Prognostic significance of raised serum α-fetoprotein levels in twin pregnancies

Summary. Maternal serum α-fetoprotein (AFP) was measured during the second trimester in 219 twin pregnancies uncomplicated by neural-tube defects (NTD) and in 11 twin pregnancies discordant for NTD. Serum AFP levels were recorded in multiples of the median value (MOM) calculated from normal singleton pregnancies. Of the twin pregnancies uncomplicated by NTD 49% had AFP levels <2·5 MOM, 7·8% had levels >5 MOM and 59% of these were associated with either abortion, stillbirth or fetus papyraceous. In twin pregnancies with serum AFP levels <5 MOM an unsuccessful outcome was noted in only 4% (χ², P <0·05). There was a significant negative correlation between serum AFP levels and combined birthweights (r=0·954). All 11 pregnancies discordant for NTD had serum AFP values >5 MOM and this level appears to be a suitable cut-off point above which there should be further diagnostic investigations and monitoring of fetal well-being.     

Maternal serum activin,inhibin, human chorionic gonadotrophin and alpha-fetoprotein as second trimester predictors of pre-eclampsia

Objective To compare the serum levels of human chorionic gonadotrophin (hCG), α-fetoprotein, activin A, inhibin A and inhibin isoforms containing pro and αC in the second trimester serum of women who subsequently developed hypertensive disorders of pregnancy with those who remained normotensive throughout pregnancy.
Design Retrospective case–control study of 15–20 week serum samples matched for duration of storage at −20°C.
Setting Antenatal clinics at a teaching hospital in Scotland.
Sample Second trimester serum samples of 39 women who subsequently developed pre-eclampsia, 31 who subsequently developed pregnancy-induced hypertension and 155 women who remained normotensive throughout pregnancy.
Main outcome measures hCG, α-fetoprotein, activin A, inhibin A and inhibin pro–αC serum levels.
Results Activin A levels in serum were significantly elevated in women who later developed pregnancy-induced hypertension (26% increase compared with controls) and hCG levels were significantly elevated in women who later developed pre-eclampsia (24% increase compared with controls). α-Fetoprotein, inhibin A and inhibin pro–αC levels were not significantly elevated in the patient groups compared with their controls.
Conclusions A combination of analyses including second trimester serum activin A and hCG may yet prove to be helpful predictors of women at risk of hypertensive disorders of pregnancy. While the results proved significant, the effects reported in this study are too modest compared with natural variability to be useful as screening tools on their own.     

Alteration in age-specific risks for chromosomal trisomy by maternal serum alpha-fetoprotein and human chorionic gonadotropin screening.

Maternal serum screening for alpha-fetoprotein (AFP) and human chorionic gonadotropin (hCG) increases the detection rate of Down's syndrome (DS) pregnancies. To estimate the risk of a DS pregnancy for a particular woman, Wald et al. combine a trivariate function of AFP, hCG, and unconjugated oestriol with age-specific risk. Calculation of independent likelihood ratios (LRs) for AFP and hCG has allowed us to examine the predictive value of each test alone and the combination. AFP and hCG were measured in stored serum samples from 672 normal, 8 trisomy 21 (DS), 9 trisomy 18, and 2 trisomy 13 pregnancies. AFP and hCG multiples of the median (MOM) were calculated for each sample. The LRs for AFP MOM and hCG MOM were calculated and combined with age-specific risk. Of eight DS pregnancies, six had increased risk based on age and AFP. Addition of hCG detected two additional DS pregnancies. Of nine trisomy 18 pregnancies, four (44 per cent) had hCG MOM under 0.25. Three out of nine would have been classified as high risk by AFP, but none by combined AFP and hCG. Amniocentesis would have been recommended in 74 per cent of aneuploid pregnancies if both age and serum screening were used. Abandonment of amniocentesis based on age alone would have excluded two abnormal pregnancies from detection. Screening programmes should note that combined risk figures are specific for DS and do not include other trisomies. Detection of other trisomies requires inclusion of low hCG level as a discriminator and continuation of age-based testing.     

The association between unexplained second-trimester maternal serum hCG elevation and pregnancy complications.

