Placental protein and hormone measurements in twin pregnancy

Summary. Maternal serum levels of human placental lactogen (hPL), schwangerschaftsprotein 1 (SP1), pregnancy-associated plasma protein A (PAPP-A), placental protein 5 (PP5) and total oestriol (E3) were measured serially in 35 twin pregnancies during the third trimester. Eighteen pregnancies had major complications including dysmaturity of one or both fetuses in nine, premature labour in six, and placental abruption in three. Serum levels of all five variables were higher than in singletons, this distinction being greatest for hPL and lowest for SP1 and E3. The levels of hPL, PP5 and E3 just before delivery were significantly correlated with the total birthweight, a correlation with placental weight being evident only for hPL and PP5. A significant correlation between the five biochemical variables at 33–34 weeks was only seen between hPL and PAPP-A. Protein and hormone levels in. the abnormal twin pregnancies were not apparently different from those in the normal twin pregnancies. These data suggest that only hPL levels biochemically reflect this extreme of fetal and placental growth, but that neither the levels of hPL nor any of the other biochemical indices examined are altered in abnormalities in twin pregnancy     

Measurement of plasma placental proteins and estriol in the detection of intrauterine growth retardation

This study was designed as an assessment of the clinical value of total estriol, placental lactogen (hPL), pregnancy specific glycoprotein (SP1), pregnancy-associated plasma protein-A (PAPP-A) and placental protein 5 (PP5), measured in a single sample of maternal serum, in the detection of intrauterine growth retardation (IUGR) in a large series of high risk pregnancies. Our results show the highest detection rate with SP1 (51%) and second highest with hPL (35%); estriol was less useful while PAPP-A and PP5 were of no value. However, there was 31% of false positives with SP1 compared with 14% for hPL. The best combination of the five parameters for the diagnosis of IUGR was achieved by measurement of both SP1 and hPL, with a low concentration of either protein indicating IUGR (sensitivity 63%, specificity 63%).     

The localization of pregnancy proteins (hPL, SP1 and PAPP-A) in intra- and extrauterine pregnancies

The localization of human placental lactogen (hPL), pregnancy-specific beta-1 glycoprotein (Schwangerschaftsprotein 1, SP1) and pregnancy-associated protein A (PAPP-A) was examined in intrauterine and tubal ectopic gestation (n = 5) by the immunoperoxidase technique. The distribution of hPL and SP1 was identical in placental tissues obtained from intra- and extrauterine pregnancies, being uniformly seen throughout the syncytiotrophoblast. hPL and SP1 were not demonstrated in uterine decidual tissue from ectopic pregnancies. During early (week 8) intrauterine pregnancy, PAPP-A was not restricted to the mature syncytiotrophoblast, being observed also in some trophoblast-like cells adjacent to islands of syncytiotrophoblast. In contrast, in ectopic gestation, PAPP-A was observed in these cells at six weeks' gestation only. We were unable to detect PAPP-A in trophoblastic tissue of chorionic villi and uterine decidual tissue from ectopic gestation.     

First-trimester maternal serum PAPP-A,SP1 and M-CSF levels in normal and trisomic twin pregnancies

OBJECTIVE: To study PAPP-A and SP1 for biochemical trisomy screening in twin pregnancies and to investigate the role of maternal and placental compartments in marker production by comparing the levels of the decidual cytokine M-CSF with the PAPP-A and SP1 from the placenta. METHODS: Thirteen twin pregnancies with at least one chromosomally abnormal fetus were compared with 68 normal twin pregnancies. Sera were obtained between 11 + 3 and 13 + 6 weeks of gestation, and PAPP-A, SP1 and M-CSF levels were determined by immunoassay. These concentrations were also compared with gestation-matched groups of 18 singleton normal pregnancies and 18 singleton Down syndrome pregnancies. RESULTS: PAPP-A and SP1, but not M-CSF, levels were higher in normal twin pregnancy than in normal singleton pregnancy. SP1 levels, but not PAPP-A, correlated to M-CSF. PAPP-A, but not SP1, levels were reduced in abnormal twin pregnancies, with an increasing effect according to the number of affected fetuses, and were more pronounced in pregnancies with trisomy 18 or 13 than in trisomy 21 fetuses. M-CSF was inconsistent, with a trend towards increased levels in trisomy 21. CONCLUSION: PAPP-A remains the best biochemical screening marker for fetal trisomies 21, 18 or 13, in singleton as well as in twin pregnancy. In contrast to SP1, its site of production is not likely to be restricted to the placenta. The role of the (maternally produced) M-CSF remains to be further investigated.     

