Maternal serum alpha-fetoprotein in twin pregnancy

Point-of-Care Quantification of Serum Alpha-Fetoprotein for Screening Birth Defects in Resource-Limited Settings: Proof-of-Concept Study

Background:

Maternal serum alpha-fetoprotein (MSAFP) concentration typically increases during pregnancy and is routinely measured during the second trimester as a part of screening for fetal neural tube defects and Down syndrome. However, most pregnancy screening tests are not available in the settings they are needed the most. A mobile device–enabled technology based on MSAFP for screening birth defects could enable the rapid screening and triage of high-risk pregnancies, especially where maternal serum screening and fetal ultrasound scan facilities are not easily accessible. Shifting the approach from clinic- and laboratory-dependent care to a mobile platform based on our point-of-care approach will enable translation to resource-limited settings and the global health care market.

Objective:

The objective of this study is to develop and perform proof-of-concept testing of a lateral flow immunoassay on a mobile platform for rapid, point-of-care quantification of serum alpha-fetoprotein (AFP) levels, from a drop of human serum, within a few minutes.

Methods:

The development of the immunoassay involved the selection of commercially available antibodies and optimization of their concentrations by an iterative method to achieve the required detection limits. We compared the performance of our method with that of commercially obtained human serum samples, with known AFP concentrations quantified by the Abbott ARCHITECT chemiluminescent magnetic microparticle immunoassay (CMIA).

Results:

We tested commercially obtained serum samples (N=20) with concentrations ranging from 2.2 to 446 ng/mL to compare the results of our point-of-care assay with results from the Abbott ARCHITECT CMIA. A correlation of 0.98 (P<.001) was observed on preliminary testing and comparison with the CMIA. The detection range of our point-of-care assay covers the range of maternal serum AFP levels observed during pregnancy.

Conclusions:

The preliminary test results from the AFP test on the mobile platform performed in this study represent a proof of concept that will pave the way for our future work focused on developing a mobile device–enabled quad-screen point-of-care testing with the potential to enable the screening of high-risk pregnancies in various settings. The AFP test on the mobile platform can be applied to enable screening for high-risk pregnancies, within a few minutes, at the point of care even in remote areas where maternal serum tests and fetal ultrasound scans are not easily accessible; assessment of whether clinical follow-up and diagnostic testing may be needed after a positive initial screening evaluation; and development of surveillance tools for birth defects.

Imaging findings in association with altered maternal alpha-fetoprotein levels during pregnancy

Maternal serum alpha-fetoprotein is a valuable laboratory test used in pregnant women as an indicator to detect certain clinical abnormalities. These can be grouped into four main categories: fetal factors, pregnancy complications, placental abnormalities, and maternal factors. Imaging is an invaluable tool to investigate the various etiologies leading to altered maternal serum alpha-fetoprotein. By reading this article, the radiologist, sonologist, or other health care practitioner should be able to define the probable pathology leading to the laboratory detected abnormal maternal serum levels, thus helping the clinician to appropriately manage the pregnancy and counsel the patient.

A classic twin study of isolated gastroschisis

The etiology of gastroschisis remains elusive. A classic twin study was used to assess the relative contribution of environmental and genetic factors in its development. Screening of 4872 twin pregnancies identified three unreported twin pairs comprising two monozygous and one dizygous discordant pair of twins. Review of the literature identified an additional 21 twin pairs. We observed lower pair- and proband-wise concordance rates for monozygotic compared to dizygotic twin pairs, pair- and proband-wise concordance ratios below 1.0. Our results suggest environmental to play a greater role than genetic factors in the development of gastroschisis.

Familial recurrence of gastroschisis: literature review and data from the population-based birth registry "Mainz Model"

BACKGROUND

Familial forms of gastroschisis are considered rare. A search for these forms in a population-based birth registry in 1993 found a recurrence risk of 3.5% among first-degree relatives. Since then, similar investigations in population-based registries have led to contradictory results.

METHODS

A search of the population-based birth registry "Mainz Model" for familial cases of gastroschisis and a systematic review of the literature were performed.

RESULTS

The Mainz Model database yielded 1 familial recurrence out of 27 gastroschisis cases. From the literature, 37 affected families could be retrieved. Among 412 gastroschises from population-based registries, 10 familial recurrences have been found. These translate into a recurrence risk of 2.4%, with a strong tendency toward underestimation.

