Significance of elevated mid-trimester maternal plasma-alpha-fetoprotein values

Cytomegalovirus infection in association with early onset pre-eclampsia

This case describes a woman who presented with raised α-fetoprotein (AFP) on second trimester screening, and developed early onset fetal growth restriction (FGR) and severe pre-eclampsia (PET) before 24 weeks' gestation requiring magnesium sulphate and intravenous antihypertensives. Ultrasonography revealed a structurally normal fetus with estimated weight <3rd centile, abnormal uterine artery Dopplers and deteriorating fetal arterial Dopplers over the following 2 weeks. The pregnancy ended in fetal death before a viable weight was reached. Postmortem examination revealed a growth restricted fetus (birth weight <0.4th centile) and chronic villitis secondary to placental cytomegalovirus (CMV) infection. CMV has previously been associated with PET and FGR. This case highlights its potential role in the pathogenesis of placental failure and has relevance for counselling and management for future pregnancies. Furthermore, raised AFP may represent ongoing placental damage and offers potential for future therapeutic measures--for example, antivirals or immunisations to alter the natural history and prognosis of placental infection.

Early second trimester (13 to 20 weeks) transabdominal chorionic villus sampling (TA-CVS): a safe and alternative method for both high and low risk populations

OBJECTIVE

To assess feasibility, effectiveness and risk of prenatal diagnosis by TA-CVS at 13-14 and 15-20 weeks' gestation.

METHODS

CVS was performed transabdominally by free-hand single needle insertion technique under continuous ultrasound visualization on 1844 pregnant women, aged 18 to 48, at 13 to 20 weeks' gestation, whose primary indication was chromosomal anomalies and single gene defects in 85% and 15% of cases, respectively Clinical follow-up of women undergoing TA-CVS at 13 to 20 weeks' was prospectively obtained; the population was split in two groups of 13-14 (series B) and 15-20 weeks' (series C) gestation. Statistical evaluation included a group of TA-CVS cases performed at 11-12 weeks (series A).

RESULTS

Sampling was feasible in 98.2%, 99.1% and 95.8% of cases of series A, B and C, respectively. Sampling was successful in all cases of the three series and a second insertion was required in 1.5%, 1.3% and 0.9%, respectively. A trend towards lower fetal loss rate is apparent (1.02%, 0.86%, and 0.46 in series A, B, and C, respectively), although differences were not statistically significant. No post-procedural complications were reported for series B and C, while spotting was present in 1.8% of cases for series A. Karyotyping was totally successful by short term culture and was also available by long term culture in 99% of cases for series A, B and C when the amount of chorionic tissue was more than 15 mg.

CONCLUSION

TA-CVS appears highly effective and safe and might be offered as a valuable alternative to early as well as mid-trimester amniocentesis.

Associations between adverse perinatal outcome and serially obtained second- and third-trimester maternal serum alpha-fetoprotein measurements

OBJECTIVE

Our purpose was to determine whether third-trimester maternal serum alpha-fetoprotein predicts adverse perinatal outcome and whether use of both second- and third-trimester maternal serum alpha-fetoprotein enhances the positive predictive value for various abnormal outcomes.

STUDY DESIGN

A cohort study with obstetric outcome assessed by chart analysis after delivery was performed at Regional Medical Center (Memphis, Tennessee), a hospital staffed by university-based physicians serving a large urban population with many indigent patients. A total of 650 women attending prenatal clinics in the above setting with a singleton pregnancy without a neural tube defect, contributing a maternal blood samples in both the second and third trimesters, and delivered in the above hospital participated. Various pregnancy outcomes were correlated with maternal serum alpha-fetoprotein levels in the second and third trimesters and in both.

RESULTS

In the third trimester no significant associations were found between maternal serum alpha-fetoprotein elevations and pregnancy complications. In the second trimester elevation ( > or = 2.0 multiples of the median) were, by contrast, significantly associated with preterm premature rupture of the membranes, preterm birth, and low birth weight. No association was found with certain other complications. When second-trimester data were grouped according to the types of complications occurring in individual women, only preterm premature rupture of the membrane proved statistically significant.

CONCLUSIONS

Second-trimester but not third-trimester maternal serum alpha-fetoprotein is significantly elevated with preterm premature rupture of the membranes, preterm birth, and low birth weight; in this cohort study no association was found with preeclampsia, oligohydramnios, or polyhydramnios.