Maternal serum levels of placental proteins after in vitro fertilisation and their implications for prenatal screening

OBJECTIVES: To determine whether the serum levels of pregnancy-associated plasma protein A (PAPP-A), pregnancy-specific beta(1)-glycoprotein (SP1), placental lactogen (hPL) and human chorionic gonadotrophin (hCG) are different in pregnancies obtained after in vitro fertilisation (IVF) and embryo transfer (ET) in comparison to spontaneous pregnancies. Assessment of the need to establish normal medians for biochemical trisomy screening in IVF pregnancies. METHODS: The population comprised 96 IVF-ET pregnancies, of which 79 came from fresh gonadotrophin-stimulated cycles and 17 from embryo transfers without gonadotrophin stimulation (natural cycle IVF, frozen embryo transfers), and 156 spontaneous pregnancies. A single blood sample was obtained between 7 + 0 and 16 + 3 weeks. PAPP-A, SP1, hPL and hCG were quantified and the levels compared between gonadotrophin-stimulated IVF, steroid-only- or non-stimulated IVF, and controls with respect to gestational age using non-parametric statistical analysis. RESULTS: PAPP-A and hPL levels were reduced after stimulated IVF in early gestation (before 10 pregnancy weeks); SP1 followed the same trend without reaching statistical significance. hCG tended to be increased after IVF treatment including non-gonadotrophin-stimulation cycles, and also beyond 10 pregnancy weeks. CONCLUSION: Reduced PAPP-A with increased hCG yields an increased risk in screening for foetal trisomy 21. We confirm recently published observations but do not recommend the establishment of normal medians for IVF pregnancies since the extent of the deviations is varying according to the different stimulation protocols and dosages of gonadotrophins used.     

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

Summary. 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 <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.     

Circulating levels of pregnancy proteins in early and late pregnancy in relation to placental tissue concentration.

The concentrations of human chorionic gonadotrophin (hCG), human placental lactogen (hPL), pregnancy specific beta 1 glycoprotein (SP1), ferritin (PP2) and placental protein 5 (PP5) were examined in maternal serum and placental tissue in early and late pregnancy. The circulating concentration of hPL, SP1, and PP5 were higher during late pregnancy than early pregnancy, that of hCG lower, and ferritin (PP2) levels showed no difference. Placental tissue levels of hPL and SP1 were higher in late pregnancy, hCG levels lower, and ferritin (PP2) and PP5 showed no change. The ratio of the concentration in maternal serum to that in placental tissue increased during pregnancy for all proteins with the exception of ferritin. It is proposed that the mechanism of secretion of trophoblast specific proteins varies widely and that this should be taken into account in the clinical interpretation of circulating levels in the mother.     

Circulating levels of placental proteins, placental protein 5 (PP5), placental lactogen and Schwangerschafts-protein 1 (SP1), in antepartum eclampsia

Summary. Placental protein 5 (PP5), Schwangerschaftsprotein 1 (SP1) and human placental lactogen (hPL) were measured in 36 serum samples from seven women with antepartum eclampsia. PP5 levels were generally elevated, hPL levels were reduced and SP1 levels were within the usual ranges.     

Concentration of placental protein 10 (PP10) in maternal serum and amniotic fluid throughout normal gestation and in pregnancy complicated by fetal growth retardation

PP10, a new placental glycoprotein, was studied by a specific and sensitive double-antibody radioimmunoassay in maternal serum and other body fluids throughout pregnancy. The mean value of serum PP10 in healthy nonpregnant individuals was approximately 10 microU/l. During normal pregnancy it rose to 3,500 microU/l. The rate of rise was obtained from 78 normal pregnancies with 279 single assay values from weeks 6-40. The shape of the curve resembled that for other placental proteins (HPL, SP1). PP10 levels in amniotic fluid were measured in 145 samples from weeks 13-55 of normal pregnancies and at term. The mean concentration was 500 microU/l until week 18 and then rose slowly. Cord blood contained only trace amounts. PP10 was not found in maternal urine. The concentration in maternal serum and amniotic fluid was higher in twin pregnancies than in singleton pregnancies. In 46 cases with low birth weights the PP10 levels in maternal serum were significantly lower than normal. Simultaneous measurements of PP10 and E3, HPL and SP1 were made in 17 individual follow-up's. PP10 was comparable with E3 and appeared to be better than HPL and SP1 in predicting intrauterine fetal growth retardation.     