CONCLUSION

The existing data support the hypothesis that familial recurrence of gastroschisis is much more likely than previously thought.

Pregnancy characteristics and maternal breast cancer risk: a review of the epidemiologic literature

The short- and long-term effects of pregnancy on breast cancer risk are well documented. Insight into potential biological mechanisms for these associations may be gained by studying breast cancer risk and pregnancy characteristics (e.g., preeclampsia, twining), which may reflect hormone levels during pregnancy. To date, no review has synthesized the published literature for pregnancy characteristics and maternal breast cancer using systematic search methods. We conducted a systematic search to identify all published studies. Using PUBMED (to 31 July 2009), 42 relevant articles were identified. Several studies suggest that multiple births may be associated with a lowered breast cancer risk of about 10-30%, but results were inconsistent across 18 studies. The majority of 13 studies suggest about a 20-30% reduction in risk with preeclampsia and/or gestational hypertension. Six of seven studies reported no association for infant sex and breast cancer risk. Data are sparse and conflicting for other pregnancy characteristics such as gestational age, fetal growth, pregnancy weight gain, gestational diabetes, and placental abnormalities. The most consistent findings in a generally sparse literature are that multiple births and preeclampsia may modestly reduce breast cancer risk. Additional research is needed to elucidate associations between pregnancy characteristics, related hormonal profiles, and breast cancer risk.

Management of Multiple Pregnancy: Prenatal Care???Part I

Over the past 20 years, the number and rate of multiple births have dramatically increased in the United States. The rise in multiple births is mainly attributable to the increased use of ovulation-inducing drugs and the newly developed assisted reproductive technologies such as in vitro fertilization. Multifetal gestation is associated with an increased risk of perinatal morbidity and mortality. Multiple births account for an increasing percentage of low-birth-weight infants, preterm births, and infant mortality. In this section, we address the management of the multifetal pregnancy, focusing on the maternal physiology, the diagnosis, the pregnancy outcomes, and the antenatal management of multiple gestation.

TARGET AUDIENCE

Obstetricians & Gynecologists, Family Physicians

LEARNING OBJECTIVES

After completion of this article, the reader should be able to describe the effects of the rising rate of multiple pregnancies on perinatal morbidity and mortality, to recall the complications of diagnosing and treating abnormalities of multiple pregnancies, and to list the many changes that occur in both the mother and the fetuses in multiple pregnancies.

Reproductive factors and extreme levels of maternal serum alpha-fetoprotein: a population-based study

BACKGROUND

Levels of maternal alpha-fetoprotein (AFP) are increased during multiple gestations and preeclampsia but little is known regarding AFP levels in relation to other reproductive factors. Consequently, the objective of this work was to describe the possible relationship between AFP levels during pregnancy and maternal age at birth, maternal age at first birth, parity, time since previous birth and gender of the offspring.

METHODS

Based on national registries we obtained the reproductive history on a population-based cohort of 44 227 women who had serum AFP levels determined in gestational weeks 14-21 and whose present and previous pregnancies resulted in live-born singletons.

RESULTS

Many previous births and an interval of less than 2 years since last birth were significantly associated with extremely low levels of AFP in the mother. However, age at first birth and age at present pregnancy did not influence the AFP level. Women who gave birth to a girl had AFP levels that were 5%[95% confidence interval (CI) 4-6%] lower than those of women who had a boy. Adjustment for birthweight did not significantly affect the estimate.

CONCLUSIONS

Low serum AFP levels in pregnancy are significantly correlated with high parity and with a short interval between births. The significantly lower levels of AFP in women who gave birth to girls could indicate a possible gender-specific regulatory mechanism.

Midtrimester maternal serum screening after multifetal pregnancy reduction in pregnancies conceived by in vitro fertilization

PURPOSE

Data about the effect of multifetal pregnancy reduction on midtrimester maternal serum levels of alpha-fetoprotein (AFP), human chorionic gonadotropin (hCG), and unconjugated estriol (uE3) are scarce and contradictory. Differing gestational ages at fetal reduction, transvaginal versus transabdominal needle insertion, and injection of different feticidal agents compound the analysis of published data.

