothers who had experienced a preterm delivery and from 1598 mothers of term, appropriate-for-gestational-age infants. Specimens were analyzed for placental alkaline phosphatase by means of a monoclonal antibody enzyme-linked immunosorbent assay. Logistic regression was used to determine whether placental alkaline phosphatase was associated with preterm birth, while potential confounders were controlled for.

RESULTS

Women with placental alkaline phosphatase levels > or = 2.0 multiples of the median were significantly more likely to be delivered of a preterm infant in the current pregnancy compared with women with levels < 2.0 multiples of the median (odds ratio 2.9, 95% confidence interval 2.1 to 3.9). The likelihood of preterm birth increased significantly with higher multiples of the median (p < 0.001).

CONCLUSION

Women with elevated placental alkaline phosphatase levels are at increased risk for preterm delivery. Additional studies are needed to evaluate the clinical utility of placental alkaline phosphatase testing as a means of identifying mothers at risk for preterm birth.

Biology of human alkaline phosphatases with special reference to cancer

The current information on the cloning and sequencing of four alkaline phosphatase genes (PLAP, GCAP, IAP, TNAP) has been reviewed. It has provided insights into their evolutionary history and the mechanisms of catalysis and of uncompetitive inhibition. The oncodevelopmental biology of the germ cell and its excessive GCAP eutopic expression in neoplasia are noted, and there is reason to suggest that the enzyme may serve to guide migratory cells and to transport specific molecules such as fat and immunoglobulins across membranes. The hyperexpression of all four genes has been observed in various human tumors and in their cell lines, particularly cancers of the testis and ovary. The membrane APs have been investigated as targets for immunolocalization and immunotherapy.

First-trimester maternal serum biochemical indicators in Down syndrome

A set of 21 early maternal serum samples (19 first-trimester and two at 14 weeks) from pregnancies resulting in a child with Down syndrome was matched for gestation and length of storage with 63 samples from unaffected pregnancies. The concentrations of alpha-fetoprotein (AFP), unconjugated oestriol (uE3), human chorionic gonadotrophin (hCG), pregnancy-specific beta 1-glycoprotein (SP1), and placental alkaline phosphatase (PALP) were measured. The ratios of the medians for Down syndrome pregnancies compared with the medians for controls were AFP 0.71, uE3 0.67, hCG 1.43, SP1 0.79, and PALP 0.92. Although the differences between the medians for affected and unaffected pregnancies were not significant, the trends for AFP, uE3, and hCG confirm earlier findings on first-trimester samples.