The relationship of placental protein 14 (PP14) in the mother and fetus to specific products of the human placenta

Levels of placental protein 14 (PP14), human placental lactogen (hPL) and unconjugated oestriol (E3) were measured in maternal peripheral and umbilical arterial and venous blood obtained from 65 normal pregnancies at term delivery. PP14 levels were one order of magnitude higher in the mother than in the fetus. Neither maternal nor fetal levels of PP14 were related to the birthweight of the fetus. There was a relationship between maternal and umbilical venous levels of PP14, which suggests that fetal PP14 is derived by transfer from the mother, or that there is an independent fetal source with a control mechanism similar to that of the mother. The findings are compatible with earlier observations to the effect that PP14, in contrast to products such as hPL and E3, is not specific to the trophoblast.     

The relation between the concentration of placental specific proteins in retroplacental and peripheral blood.

Concentrations of four placental proteins: human placental lactogen (hPL), placental protein 5 (PP5), pregnancy specific beta 1 glycoprotein (SP1) and human chorionic gonadotrophin (hCG), and a normal serum component, alpha 2 macroglobulin, were measured in the peripheral circulation and in blood obtained from the retroplacental space in 20 women at term delivery. Levels of hPL and PP5 were higher in the retroplacental blood than in the peripheral circulation in all patients. By contrast, levels of SP1 and hCG were consistently lower in retroplacental blood than in the peripheral circulation. Similarly, levels of alpha 2 macroglobulin were lower in the retroplacental blood. It is suggested that this 'reverse' gradient is a technical arterfact. These findings are discussed in relation to synthesis of placental proteins in a site distal to the retroplacental space, and the introduction of a technical artefact in the collection of samples.     

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.     

Prognostic significance of the new placental proteins in trophoblastic disease

Circulating levels of four specific placental proteins, human chorionic gonadotrophin (hCG), Schwangerschafts protein 1 (SP1), placental protein 5 (PP5) and pregnancy-associated plasma protein A (PAPP-A), were measured in 31 patients with hydatidiform mole before treatment. Seven patients subsequently developed clinical choriocarcinoma and three of them had pulmonary metastases. The estimations of hCG, PP5 and PAPP-A levels were found to be of no value in the prediction of malignant sequelae. Levels of SP1 greater than or equal to 16.5 i.u./l were associated with a higher incidence of subsequent malignant disease (P less than 0.05), the risk being at least nine times greater in these patients. The predictive value of high levels of SP1 was 35%, the specificity 45.8% and sensitivity 100%.     

Second- and third-trimester serum levels of placental proteins in preeclampsia and small-for-gestational age pregnancies

BACKGROUND: Poor placentation may perpetuate preeclampsia, but the presence of a major placental pathology has been questioned in cases of preeclampsia where the newborn has an appropriate birthweight for gestational age. On the other hand, poor placentation is also observed in the absence of preeclampsia, in pregnancies with small-for-gestational-age (SGA) fetuses. In late gestation, maternal serum levels of placental protein hormones are changed in both preeclampsia and SGA, but no longitudinal pre-onset studies are available for pregnancy-associated plasma protein A (PAPP-A), pregnancy-specific beta1-glycoprotein (SP1) or human placental lactogen (HPL). METHODS: In a nested case-control study we compared maternal serum levels of PAPP-A, SP1, HPL and placenta growth factor (PLGF) at 17, 25 and 33 weeks in pregnancies developing preeclampsia without fetal growth restriction (n = 28), or characterized by a growth-retarded fetus (n = 25), with gestation-matched controls (n = 65). The proteins were quantified using microplate enzyme immunometric assays and the serum levels at 17, 25 and 33 weeks compared between the three groups by nonparametric statistical tests. RESULTS: In pregnancies with subsequent preeclampsia PAPP-A, SP1, HPL and PLGF were reduced at 17 weeks of gestation whereas at 25 and 33 weeks only PLGF remained below the controls. In growth-restricted pregnancies PAPP-A, SP1 and HPL were reduced at 17 weeks, and only HPL continued to be strongly affected thereafter. CONCLUSION: The reduced serum levels of the placental proteins PAPP-A, SP1 and HPL in the early second trimester (17 weeks) in pregnancies with subsequent preeclampsia or with fetal growth restriction involve an underlying role for the placenta in either pathology independent from the other.     