Abnormal levels of maternal serum human chorionic gonadotropin and alpha-fetoprotein in the second trimester: relation to fetal weight and preterm delivery

The aim of this prospective descriptive cross-sectional study was to examine the clinical significance of abnormal maternal serum human chorionic gonadotropin (MShCG) and alpha-fetoprotein (MSAFP) in the second trimester of pregnancy. The study group comprised 8892 women with a singleton pregnancy, who were screened for a neural tube defect and Down's syndrome. Exclusion criteria were unknown pregnancy outcome, a congenital anomaly, delivery before 25 weeks of amenorrhoea, or known insulin-dependent diabetes. MSAFP and MShCG were determined between 15 and 20 weeks' amenorrhoea. An abnormal result was defined as (a) MSAFP or MShCG > or = 2.5 MOM, (b) MSAFP or MShCG < or = 0.5 MOM, and (c) MSAFP and MShCG > or = 2.5 MOM. Birth weight percentiles and the duration of amenorrhoea at the time of delivery were employed as outcome parameters. Of the women with an abnormally elevated MSAFP, 9.4 per cent had an extremely small-for-gestational age (SGA) infant (< 2.3rd percentile; P < 0.01, relative risk 4.5), 27.1 per cent had an SGA infant (< tenth percentile; P < 0.01, relative risk 2.7), and 14.3 per cent had an appropriate-for-gestational age (AGA) infant that was delivered preterm (< 259 days; P < 0.01, relative risk 2.4). In the cases where the MShCG level was elevated, 4.4 per cent had an extremely SGA infant (P < 0.01, relative risk 2.1) and 15.5 per cent had an SGA infant (P < 0.01, relative risk 1.5). No significant association was found between an elevated MShCG level and preterm delivery. Low MShCG was significantly associated with SGA infants (P < 0.01, relative risk 1.2) but not with extremely SGA or preterm deliveries. In the group whose MSAFP and MShCG levels were both elevated, 23.8 per cent delivered an extremely SGA infant (P < 0.01, relative risk 10.9), 38.1 per cent an SGA infant (P < 0.01, relative risk 3.7) and 47.6 per cent had a preterm delivery or an SGA infant (P < 0.01, relative risk 3.0). Isolated or combined elevation of the MSAFP and MShCG levels in the second trimester of pregnancy is an indication for extra vigilance during further prenatal care. This applies to a lesser extent to a low MShCG level.

Unexplained elevated maternal serum alpha-fetoprotein levels and perinatal outcome in an urban clinic population

OBJECTIVE

Our purpose was to determine whether obstetric patients with unexplained elevated maternal serum alpha-fetoprotein levels from an indigent clinic population are at increased risk for adverse perinatal outcome compared with similar patients with normal values.

STUDY DESIGN

Perinatal outcomes from inner-city obstetric patients with unexplained elevated maternal serum alpha-fetoprotein levels (> 2.0 multiples of the median) were compared with patients from the same clinic with normal values. The frequency of adverse outcomes in the two groups was subjected to chi 2 analysis.

RESULTS

Adverse perinatal outcomes occurred in 33 of 57 (58%) of the subjects with unexplained elevated maternal serum alpha-fetoprotein levels compared with 163 of 719 (23%) patients with normal values (p < 0.001). Statistically significant differences were observed for abruptio placentae (p < 0.025), intrauterine growth retardation (p < 0.025), stillbirth at > 20 weeks (p < 0.001), and pregnancy-induced hypertension (p < 0.01). Differences in the frequencies of preterm premature rupture of membranes, preterm delivery, pregnancy loss < 20 weeks, and congenital malformations were not statistically significant.

CONCLUSION

In contrast to a previous report, we found that unexplained elevated maternal serum alpha-fetoprotein levels confer an increased risk of adverse perinatal outcome in an urban clinic population over and above the already increased risk related to socioeconomic status.

Circulating intercellular adhesion molecule-1 in amniotic fluid, maternal serum alpha-fetoprotein levels, and intrauterine growth retardation

OBJECTIVE

Our purpose was to determine if circulating intercellular adhesion molecule-1, a marker of chronic inflammation, is present in amniotic fluid in midtrimester, is increased in patients with elevated maternal serum alpha-fetoprotein level, and is associated with intrauterine growth retardation.

STUDY DESIGN

Amniotic fluid circulating intercellular adhesion molecule-1 levels were assayed by enzyme-linked immunoassay in 273 samples obtained by midtrimester amniocentesis in gestations involving a single, structurally normal fetus. The control group consisted of 108 patients with normal maternal serum alpha-fetoprotein levels and 165 patients with elevated levels. Intrauterine growth retardation was diagnosed if birth weight was < 10th percentile for the clinically estimated gestational age.