OBJECTIVE: We conducted this cohort analytic study to determine whether women with unexplained elevations of maternal serum hCG at 16-20 weeks' gestation are at increased risk for pregnancy complications and adverse perinatal outcomes. METHODS: The inclusion criteria were a singleton gestation, a confirmed gestational age, and an hCG level greater than 2.5 multiples of the median (MOM). The exclusion criteria were fetal anomalies, an abnormal karyotype, and a maternal serum alpha-fetoprotein (MSAFP) level greater than 2.5 MOM. A group of randomly selected women with normal hCG and MSAFP levels served as controls. RESULTS: Of the 6011 women screened, 284 (4.7%) had an unexplained elevated hCG level. Patients with elevated levels of hCG had a significantly higher risk for hypertension (odds ratio 4.4; 95% confidence interval [CI] 1.9-10) and fetal growth restriction (odds ratio 2.8; 95% CI 1-7). Women with hCG levels greater than 4 MOM also had an increased risk of preterm delivery (odds ratio 3.3; 95% CI 1.3-8.2). CONCLUSION: Pregnancies with unexplained elevated hCG levels should be regarded as high-risk pregnancies and managed accordingly.     

Prenatal screening for chromosome abnormalities using maternal serum chorionic gonadotrophin, alpha-fetoprotein, and age.

Human chorionic gonadotrophin (hCG) levels were assayed retrospectively in stored maternal serum samples from 78 chromosomally abnormal pregnancies and 410 controls matched for gestation and maternal age. The median serum hCG concentration in 49 pregnancies with Down's syndrome was significantly elevated, at 2.18 multiples of the normal median. Significantly reduced hCG concentrations were found in a group of four trisomy 18 pregnancies (all less than 0.4 multiples of the median). Eight cases of unbalanced chromosome rearrangements appeared to show some lowering of hCG levels, while there was no significant difference in the levels in the cases of trisomy 13, balanced translocations, and sex chromosome abnormalities. Maternal serum hCG alone is a better indicator of Down's syndrome pregnancies than maternal age or maternal serum alpha-fetoprotein (AFP), either individually or in combination, and provides a further virtually independent measure of risk. On the basis of our findings, screening for Down's syndrome using hCG and AFP results combined with maternal age risks is predicted to result in a higher detection rate (57 per cent) for a lower false-positive rate (5.0 per cent) than would be attainable by combined AFP and age screening (37 per cent detection at a 6.6 per cent false-positive rate).     

Screening for Down's syndrome: changes in marker levels and detection rates between first and second trimesters

Objective To monitor changes with gestation in levels of alpha-fetoprotein (AFP), free beta human chorionic gonadotrophin (FβhCG) and pregnancy associated plasma protein-A (PAPP-A) in Down's syndrome pregnancies and to compare risks estimated in the first trimester with those obtained by routine screening in the second trimester for the same pregnancies.
Design In each of 47 Down's syndrome pregnancies two maternal serum samples were obtained, one in the first trimester and one in the second trimester. Comparison of marker levels with 10,600 first trimester controls and a smaller sample of second trimester controls allowed case identification criteria based on optimum marker combinations to be developed and compared directly between trimesters.
Setting Biochemical genetics laboratory.
Results FβhCG was an effective marker of Down's syndrome in both the first and second trimesters. PAPP-A levels were significantly reduced in trisomy 21 pregnancies in the first trimester only. Using a population model, these two markers in combination with maternal age gave an overall detection rate of 55% for a 5% false positive rate in the first trimester. For the paired first and second trimester samples, three of six cases classified as low risk by routine second trimester screening were classified as high risk by the first trimester screening protocol of FβhCG/PAPP-A/matemal age. However, fifteen cases identified as high risk by routine second trimester screening were classified as low risk in the first trimester, a net loss in detection of 12 cases by first trimester screening.
Conclusion The data suggest that first trimester detection rates for Down's syndrome using a combination of FβhCG and PAPP-A may vary with gestation and will be lower than those currently obtained by routine second trimester screening with AFP/hCG.     