Placental protein measurements in complicated pregnancies. III. Premature labour

Summary. 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 a 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 gestation 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.     

Diagnosis and Management of Extrauterine Pregnancies

Summary: This study was based on 16 women provisionally diagnosed as having extrauterine pregnancies. Of these, 13 (81.3%) were confirmed as positive at operation. Patients were managed according to 1 of 3 regimens; 1) methotrexate (n = 4), 2) methotrexate followed by surgery (n = 3) and 3) surgery (n = 6). Serial blood samples, collected before and after treatment, were analyzed for ovarian (oestradiol, E2; progesterone, P4) uterine (placental protein 14, PP14) and placental markers (chorionic gonadotrophin, HCG; pregnancy-associated plasma protein-A (PAPP-A). Of the pretreatment samples, only 30.4% and 41.7% were depressed for PP14 and HCG, respectively. By contrast, the diagnostic value of PAPP-A (77.8%) and P4 (87.5%) was greater. Biochemical monitoring of treatment was best achieved with trophoblastic derived antigens (HCG), whereas antigens of maternal origin demonstrated widely varied responses. This study established the effectiveness of chemotherapy for treatment of tubal pregnancies as an alternative to surgery, but if a biochemical marker is required, the marker of choice is HCG.     

Monitoring of postimplantation embryo viability following successful in vitro fertilization and embryo transfer by measurement of placental proteins

Serum levels of pregnancy-associated plasma protein A (PAPP-A), human chorionic gonadotropin (hCG), and pregnancy-specific beta 1-glycoprotein (SP1) were measured in 21 women after successful in vitro fertilization and embryo transfer. Of the 21 pregnancies, 14, including 1 twin gestation, progressed successfully to term. The remaining seven, composed of tubal (n = 3), anembryonic (n = 1), and spontaneously aborted (n = 3) pregnancies, failed during the first half of pregnancy. Placental protein measurement was of no diagnostic value in the detection of anembryonic pregnancy. Similarly, measurement of hCG and SP1 could not readily distinguish tubal ectopic from normal intrauterine pregnancies. By contrast, the predictive value (38.9%) of a depressed PAPP-A level in conjunction with superior diagnostic sensitivity (70%) and relative risk factor (23.6) proved to be of greater diagnostic value in this potentially lethal condition. In the absence of ultrasonography, the biochemical diagnostic indices were comparable in the prediction of spontaneous abortion. However, in the presence of a live fetus, PAPP-A levels were consistently depressed (sensitivity, 91.7%) many weeks before pregnancy demise. The relative risk factor of depressed PAPP-A levels was 29 times greater than the risk associated with a depressed hCG level. These findings further demonstrate the potential diagnostic value of PAPP-A measurement for monitoring postimplantation embryo viability.     

Human placental lactogen is a first-trimester maternal serum marker of Down syndrome

BACKGROUND: Human placental lactogen (hPL) is synthesised by the placenta and found in maternal serum. We analysed the potential of hPL as a first-trimester maternal serum-screening marker for fetal Down syndrome (DS). MATERIALS AND METHODS: hPL was quantified by ELISA in 47 DS pregnancies and 136 controls in gestational weeks 8-13. Distributions of log multiples of the median (MoMs) were established. The quantity of hPL in DS screening was estimated using Monte Carlo simulation methods. RESULTS: The mean log10 MoM hPL was - 0.1995 (SD: 0.1993) in affected and 0.0026 (SD: 0.2129) in control pregnancies. This corresponds to a MoM of 0.63 in DS pregnancies. hPL correlated significantly with log10 MoM values of hCGbeta (r = 0.320) and PAPP-A (r = 0.590) in controls, but not with hCGbeta (r = 0.228) or PAPP-A (r = 0.090) in DS pregnancies. The inclusion of hPL in the double test (PAPP-A + hCGbeta) increased the detection rate from 67 to 75% for a false-positive rate of 5%. CONCLUSION: hPL is a DS screening marker that is applicable at weeks 9-13 and could be included in multiple marker first-trimester screening for DS.     

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

Summary. Maternal serum levels of human placental lactogen (hPL), schwangerschaftsprotein l (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 (< 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. 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.