RESULTS

Circulating intercellular adhesion molecule-1 was detectable in amniotic fluid in 105 of 273 samples (38%). In the control group it was detectable in amniotic fluid in seven of 108 (6%). In patients with elevated maternal serum alpha-fetoprotein 97 of 164 (59%) had detectable levels (p < 0.001). Of the 273 cases 38 (14%) had intrauterine growth retardation. Of these 23 (59%) had detectable circulating intercellular adhesion molecule-1 levels (p < 0.001). Of the seven cases of intrauterine growth retardation with normal maternal serum alpha-fetoprotein levels, one (14%) had detectable circulating intercellular adhesion molecule-1. Of the 31 cases of intrauterine growth retardation with elevated maternal serum alpha-fetoprotein 22 (71%) had detectable circulating intercellular adhesion molecule-1. When circulating intercellular adhesion molecule-1 was detectable in amniotic fluid, increasing levels was significantly related to decreasing gestational age at delivery (p < 0.005).

CONCLUSIONS

Midtrimester amniotic fluid from normal pregnancies does not generally contain detectable circulating intercellular adhesion molecule-1. Detectable amniotic fluid levels are significantly related to a birth weight < 10th percentile at delivery and to elevated midtrimester maternal serum alpha-fetoprotein levels. Increasing circulating intercellular adhesion molecule-1 levels are related to shortened length of gestation. This test may contribute to risk assessment for intrauterine growth retardation and prematurity. Circulating intercellular adhesion molecule-1 is a known marker of inflammatory processes; its further study may also improve understanding of the pathophysiologic mechanisms of certain cases of intrauterine growth retardation and prematurity.

Elevated levels of midtrimester maternal serum alpha-fetoprotein are associated with preterm delivery but not with fetal growth retardation

OBJECTIVE

Our objective was to determine if the low birth weight associated with unexplained elevations of midtrimester maternal serum alpha-fetoprotein levels is due to prematurity or to fetal growth retardation.

STUDY DESIGN

Rates of preterm delivery and fetal growth retardation were analyzed according to incremental maternal serum alpha-fetoprotein levels in 5555 women, predominantly white, who were screened for neural tube defects (group 1) and 843 women, predominantly black, with risk factors for low birth weight (group 2). Statistical methods included chi 2, t tests, analysis of variance, and regression analysis.

RESULTS

In both groups increasing levels of maternal serum alpha-fetoprotein are significantly associated with preterm delivery but not with fetal growth retardation. The preterm delivery rate increased in each group from 8% at levels less than 0.5 multiples of the median to 18.1% (p less than 0.001) at levels greater than or equal to 2.5 multiples of the median in group 1 and 28.1% (p = 0.01) in group 2.

CONCLUSIONS

Women with unexplained elevations of maternal serum alpha-fetoprotein are at increased risk for preterm delivery but not fetal growth retardation. Because of the wide availability of maternal serum alpha-fetoprotein screening, women at increased risk for preterm delivery can be identified in the midtrimester of pregnancy.

Increased maternal serum alpha-fetoprotein and human chorionic gonadotropin in compromised pregnancies other than for neural tube defects or Down syndrome

Intrauterine fetal death occurred in four women who were 'screen-positive' in a screening programme for neural tube defects (NTDs) and Down syndrome (DS). These women had very high levels of maternal serum alpha-fetoprotein (MSAFP) and maternal serum human chorionic gonadotropin (MShCG). Therefore, we evaluated all 'screen-positive' women in whom both of these markers were greater than or equal to 2.0 multiples of the median. The cases fulfilling these criteria totalled 11, and only one of them had no complications. High concentrations of both MSAFP and MShCG in a number of these cases might have been caused by an increased placental volume, which, in turn, might have been induced by decreased perfusion of the placenta. We conclude that screening programmes wrongly determine a high risk of fetal NTD or DS if the concentrations of both these parameters are very high. Invasive diagnostic procedures should be avoided in these cases, particularly in view of the increased risk of an adverse pregnancy outcome.

Unexplained elevated maternal serum α-fetoprotein is not predictive of adverse perinatal outcome in an indigent urban population

OBJECTIVE

The null hypothesis of this study is that in an urban, indigent obstetric population at high risk for adverse perinatal outcome, unexplained elevations of maternal serum alpha-fetoprotein are not an additional predictor of adverse perinatal outcome.

STUDY DESIGN

Perinatal outcomes of 72 patients from a clinic for indigent patients with unexplained elevated maternal serum alpha-fetoprotein levels were compared with those of matched controls from the same population with normal maternal serum alpha-fetoprotein levels. Subjects and controls were matched for age, race, parity, and presence or absence of Hollister risk factors. The frequency of adverse perinatal outcome in the two groups was subjected to matched-pair chi 2 analysis.

RESULTS

Adverse perinatal outcome occurred in 38.9% (28 of 72) of subjects with unexplained elevated maternal serum alpha-fetoprotein levels greater than or equal to 2.5 multiples of the median, compared with 31.9% (23 of 72) of controls with normal maternal serum alpha-fetoprotein levels (p = 0.5). No statistically significant difference in adverse perinatal outcomes was found.