METHODS

We examined clinical and laboratory data about 27 high-order gestations that were reduced to twins in the first trimester. Fetal reductions were performed transabdominally at 11.41 +/- 1.15 weeks' gestation by fetal intrathoracic injection of KCl, and maternal blood sampling was performed at 16.48 +/- 1.05 weeks. "Pseudo-risks" for singleton pregnancies were calculated by correcting serum analyte levels for twins.

RESULTS

Twenty-four (88.9%) of 27 patients had maternal serum AFP levels above 2.0 MoM (mean, 4.60 +/- 3.48 MoM; range, 1.49-14.85 MoM), however, none of the newborns had structural anomalies. AFP serum levels did not correlate with the number of reduced fetuses or with adverse obstetric outcome. The mean hCG levels were 1.22 +/- 0.49 MoM (range, 0.14-2.47), and the mean uE3 levels were 1.15 +/- 0.31 MoM (range, 0.56-1.84). Based on maternal age alone, seven patients (25.9%) would have been offered amniocentesis for a term Down syndrome risk greater than 1:384, whereas combined risk calculations with hCG and uE3 levels resulted in 1 (3.7%) screen-positive case (P < 0.01).

Ambulatory management of multiple gestation

Ambulatory management of multiple gestation requires careful and continuing care by the obstetrician. The initial evaluation should include a comprehensive history, including use of fertility enhancing drugs and ART, family history, social history; a general physical examination, including a pelvic examination; laboratory evaluation, including complete blood cell count, dipstick urinalysis for protein and glucose, urine culture, blood type, Rh factor and irregular blood antibody determination, serology for rubella, syphilis, hepatitis B surface antigen and varicella (if there is no history). A Papanicolaou smear should be done at the time of the pelvic examination, as should evaluation for bacterial vaginosis. Ultrasound assessment of placentation should be done at 14 weeks' gestation, but vaginal or perineal ultrasound of cervical length should be done at the initial visit. Other testing procedures should include repeat ultrasound evaluation for fetal growth every 4 weeks in a dichorionic placentation and every 3 weeks if monochorionic placentation is present. Triple screen MSAFP at 16-18 weeks' gestation and blood sugar screening at 22-26 weeks should be performed. After the first trimester, the patient should schedule physician visits every 2 weeks or less. Routine medications should include one prenatal vitamin per day, additional folic acid supplementation of 1.0 mg per fetus, supplemental iron preparation, and additional calcium to equal 1500 mg/day. The use of low-dose aspirin to prevent preeclampsia in twin gestations has not been adequately studied. Continuing vigilance by the knowledgeable obstetrician should occur. Multiple gestations should not be cared for by non-physician providers or by family physicians. Referral to a maternal-fetal medicine unit is recommended.

Prenatal care and multiple pregnancy

Prenatal care of multiple pregnancy presents a variety of nursing challenges. Specialized care, beginning in early pregnancy, can have a significant impact on the outcome for mothers and neonates. Dramatically increasing roles for advanced technology in the care of multifetal pregnancies must be balanced with families' needs for education and support.

Antenatal screening for Down's syndrome

BACKGROUND

In 1968 the first antenatal diagnosis of Down's syndrome was made and screening on the basis of selecting women of advanced maternal age for amniocentesis was gradually introduced into medical practice. In 1983 it was shown that low maternal serum alpha fetoprotein (AFP) was associated with Down's syndrome. Later, raised maternal serum human chorionic gonadotrophin (hCG), and low unconjugated oestriol (uE3) were found to be markers of Down's syndrome. In 1988 the three biochemical markers were used together with maternal age as a method of screening, and this has been widely adopted. PRINCIPLES OF ANTENATAL SCREENING FOR DOWN'S SYNDROME: Methods of screening need to be fully evaluated before being introduced into routine clinical practice. This included choosing markers for which there is sufficient scientific evidence of efficacy, quantifying performance in terms of detection and false positive rates, and establishing methods of monitoring performance. Screening needs to be provided as an integrated service, coordinating and managing the separate aspects of the screening process. SERUM MARKERS AT 15-22 WEEKS OF PREGNANCY: A large number of serum markers have been found to be associated with Down's syndrome between 15 and 22 weeks of pregnancy. The principal markers are AFP, hCG or its individual subunits (free alpha- and free beta-hCG), uE3, and inhibin A. Screening performance varies according to the choice of markers used and whether ultrasound is used to estimate gestational age (table 1). When an ultrasound scan is used to estimate gestational age the detection rate for a 5% false positive rate is estimated to be 59% using the double test (AFP and hCG), 69% using the triple test (AFP, hCG, uE3), and 76% using the quadruple test (AFP, hCG, uE3, inhibin A), all in combination with maternal age. Other factors that can usefully be taken into account in screening are maternal weight, the presence of insulin dependent diabetes mellitus, multiple pregnancy, ethnic origin, previous Down's syndrome pregnancy, and whether the test is the first one in a pregnancy or a repeat. Factors such as parity and smoking are associated with one or more of the serum markers, but the effect is too small to justify adjusting for these factors in interpreting a screening test.