Serum markers for Down's syndrome in women who have had in vitro fertilisation: implications for antenatal screening

To examine the Down's syndrome screening positive rate among in vitro fertilisation (IVF) pregnancies, we measured second trimester serum marker levels in singleton IVF pregnancies (cases) and in five non–IVF pregnancies (controls) matched to each case for gestational age, age of mother, and duration of storage of the serum sample. There were 151 IVF pregnancies in which alpha fetoprotein, unconjugated oestriol (uE₃), free β–human chorionic gonadotrophin (hCG) and total hCG were measured, 104 IVF pregnancies in which free α-hCG was measured, and 39 IVF pregnancies in which inhibin A was measured. Median uE₃ levels were 6% lower (   P = 0.003  ), median free β–hCG 9% higher (   P = 0.024  ), and median total hCG 14% higher (   P = 0.026  ) in IVF pregnancies compared with controls. The screen positive rate in the IVF pregnancies (28%) was about twice as high as that in controls (17%). High hCG levels may be explained by progesterone remaining high in IVF pregnancies. The low uE₃ levels remain unexplained. In Down's syndrome screening in IVF pregnancies hCG and uE₃ values should be adjusted to avoid the high screen positive rate.     

First trimester maternal serum free beta human chorionic gonadotrophin and pregnancy associated plasma protein A as predictors of pregnancy complications

Objective To examine the value of first trimester maternal serum free β human chorionic gonadotrophin (β hCG) and pregnancy associated plasma protein A (PAPP-A) as predictors of pregnancy complications.
Design Screening study.
Setting Antenatal clinics.
Population Singleton pregnancies at 10–14 weeks of gestation.
Methods Maternal serum free β hCG and PAPP-A were measured at 10–14 weeks of gestation in 5584 singleton pregnancies. In the 5297 (94.9%) pregnancies with complete follow up free β hCG and PAPP-A were compared between those with normal outcome and those resulting in miscarriage, spontaneous preterm delivery, pregnancy induced hypertension or fetal growth restriction and in those with pre-existing or gestational diabetes.
Results Maternal serum PAPP-A increased and β hCG decreased with gestation. The multiple of median maternal serum PAPP-A was significantly lower in those pregnancies resulting in miscarriage, pregnancy induced hypertension, growth restriction and in those with pre-existing or gestational diabetes mellitus, but not in those complicated by spontaneous preterm delivery. The level was < 10th centile of the reference range in about 20% of the pregnancies that subsequently resulted in miscarriage or developed pregnancy induced hypertension or growth restriction, and in 27% of those that developed gestational diabetes. Maternal serum free β hCG was < 10th centile of the reference range in about 15% of the pregnancies that subsequently resulted in miscarriage or developed pregnancy induced hypertension or growth restriction, and in 20% of those that developed gestational diabetes.
Conclusion Low maternal serum PAPP-A or β hCG at 10–14 weeks of gestation are associated with subsequent development of pregnancy complications.     

Placental synthesis of oestriol in Down's syndrome pregnancies

In the second trimester, oestriol is synthesized in the placenta and secreted into the maternal circulation. 16alpha-hydroxy dehydroepiandrosterone sulphate (16alpha-OH-DHEAS) is formed in the fetal liver by hydroxylation of dehydroepiandrosterone sulphate (DHEAS) and transported to the placenta where it undergoes desulphation by steroid sulphatase (STS) and aromatization to oestriol. Maternal serum levels of unconjugated oestriol (UE3) are lower in Down's syndrome pregnancies than in unaffected pregnancies in the second trimester. The underlying cause of this variation was investigated in placenta, fetal liver, maternal serum and amniotic fluid from Down's syndrome pregnancies by measuring the levels of UE3, DHEAS and STS in appropriate tissues and in corresponding samples from unaffected pregnancies. UE3 levels, expressed as multiples of the control median at the appropriate gestation (MOM), were lower in placental tissue (0.52 MOM), maternal serum (0.65 MOM) and amniotic fluid (0.61 MOM) than in unaffected pregnancies. There was a significant correlation between placental and maternal serum levels of UE3 in the Down's syndrome cases. The median STS activity in placental tissue from Down's syndrome pregnancies (1.14 MOM) was not significantly different from that of the control pregnancies (1. 01 MOM), suggesting that placental turnover of the fetal precursor DHEAS is not reduced. However, levels of DHEAS were reduced in maternal serum (0.69 MOM), placental tissue (0.54 MOM) and fetal liver (0.65 MOM) from Down's syndrome pregnancies. Thus, a diminished supply of the fetal precursor DHEAS may be the cause of the decreased placental production of UE3 in Down's syndrome pregnancies in the second trimester.     