CONCLUSIONS

Elevated maternal serum alpha-fetoprotein levels offer little if any additional predictive value for adverse perinatal outcome in populations already at high risk for such outcomes on the basis of obstetric or socioeconomic criteria.

Second-trimester maternal serum alpha-fetoprotein levels and the risk of subsequent fetal death

BACKGROUND

The finding of an elevated level of maternal serum alpha-fetoprotein during the second trimester of pregnancy may indicate that the fetus has died or is about to die. It is uncertain, however, whether the finding is associated with an increased risk of fetal death later in gestation independent of known causes of elevation, such as the presence of neural-tube defects or multiple gestation.

METHODS

To address this question, we performed a case-control study of 612 women whose pregnancies ended in fetal death and 2501 women who gave birth to live infants, using reports from California vital statistics for 1987. All the women had signleton pregnancies and alpha-fetoprotein screening in the second trimester.

RESULTS

Women with elevated levels of serum alpha-fetoprotein in the second trimester of pregnancy had an increased risk of fetal death, and the risk was increased until term. Women with the highest levels of serum alpha-fetoprotein--greater than or equal to 3.0 times the median value--had a very high risk of fetal death (odds ratio, 10.4; 95 percent confidence interval, 4.9 to 22.0) as compared with women who had normal levels of alpha-fetoprotein. Maternal serum alpha-fetoprotein levels that were 2.0 to 2.9 times the median were also associated with an elevated risk of fetal death (odds ratio, 2.4; 95 percent confidence interval, 1.7 to 3.4). Elevated levels of alpha-fetoprotein were especially likely to be associated with fetal death in cases in which maternal hypertension or placental infarction was also present. CONCLUSIONs. An unexplained elevated level of maternal serum alpha-fetoprotein in the second trimester of pregnancy is associated with an increased risk of subsequent fetal death, up to four to five months after alpha-fetoprotein screening.

Does unexplained second-trimester (15 to 20 weeks' gestation) maternal serum alpha-fetoprotein elevation presage adverse perinatal outcome? Pitfalls and preliminary studies with late second- and third-trimester maternal serum alpha-fetoprotein

Several reports have suggested that persons with an unexplained maternal serum alpha-fetoprotein elevation at 15 to 20 weeks' gestation are at an increased risk for a variety of other pregnancy complications (e.g., preeclampsia) and adverse perinatal outcomes (e.g., fetal death, low-birth-weight infants). However, ascertainment biases could explain some of these reported findings, and predictive value of unexplained elevated maternal serum alpha-fetoprotein levels in the prediction of pregnancy complications seems limited. If elevated second-trimester levels were truly predictive of pregnancy complications, we reason that third-trimester levels could prove even more useful. We thus studied late second-trimester and early third-trimester (24 to 36 weeks' gestation) maternal serum alpha-fetoprotein levels with the same enzyme immunoassay we use to evaluate routine second-trimester (15 to 20 weeks' gestation) levels. Values rose up to 32 weeks and fell slightly thereafter. Variance was greater than at 15 to 20 weeks but not so great as to preclude clinical usefulness in the third trimester. Of 279 women with a normal (0.4 to 2.49 multiples of the median) maternal serum alpha-fetoprotein value at 15 to 20 weeks' gestation, 270 (96.8%) showed levels in the same range later in gestation; however, none of six singleton pregnancies with unexplained maternal serum alpha-fetoprotein levels greater than 2.50 multiples of the median at 15 to 20 weeks' gestation showed maternal serum alpha-fetoprotein levels in this range at 24 to 36 weeks' gestation. The relationship between second- and third-trimester maternal serum alpha-fetoprotein levels in abnormal pregnancies remains to be elucidated in a large sample. Thus we are conducting not only cohort but also cross-sectional studies. Preliminary findings suggest that women with preterm premature rupture of membranes or with premature labor show elevated late second-trimester and early third-trimester maternal serum alpha-fetoprotein levels; however, larger sample sizes are necessary.

Maternal serum alpha-fetoprotein levels in pregnancies among black and white women with fetal open spina bifida: a United States collaborative study

In the present study second-trimester maternal serum alpha-fetoprotein levels were analyzed from 146 pregnancies associated with fetal open spina bifida to identify whether affected pregnancies from the black population were associated with higher maternal serum alpha-fetoprotein levels than their white counterparts. Pregnancies in black women not affected by open spina bifida are already known to have higher maternal serum alpha-fetoprotein levels. All of the cases were analyzed with gestational ages assigned by last menstrual period, and all maternal serum alpha-fetoprotein values were expressed as multiples of the median, to correct for differences in gestational age and assay among the 15 centers reporting data. The levels from affected pregnancies in white and black women fit log Gaussian distributions, with medians of 3.10 and 4.37 multiples of the median, respectively, on the basis of singleton, unaffected, white pregnancy medians. These results support adjustment of maternal serum alpha-fetoprotein values for race in black women; in addition, if a screening program's policy is to screen at a comparable risk in the two races, a higher maternal serum alpha-fetoprotein multiple of the median cutoff would be justified for black women.