URINARY MARKERS AND FETAL CELLS IN MATERNAL BLOOD

Urinary beta-core hCG has been investigated in a number of studies and shown to be raised in pregnancies with Down's syndrome. This area is currently the subject of active research and the use of urine in future screening programmes may be a practical possibility. Other urinary markers, such as total oestriol and free beta-hCG may also be of value. Fetal cells can be identified in the maternal circulation and techniques such as fluorescent in situ hybridisation can be used to identify aneuploidies, including Down's syndrome and trisomy 18. This approach may, in the future, be of value in screening or diagnosis. Currently, the techniques available do not have the performance, simplicity, or economy needed to replace existing methods.

DEMONSTRATION PROJECTS

Demonstration projects are valuable in determining the feasibility of screening and in refining the practical application of screening. They are of less value in determining the performance of different screening methods. Several demonstration projects have been conducted using the triple and double tests. In general, the uptake of screening was about 80%. The screen positive rates were about 5-6%. About 80% of women with positive screening results had an invasive diagnostic test, and of those found to have a pregnancy with Down's syndrome, about 90% chose to have a termination of pregnancy. ULTRASOUND MARKERS AT 15-22 WEEKS OF PREGNANCY: There are a number of ultrasound markers of Down's syndrome at 15-22 weeks, including nuchal fold thickness, cardiac abnormalities, duodenal atresia, femur length, humerus length, pyelectasis, and hyperechogenic bowel. (ABSTRA

Second-trimester maternal serum alpha-fetoprotein, human chorionic gonadotropin, and unconjugated oestriol after early transvaginal multifetal pregnancy reduction

Maternal serum alpha-fetoprotein (MSAFP), human chorionic gonadotropin (hCG), and unconjugated oestriol (UE3) are used as second-trimester screening markers for the detection of various fetal abnormalities. Previous studies have suggested that second-trimester MSAFP is consistently elevated after late first-trimester transabdominal multifetal pregnancy reduction (MFPR). The present study was undertaken to evaluate the levels of all three markers after early transvaginal MFPR. Maternal serum was examined for MSAFP, hCG, and UE3 at 16-18 weeks' gestation in 28 patients who underwent transvaginal MFPR at approximately 10 weeks' gestation. The mean interval between the reduction procedure and the screening test was 7.2 +/- 0.9 weeks. The mean MSAFP value in 24 patients carrying viable twins was 2.49 +/- 0.99 multiples of the median (MOM). Two patients had elevated MSAFP values: one in association with omphalocoele and the other in relation to an adverse pregnancy outcome. All but two patients had normal hCG values (mean 1.98 +/- 1.26 MOM). Two cases with elevated hCG were associated with an adverse pregnancy outcome. Unconjugated oestriol values were within the normal range in all patients (mean 1.69 +/- 0.61 MOM). These results suggest that early transvaginal MFPR, at approximately 10 weeks' gestation, does not appear to influence second-trimester MSAFP, hCG, and UE3 levels. The values of these markers may therefore be interpreted by using the same criteria as those for the general obstetric population.