Unexplained elevated serum hCG is associated with raised amniotic fluid erythropoietin levels in second-trimester pregnancies.

OBJECTIVE: This study was designed to investigate the association between the concentrations of maternal serum hCG and amniotic fluid erythropoietin during the second trimester of pregnancy. METHODS: In a prospective case-control study, 42 consecutive singleton pregnancies showing unexplained elevated serum hCG concentrations (>2.0 multiples of the median, MoM) in Down's syndrome screening and 27 control pregnant women undergoing midtrimester amniocentesis because of a previous cytogenetic abnormality were studied. RESULTS: The mean amniotic fluid erythropoietin concentration in the study group was 1.8 (range 0.61-8.7) MoM, whereas it was 1.1 (range 0.71-3. 96) MoM in the controls (p = 0.035). A significantly increasing relationship (p < 0.05) was found between the concentrations of maternal serum hCG and amniotic fluid erythropoietin. CONCLUSIONS: The results of the current study revealed in vivo the association between elevated hCG and amniotic fluid erythropoietin levels which, in turn, supports the concept of early placental damage. The underlying pathology seems to be sufficient to cause an erythroblastic response.     

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

Objective To examine the fetal loss rate in women younger than 35 years of age following a false positive serum biochemical screening.
Design Retrospective analysis of case records between 1991 and 1998.
Setting Fetal medicine unit of a large teaching hospital.
Population Four hundred and fifty-six women with singleton pregnancies and false positive serum biochemical screening for Down's Syndrome (study group). Nine hundred and twelve matched controls with true negative serum biochemical screening (control group).
Methods Women of both groups had a second trimester serum screening for Down's Syndrome using alpha fetoprotein, human chorionic gonadotrophin (hCG) and unconjugated oestriol (uE₃); and they also underwent genetic amniocentesis.
Results The overall fetal loss rate in the study group was 5.3% (24/456), compared with 1.65% (15/912) in the control group RR 3.2, 95% CI 1.7-5.99;   P <0.001  ). The majority of fetal losses in the study group occurred after 28 weeks, while in the controls this happened between 24 and 28 weeks of gestation.
Conclusions A false positive serum biochemical screening in women under 35 years of age is associated with a threefold increased risk of subsequent fetal loss. However, most of fetal losses in this group occurred after 28 weeks, indicating that intensive antepartum fetal surveillance could improve the perinatal outcome.     

Variation in the levels of pregnancy-specific beta-1-glycoprotein in maternal serum from chromosomally abnormal pregnancies.

Human pregnancy-specific beta-1-glycoprotein (SP1) was assayed retrospectively in stored maternal serum (MS) samples from 82 chromosomally abnormal pregnancies and 377 matched controls. The median MSSP1 concentration in 48 Down's syndrome pregnancies was significantly elevated at 1.17 multiples of the control median (MOM), and significantly reduced (0.5 MOM) in a group of eight cases of unbalanced translocations. There was no significant difference in median SP1 concentrations in cases of trisomy 18, trisomy 13, balanced translocations, or sex chromosome abnormalities. A comparison with human chorionic gonadotrophin results in the same series of samples indicates that SP1 is a less sensitive predictor of Down's syndrome pregnancies.     

Detection of maternal serum hCG glycoform variants in the second trimester of pregnancies affected by Down syndrome using a lectin immunoassay