Neonatal progeroid syndrome: more than one disease?

We report on an infant with the neonatal progeroid syndrome whose clinical course and autopsy findings indicate that this may be a heterogeneous phenotype. The infant had intrauterine growth retardation, absence of subcutaneous fat, and a wizened, aged face, all apparently characteristic of the condition, but also had congenital heart defects and urinary reflux not reported in previous cases. An elevated maternal serum alpha fetoprotein was noted at 16 weeks of gestation and late-onset growth retardation appeared after 31 weeks. Autopsy findings showed normal cerebral myelination, in contrast to findings of sudanophilic leukodystrophy in the one patient with the syndrome previously examined at autopsy. These findings suggest that the neonatal progeroid syndrome may be a phenotype and have more than one cause.

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

Placental alkaline phosphatase (P-ALP) was measured by a specific monoclonal antibody-based immunoassay in plasma samples of 117 women who subsequently were delivered of an infant of birthweight less than 2.5 kg. P-ALP values greater than twice the normal median were found in 32% of maternal plasma samples from low birthweight cases in one series and in 35% in another series, while in normal outcome controls the corresponding value was 8%. The differences were highly significant. The proportion of low birthweight cases with elevated maternal P-ALP values appears to be very similar between 15 and 34 weeks gestation. At 16-18 weeks gestation there is a significant positive correlation (r = 0.40) between P-ALP and maternal plasma alpha-fetoprotein (AFP) values in low birthweight cases. The use of P-ALP assay in combination with AFP assay appears to improve the detection of pregnancies with subsequent low birthweight outcome.

Randomised controlled trial of genetic amniocentesis in 4606 low-risk women

Outcome of pregnancy after amniocentesis was studied in a randomised controlled trial of 4606 women, age-range 25-34 years, without known risk of genetic disease. Spontaneous abortion rate was 1.7% in the study group after amniocentesis and 0.7% in the control group after ultrasound (relative risk 2.3). In the study group, increased levels of maternal serum alpha-fetoprotein before amniocentesis, perforation of the placenta during amniocentesis, and withdrawal of discoloured amniotic fluid were associated with an increased risk of spontaneous abortion. In the first six weeks after amniocentesis/ultrasound scan, amniotic fluid leakage occurred more often in the study group but there was no difference in the rate of vaginal bleeding. Frequency of postural malformations in the infants in the two groups was the same. In the study group, respiratory distress syndrome was diagnosed more often (relative risk 2.1) and more babies were treated for pneumonia (relative risk 2.5).

Alpha-fetoprotein, vaginal bleeding and pregnancy risk

To assess the interrelation between maternal serum alpha-fetoprotein (MSAFP) levels and vaginal bleeding as a combined pregnancy risk factor, we studied 6829 singleton pregnancies without fetal malformations during the second trimester. The predictive powers of the two risk factors, analysed separately, are consistent with published reports in relation to fetal death and low birthweight. Until now, however, these two risk factors have not been analysed together. The present study demonstrates that MSAFP and vaginal bleeding are largely independent of each other as predictors of fetal death, relative risks being 0.7 (MSAFP less than 0.7 multiples of the median (MoM), vaginal bleeding absent), 3.5 (MSAFP less than 2.0 MoM vaginal bleeding present), 5.8 (MSAFP greater than or equal to 2.0 MoM, vaginal bleeding absent), and 12.6 (MSAFP greater than or equal to 2.0 MoM, vaginal bleeding present). Corresponding risks for low birthweight are: 0.7, 1.8, 2.5 and 1.6 (mean birthweights in the four categories are 3516 g, 3407 g, 3238 g, and 3176 g).

Justification of maternal serum alphafetoprotein screening in a population with low incidence of neural tube defects

A prospective study of maternal serum alphafetoprotein (alpha-FP) screening of 9838 women in an area with low prevalence of neural tube defects and predominance of anencephalics revealed that an intervention point of single serum alpha-FP level above 2.8 times the median was appropriate for this population. Ninety per cent of anencephalics and all fetuses with anterior abdominal wall defects were detected. There was no spina bifida among the population screened. Two per cent of the population screened had serum alpha-FP level above this cut-off level. Thirty-two per cent of twin pregnancies, 7 per cent of small-for-gestational age infants and 9 per cent of pregnancies which ended in either abortion or perinatal death in the population screened also had one serum alpha-FP level above this intervention point. The false positive rate was 66 per cent. This false positive rate was only reduced to 63 per cent if instead of one, two serum alpha-FP level above this intervention point was considered abnormal. Using this strategy there was no significant reduction in the detection rate of fetal anomalies and other pregnancy complications. Because of the predominance of anencephalics in this population the diagnosis of fetal anomaly in women with abnormal serum alpha-FP level was made by ultrasound examination alone. The reason amniocentesis was not performed in these patients was to avoid unnecessary loss of normal pregnancies which may result from this procedure.