Enhanced twin pregnancy detection within an open neural tube defect and Down syndrome screening protocol using free-beta hCG and AFP

We have applied our multimarker approach of maternal serum alpha-fetoprotein (AFP) and free-beta human chorionic gonadotropin (hCG) for Down syndrome screening to multiple gestations to assess its efficacy for improved detection of twin and triplet pregnancies. This study matched 225 cases of twin pregnancy and 39 cases of triplet pregnancy each with ten singleton pregnancies based on gestational week, race, time to receive sample, time of year of sample, and geographical area. The ratios of the MOM for each group at the tenth, 50th, and 90th percentiles were compared by the Wilcoxon test. Risks for twins were calculated using Bayes' rule, the age-related incidence of twins, and the levels of AFP and free-beta hCG. The tenth, 50th and 90th percentiles of free-beta hCG MOMs in twin and triplet cases were 0.85, 1.99, and 4.51, and 1.38, 2.78, and 4.07, respectively. For AFP, the MOMs at these percentiles were 1.26, 1.91, and 2.99, and 2.02, 2.68, and 5.30, respectively. The twin and triplet distributions for each marker were statistically significantly different from the singleton distributions (P < 0.0001) and from each other (P = 0.0012). At a twin risk cut-off of 1 in 50, 77.4 per cent of all twin gestations can be detected in a second-trimester AFP and free-beta hCG screening protocol with 5.1 per cent of singleton pregnancies falsely identified as at risk for twins. Our dual marker protocol for mid-trimester pregnancy screening combining AFP and free-beta hCG can identify over 77 per cent of twin pregnancies in women less than 35 years of age. This benefit may contribute to an improved outcome of pregnancy by early detection of multiple gestation.

Monozygotic twins discordant for gastroschisis: case report and review of the literature of twins and familial occurrence of gastroschisis

We describe a pair of monozygotic (MZ) female twins discordant for gastrochisis. To our knowledge, this is the first such case reported. The zygosity was verified by DNA analysis using highly polymorphic microsatellites. There was no family history of gastroschisis. During pregnancy there was no suspicion of any exposure responsible for the malformation. The number of twin cases described so far does not allow any conclusion as to hereditary factors in the cause of gastroschisis, but the number of families reported with familial gastroschisis suggests that the recurrence risk is higher than previously thought.

Breast cancer risk in mothers of multiple births

Data from an international case-control study of breast cancer that was conducted in the 1960s were used to examine whether multiple births affect the risk of breast cancer in the mother. Among 2821 parous breast-cancer patients, 88 had had one or more multiple births, whereas among 8882 controls 247 had had one or more multiple births; the logistic-regression-adjusted odds ratio (OR) was 1.21, the 95% confidence interval (CI), 0.94 to 1.55. The OR was significantly elevated during the 15-year period following the latest multiple birth (1.76; CI, 1.12 to 2.75), but declined toward the null afterwards. A late first pregnancy imparted a substantially higher breast-cancer risk when it was multiple rather than singleton; the OR was 2.34 for a multiple and 1.48 for a singleton first pregnancy when the cutoff point was 30 years, and 4.58 and 1.57, respectively, when the cutoff point was 35 years. Since multiple pregnancies are characterized by higher levels of pregnancy estrogens, the results of this study would be compatible with the hypothesis that these hormones may be responsible for the transient increase in breast-cancer risk following a term pregnancy and, in particular, a multiple term pregnancy. The long-term reduction of breast-cancer risk is probably due to a different mechanism, most likely the terminal differentiation of susceptible mammary-gland cells.

Maternal serum human chorionic gonadotropin levels in twin pregnancies

Introduction of combined screening with maternal serum alpha-fetoprotein and human chorionic gonadotropin (MShCG) assays for fetal chromosome defects requires establishment of the normal range for twins. This report documents that the normal range for MShCG between 15 and 19 weeks in twin gestations was 1.84-2.41 multiples of the singleton median. Of the 192 twin pregnancies studied, 31.7 and 47.9 per cent had MShCG values greater than or equal to 2.5 and greater than or equal to 2.0 multiples of the singleton median, respectively.

A co-twin fetus papyraceus as a cause of elevated AFP and acetylcholinesterase in the amniotic fluid of the normal co-twin

An elevated amniotic fluid alpha-fetoprotein (AF-AFP) level together with a positive acetylcholinesterase (AChE) band is strongly predictive of neural tube defect (NTD) in the fetus. We report such results in a pregnancy in which the fetus was found to be normal after termination. Among the placental fragments was found a sac containing a prenatally undetected co-twin fetus papyraceus. We suggest that pregnant women with such laboratory results but lacking sonographic evidence of NTD should have a high-level untrasonographic investigation, as well as a thorough pathologic examination of both placenta and fetus in cases of termination.