AIM: To assess whether glycoform variants of human chorionic gonadotrophin (hCG) are present in altered concentrations in the maternal serum in pregnancies affected by Down syndrome. METHODS: In a series of 50 cases of pregnancies complicated by Down syndrome and 278 unaffected pregnancies, we have examined maternal serum levels of hCG glycoforms (GlyhCG) in samples collected in the second trimester (14 to 21 weeks) using a sialic acid binding lectin immunoassay. We have compared these levels with those of other second trimester serum markers (Free beta-hCG, alpha fetaprotein (AFP) and Total hCG) and modelled detection rates and false positive rates of various biochemical markers in conjunction with maternal age using a maternal age standardized population. RESULTS: Maternal serum GlyhCG in cases of Down syndrome was significantly elevated (Median MoM 1.81) with 15 of 50 (30%) cases above the 95th centile for unaffected pregnancies. Free beta-hCG was also elevated (Median MoM 2.16) with 18 of 50 (36%) cases above the 95th centile. AFP levels were reduced (Median MoM 0.75) with 9 of 50 (18%) cases below the 5th centile. Total hCG levels whilst elevated (Median MoM 1.88) had only 15 of 50 (30%) cases above the 95th centile. Maternal serum GlyhCG levels showed significant correlation with total hCG and free beta-hCG (r = 0.6880 and 0.6922) in the Down group but not with AFP (r = 0.1237). When GlyhCG was combined together with AFP and maternal age, at a 5% false positive rate, the modelled detection rate was 53%, some 13% lower than when free beta-hCG was used and some 7% lower than when total hCG was used. CONCLUSION: Maternal serum GlyhCG, as measured by the sialic acid-binding lectin immunoassay is unlikely to be of additional value when screening for Down syndrome in the second trimester.     

Umbilical cord plasma homocysteine concentrations at delivery in pregnancies complicated by pre-eclampsia

Aim: To determine whether homocysteine concentrations in umbilical cord plasma of neonates born to mothers with pre-eclampsia are elevated compared to concentrations in neonates born to normotensive women.
Method: Maternal blood from eight women with pre-eclampsia and ten women without pre-eclampsia was collected on admission for labour. Cord blood was collected from these same pregnancies at delivery. Plasma was extracted and stored at −70°C. Samples were batch-analysed for homocysteine.
Result: Maternal plasma homocysteine levels were observed to be significantly higher in the pregnancies complicated by pre-eclampsia compared to the control pregnancies ( P  = 0.043) with median levels of 5.4 µmol/L (interquartile range (IQR) 4.6–7.9; range 3.6–16.7) versus 4.1 µmol/L (IQR 3.4–5.1, range 3.1–6.7). Homocysteine concentrations in umbilical cord plasma in pregnancies complicated by pre-eclampsia were also significantly higher compared to those in normotensive pregnancies ( P  = 0.016) with median concentration levels of 5.3 µmol/L (IQR 4.8–7.2, range 2.5–16.6) versus 3.8 µmol/L (IQR 2.8–4.4, range 0.8–1.6).
Conclusion: Both maternal and umbilical cord plasma homocysteine concentrations were elevated in pregnancies complicated by pre-eclampsia compared to normotensive controls.     

Clinical follow-up of high mid-trimester maternal serum intact human chorionic gonadotrophin concentrations in singleton pregnancies

Mid-trimester biochemical screening of 38 143 pregnancies in south-east Scotland revealed 127 cases (0.34 per cent) in which the maternal serum (MS) intact human chorionic gonadotrophin (hCG) concentration was > or = 4 multiples of the median in singleton pregnancies (MOM). Three were lost to follow-up but in 72 (58 per cent) complications developed or there were associated fetal abnormalities. This percentage was greatest at very high hCG concentrations, 92 per cent with hCG > or = 10 MOM (n = 12) compared with 48 per cent with hCG concentrations of 4-4.99 MOM (n=69). 22 cases had an MS alpha-fetoprotein > or = 2 MOM in addition to an MS hCG > or = 4 MOM, and in only 3 of these was the pregnancy uneventful; 86 per cent were associated with abnormalities or pregnancy complications.     

Intrahepatic cholestasis of pregnancy has no effect on maternal serum second trimester alpha-fetoprotein and hCG

OBJECTIVE: To investigate the association between intrahepatic cholestasis and Down's syndrome screening analytes (alpha-fetoprotein [AFP] and hCG) during the second trimester. DESIGN: Measurements of maternal serum AFP and hCG concentrations were retrospectively analyzed in relation to intrahepatic cholestasis in a cohort of 33 consecutive singleton pregnancies affected by cholestasis from January 1995 through December 1997 at the University Hospital of Kuopio, and then compared with those in healthy singleton control pregnancies (n=5680) from the same clinic over the same period of time. RESULTS: Geometric means of maternal serum AFP and hCG concentrations in pregnancies affected by cholestasis were 1.12 and 0.98 multiples of the median [MoM], respectively. Mean maternal age was significantly higher in the subjects than in controls (30.6 years compared with 28.8 years). In relation to Down's syndrome risk assessment, the pattern of the two markers together with maternal age indicated high risk as often in the study subjects as in the controls. CONCLUSION: Median serum AFP and hCG concentrations in pregnancies complicated by intrahepatic cholestasis were not significantly different from those in unaffected pregnancies. There is no need to take the hepatic disorder into account in maternal serum screening.     