Mid-trimester levels of alphafetoprotein in the screening of low birthweight

Elevated maternal levels of alphafetoprotein (AFP) in midtrimester are believed by some to be a useful screening test for premature labour, low birthweight and low birthweight for gestation. In a prospective study on 887 randomly selected pregnant women we found that although there was an association between low birthweight and elevated AFP, the test would miss five out of every six cases of low birthweight and there would be nine false-positives for every case correctly identified. The test is not therefore sufficiently predictive of low birthweight to be of value as a screening test for this condition.

Second trimester maternal serum alpha-fetoprotein as an indicator of fetal risk

Serum alpha-fetoprotein levels were raised to 2.0 or more times the median for gestation in 30 of 507 singleton pregnancies after excluding pregnancies complicated by fetal neural tube defects. The serum alpha-fetoprotein levels were significantly more often elevated in pregnancies complicated by prematurity, fetal heart rate abnormalities, delivery of a small for dates infant, a perinatal death and admission of the baby to the neonatal unit. While the predictive value of an elevated serum alpha-fetoprotein was 76% for abnormal outcomes in general it ranged between only 16% and 46% for specific abnormalities. The usefulness of this assay relates only to its ability to predict an abnormal outcome when performed during the second trimester.

Maternal serum alpha-fetoprotein in twin pregnancies uncomplicated by neural tube defect

The maternal serum alpha-fetoprotein concentration was measured between 16 and 20 weeks in 145 twin pregnancies in which neither fetus had a neural tube defect. When the maternal serum alpha-fetoprotein concentration was less than two multiples of the singleton median, pregnancy outcome was good; the extended perinatal mortality rate was 32.6/1000, mean birth weights for the first and second twins were 2507 and 2443 gm, respectively, and mean gestation at delivery was 36 weeks, 6 days. When the maternal serum alpha-fetoprotein concentration was greater than four multiples of the singleton median, the outcome was poor; the extended perinatal mortality was 400/1000, mean birth weights were 1963 and 1523 gm, and mean gestation at delivery was 32 weeks, 4 days. The negative correlations of maternal serum alpha-fetoprotein concentration with birth weight and gestation at delivery were highly significant. Maternal serum alpha-fetoprotein concentration in midpregnancy is a useful predictor of outcome in twin pregnancy, independent of the occurrence of neural tube defect, and it appears to be related to the timing of delivery rather than fetal growth.

alpha-Fetoprotein: relationship between maternal serum and amniotic fluid levels

Levels of alpha-fetoprotein were determined in 297 paired samples of maternal serum and amniotic fluid from patients with normal pregnancies at 16 to 17 completed weeks of gestation. Gestational ages were determined by menstrual history and ultrasonography, and the assays for alpha-fetoprotein were performed by a single reference laboratory. The results of the study failed to demonstrate any statistical relationship between the concentrations of alpha-fetoprotein in these two fluid compartments (r = 0.006). This finding was confirmed when the results at 16 and 17 weeks were analyzed individually. These findings indicate that amniotic fluid levels of alpha-fetoprotein cannot be predicted by those levels determined in maternal serum, and that simple diffusion is an inadequate explanation for the transfer of alpha-fetoprotein from amniotic fluid to maternal serum. The lack of correlation also emphasizes that the sensitivity and specificity of maternal serum alpha-fetoprotein screening for neural tube defects must continue to be based upon the detection rates in large population studies and the determination of "normal" values by reference laboratories.

Renal pathology of prenatally diagnosed nephrosis

Congenital Finnish nephrosis is a rare autosomal-recessive disorder, usually fatal at an early age. The disease is prenatally detected through elevation of alpha fetoprotein in the amniotic fluid of pregnancies at risk. This originates from fetal proteinuria. Maternal serum alpha fetoprotein reflects amniotic fluid levels. We describe a case of congenital nephrosis diagnosed through maternal serum screening in a low-risk population. The characteristic histology of congenital nephrosis is demonstrated, and evidence of proteinuria by electron microscopy, light microscopy, and immunofluorescence is presented.

Maternal serum alpha-fetoprotein screening for neural tube defects. Report of a combined study in Germany and short overview on screening in populations with low birth prevalence of neural tube defects

The basis of maternal serum alpha-fetoprotein (AFP)-screening for neural tube defects is discussed. A report is given of a large scale screening study in the Federal Republic of Germany combining the experiences in Giessen and Hannover on over 50,000 pregnant women, about evenly distributed among both centers. Published and known forthcoming data from other low incidence populations, particularly of European countries, are reviewed briefly. The conclusion is reached that general screening could effectively be instituted and in the final result should also be cost-beneficial.