First trimester screening for Down's syndrome using maternal serum PAPP-A and free β=hCG in combination with fetal nuchal translucency thickness

The aim of this study was to evaluate the potential effectiveness of maternal serum pregnancy-associated plasma protein A (PAPP-A) and free β-hCG in combination with nuchal translucency thickness in first trimester screening for Down's syndrome. Maternal serum levels of PAPP-A and free β-hCG were assayed in stored sera from 32 Down's syndrome and 200 unaffected pregnancies. Fetal nuchal translucency was measured by ultrasound at the time of blood sampling. Screening of Down's syndrome using a combination of maternal age, PAPP-A, free β-hCG and nuchal translucency would achieve a detection rate of 75.8% for a false positive rate of 5%.     

Effect of routine screening for Down's syndrome on the significance of isolated fetal hydronephrosis

Objective To determine the risk of Down's syndrome in fetuses with isolated hydronephrosis at 18–23 weeks in an unselected general population after routine screening for Down's syndrome, using first trimester nuchal translucency measurement and second trimester maternal serum biochemistry.
Population All pregnant women undergoing a routine 18–23 week ultrasound scan, from a population who had been offered screening for Down's syndrome.
Setting A district general hospital serving a low risk obstetric population.
Methods Prospective study of all routine 18–23 weeks ultrasound scans. The prevalence of isolated hydronephrosis and Down's syndrome was determined and the relative risk for Down's syndrome was calculated for different ultrasound findings.
Results 10,971 women were scanned at 18–23 weeks during the study period. Down's syndrome was diagnosed in 14 of 20 cases before this stage using first trimester nuchal translucency measurement and second trimester maternal serum biochemistry. Isolated fetal hydronephrosis was diagnosed in 423 pregnancies (3.9%); none of these pregnancies were affected by Down's syndrome. The relative risk for Down's syndrome was 0.18 (95% CI 0.06–0.53) for women with a normal scan (   n = 9983  ). When multiple ultrasound markers were found (   n = 565  ), the relative risk for Down's syndrome was 2.00 (95% CI 0.18–22-10) and 9.00 (95% CI 1.14–71.30) for all other aneuploidies.
Conclusion The finding of isolated fetal hydronephrosis does not significantly increase the age-related risk for Down's syndrome. The presence of multiple ultrasound markers is associated with an increased risk of aneuploidies other than Down's syndlome. These findings are explained by the reduced prevalence of Down's syndrome as a result of prior screening and diagnosis of this condition.     

Serum markers for Down's syndrome in women who have had in vitro fertilisation: implications for antenatal screening

To examine the Down's syndrome screening positive rate among in vitro fertilisation (IVF) pregnancies, we measured second trimester serum marker levels in singleton IVF pregnancies (cases) and in five non-IVF pregnancies (controls) matched to each case for gestational age, age of mother, and duration of storage of the serum sample. There were 151 IVF pregnancies in which alpha fetoprotein, unconjugated oestriol (uE3), free beta-human chorionic gonadotrophin (hCG) and total hCG were measured, 104 IVF pregnancies in which free alpha-hCG was measured, and 39 IVF pregnancies in which inhibin A was measured. Median uE3 levels were 6% lower (P = 0.003), median free beta-hCG 9% higher (P = 0.024), and median total hCG 14% higher (P = 0.026) in IVF pregnancies compared with controls. The screen positive rate in the IVF pregnancies (28%) was about twice as high as that in controls (17%). High hCG levels may be explained by progesterone remaining high in IVF pregnancies. The low uE3 levels remain unexplained. In Down's syndrome screening in IVF pregnancies hCG and uE3 values should be adjusted to avoid the high screen positive rate.