Clinical interpretation of maternal serum alpha-fetoprotein concentrations

Concentrations of maternal serum alpha-fetoprotein provide the basis for decisions to proceed to ultrasonography and amniocentesis in the multistaged screening/diagnostic process used for the prenatal detection of open neural tube defects, abdominal wall defects, and twins. The concentration of maternal serum alpha-fetoprotein at or above which women should be advised that amniocentesis is available (cutoff levels for amniocentesis) varies, depending upon a number of factors, such as maternal weight, race, residence, and gestational age. We briefly describe a methodology for computing the predicted risks of fetal conditions associated with a given concentration of maternal serum alpha-fetoprotein adjusted for important variables. This adjustment methodology provides a straightforward means for clinical laboratories to report results of assays of maternal serum alpha-fetoprotein in terms of predicted risks, to facilitate understanding by the physician and patient of the clinical meaning of the results of maternal serum alpha-fetoprotein testing.

A cost-benefit analysis of a population screening programme for neural tube defects

Population screening for neural tube defects is possible by measuring maternal serum alphafetoprotein levels with appropriate follow-up as required. British Columbia has approximately 39 000 births annually and the incidence of neural tube defects is 1.55 per 1000 births (0.94 per 1000 livebirths). Results from a cost-benefit analysis suggest that the outlined screening programme would be cost-beneficial for British Columbia. Other important factors essential to consider before instituting a population screening programme are discussed.

Second-trimester placental changes associated with elevated maternal serum alpha-fetoprotein

Measuring maternal serum alpha-fetoprotein (AFP) levels in the second trimester is an effective screening test for identifying pregnancies at increased risk for neural tube defects. In the absence of a neural tube defect there are many nonpathologic and pathologic causes for elevated AFP including underestimated gestational age, twin gestation, impending fetal death, and rare fetal malformations. In this series, intraplacental sonolucent spaces were detected in a significant percentage of second trimester pregnancies with elevated serum AFP in the absence of any other cause for the elevation. It is postulated that these cystic spaces are a conduit for the transfer of fetal blood into the maternal circulation, thus accounting for the nonpathologic AFP elevation in the maternal serum.

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

Maternal serum alpha-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 less than 2.5 MOM, 7.8% had levels greater than 5 MOM and 59% of these were associated with either abortion, stillbirth or fetus papyraceous. In twin pregnancies with serum AFP levels less than 5 MOM and unsuccessful outcome was noted in only 4% (chi 2, P less than 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 greater than 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.

Impact of maternal serum alpha-fetoprotein screening on antenatal diagnosis

An analysis has been made of indications for amniocentesis in the Edinburgh area from 1979 to 1981. About 5% of all mothers underwent the procedure. Among 2137 amniocenteses, 37% were performed on mothers 35 years old or more, and 30% on patients with raised serum alpha-fetoprotein. The total number of amniocenteses and the categories have been stable for the past three years. As a result of amniocentesis 104 pregnancies were terminated, 66 of which (63%) followed a raised maternal serum alpha-fetoprotein indication, while only 10 (9.6%) were in mothers aged 35 or more. There were a further 12 terminations based on raised serum alpha-fetoprotein but where no amniocentesis had been thought necessary. Even when figures for anencephaly are excluded from the analysis, maternal serum alpha-fetoprotein screening was responsible for detecting 35 out of 63 (56%) abnormal fetuses. This constitutes a strong case for the continuation of alpha-fetoprotein screening programmes.

Maternal plasma alpha-fetoprotein and low birthweight: a prospective study throughout pregnancy

Maternal plasma alpha-fetoprotein (AFP) was measured serially between 15 weeks gestation and term in 520 patients. Thirty-seven of these women were delivered of normal singleton infants with birthweights less than 2.5 kg. The median plasma AFP values in this group of women were highest between 15 and 20 weeks gestation and then declined steadily towards term. It is concluded that the use of maternal plasma or serum AFP in the early detection of low birthweight babies is optimal in the period most suitable for screening for fetal neural tube defects.

Four years' experience of maternal alpha-fetoprotein screening and its effect on the pattern of antenatal care

Estimation of alpha-fetoprotein (A.F.P.) in maternal serum was used as a screening method for the detection of fetal neural tube defect (N.T.D.) in 7315 women over a four year period. Of these, 5668 pregnancies were tested between 15 and 21 weeks. Action was advised in 129 patients (2.3 per cent). In 74 patients, the only action required was reviewing the notes, including the report of any ultrasound examination, and repeating the blood A.F.P. Detailed ultrasound including scanning the fetal spine was requested in 47 patients and amniocentesis was advised in 19 of these (0.33 per cent). In practice the incidence of amniocentesis was 0.28 per cent as three patients declined our advise. The programme gave detection rates between 15 and 21 weeks of 100 per cent and 75 per cent respectively for anencephaly and open spina bifida. A high fetal mortality was associated with persistently elevated blood A.F.P. levels whether amniocentesis was performed or not.

Raised maternal serum AFP, oligohydramnios and poor fetal outcome

Six women who had an ultrasound scan examination in early pregnancy on account of a high serum alpha-fetoprotein level were noted to have little or no amniotic fluid. This paper gives details of the six pregnancies, two of which were extrauterine; only one of the six infants survived.

Prenatal fetal karyotyping and maternal serum alpha-fetoprotein screening

Prenatal karyotyping was undertaken in 569 consecutive amniotic fluid samples where the indication for amniocentesis was two sequential raised maternal serum alpha-fetoprotein concentrations. In 475 successful cultures five chromosome abnormalities were found--four constitutional anomalies (47,XXY; 47,XYY; an inherited inv(8) (p23q11); and a de-novo translocation t(6;7) (p11;p22) and a culture-derived anomaly (trisomy 2) found in amniotic fluid cells but not in the fetus aborted because it had spina bifida. Of the pregnancies complicated by constitutional abnormalities, only the pregnancy in which the de-novo translocation was detected was terminated. No chromosome abnormalities were detected in the 17 pregnancies which miscarried after amniocentesis. These results provide little justification for including fetal karyotyping as an essential part of maternal serum alpha-fetoprotein screening programmes.

Prenatal diagnosis of exstrophy of the cloaca

While screening for neural tub defects, three cases of exstrophy of the cloaca were found through elevated second-trimester maternal serum alphafetoprotein levels. Measurement of amniotic fluid alphafetoprotein and examination of the structure of rapidly adhering cells confirmed the abnormalities, and the pregnancies were terminated. Subsequent studies of cholinesterase isozymes by acrylamide electrophoresis showed an abnormal acetylcholinesterase band in each of the three amniotic fluids. During the same period, two more cases of exstrophy of the cloaca were identified in spontaneous abortions and another one in a stillbirth. It is suggested that the condition is more common than has been previously suspected and is often misclassified as omphalocele.

Alpha-fetoprotein: a review

Alpha fetoprotein (AFP) is the major protein of fetal serum and most resembles albumen, which replaces it shortly after birth. It is produced by fetal liver and passes into the amniotic fluid (AF) via fetal urine. A small amount crosses the membranes into the maternal circulation. Excluding fetal blood contamination, elevated AF/AFP levels indicate fetal demise or one of several abnormalities. Maternal serum (MS) AFP measurement can be used as a screening procedure to identify neural tube defects providing a rigorous protocol is followed. This requires that a laboratory establish its normal range of MS/AFP levels between 15 and 20 weeks gestation, employ a reliable assay with adequate controls, and has recourse to genetic counseling as well as expert sonography, amniocentesis and amniography if necessary. Pregnancy is the only normal situation in which AFP is present after birth. It may be present in high levels in certain malignancies and has been useful in monitoring their recurrence. This article will review the history, biochemistry, and different assays of AFP in AF and blood as well as the indications and limitations for their use.

Raised maternal serum alpha-fetoprotein levels and low birth weight babies

In a retrospective study of low birth weight babies (less than 2.5 kg) born in one year it was found that statistically more maternal serum alpha-fetoprotein levels were above twice the median level than a control group of mothers producing larger babies (more than 3 kg). However, from the results the test cannot be accepted as being a prospective indicator or as a screening test of low birth weight in pregnant women.

Maternal serum alpha-fetoprotein and birth weight

Maternal serum alpha-fetoprotein (AFP) levels between 16 and 18 weeks of pregnancy were studied in relation to birth weight among 4198 singleton pregnancies resulting in a liveborn or stillborn infant without a neural tube defect. The highest mean birth weight (3365 g) was found among infants born to women with AFP values in the range 0.50 to 0.74 times the normal median for the relevant week of gestation. As the AFP decreased from this level to less than 0.25 times the median, the birth weight decreased by 193 g and the proportion of infants weighing 2500 g or less increased from 4 per cent to 11 per cent. As the AFP level increased from 0.50 to 0.74 times the median to 3.0 times the median or greater, the birth weight decreased by 371 g and the proportion of infants weighing 2500 g or less increased from 4 to 22 per cent. The negative association was the more important of the two since the magnitude was greater and it affected 92 per cent of pregnancies. The positive association among women with low ARP levels was substantially reduced when the analysis was restricted to women who had spontaneous labours. It seems that this minor positive association arises mainly because women in whom gestation is over-estimated tend to have both a low AFP and, later, an apparently prolonged pregnancy leading to the elective delivery of an infant who is, in fact, born early.