Down's syndrome screening: a controversial test, with more controversy to come!

Informing on prenatal screening for Down syndrome prior to conception. An empirical and ethical perspective

In most Western countries, information on prenatal screening for Down syndrome is provided in the first-trimester of pregnancy. The purpose of this study was to examine whether this information should additionally be provided before pregnancy to improve the informed decision-making process. In an empirical study, we obtained data from pregnant women with respect to their preferences regarding information on prenatal screening preconceptionally. Questionnaire data (n = 510) showed that 55.7% of responding women considered participating in prenatal screening for Down syndrome before pregnancy. 28.0% of women possessed information on prenatal screening preconceptionally. 84.6% preferred not to receive information preconceptionally in retrospect. In an ethical analysis, we elaborated on these preferences by weighing pros and cons. We considered two arguments against the provision of information on prenatal screening preconceptionally: women's preference to receive information in a step-by-step manner, and the risk of providing a directive message. We identified three reasons supporting its provision preconceptionally: the likelihood of making an informed decision could, firstly, be increased by "unchaining" the initial information from possible subsequent decisions, and, secondly, by providing women sufficient time to deliberate. Thirdly, the probability of equal access to prenatal screening may increase. To conclude with, we propose to incorporate an information offer on prenatal screening for Down syndrome in preconception care consultations. By offering information, instead of providing information, prospective parents are enabled to either accept or decline the information, which respects both their right to know and their right not-to-know.

Effects of Serum-Clot Contact Time on Second-Trimester Prenatal Screening Markers and their Stability in Serum

Alpha-fetoprotein, human chorionic gonadotropin and unconjugated estriol are screening markers for fetal trisomies and structural disorders of the neural tube defect type. Determination of these biochemical markers is performed in laboratories that receive samples, serum or blood, and sample preparation as well as transport conditions may affect analyte stability and test results. The effect of serum-clot contact time prior to centrifugation (30, 60, 90, 120 minutes and 24 hours) was examined for serum values of alpha-fetoprotein, human chorionic gonadotropin and unconjugated estriol, as well as their stability in serum samples over periods of up to five days at 2-8 °C, and 30 days at -20 °C. No statistically significant difference was found for analyte values in serum obtained by centrifuging blood samples after serum-clot contact times of 30, 60, 90 and 120 minutes at room temperature and 24 hours at 2-8 °C, i.e. there is a 24-hour tolerance for prolonged serum-clot contact. Alpha-fetoprotein and free estriol serum values do not show statistically significant changes over a period of 5 days at 2-8 °C. Similarly, serum freezing does not affect alpha-fetoprotein and free estriol values. As for human chorionic gonadotropin values showing statistical differences where serum is stored at both +4 °C and at -20 °C, their levels are concentration-dependent. Free estriol serum values at +4 °C over the time period of 5 days showed statistically significant differences.

The ethics of antenatal screening: lessons from Canute

Modern medicine has given us the power to identify many diseases before they occur and apply preventative measures so that morbidity and mortality may be avoided. When these screening measures are offered to someone who is capable of making an informed decision to proceed, they may be uncontroversial but may actually cause more harm than good. In antenatal screening, it is difficult to define who the patient is, because there are several possibilities: the pregnant woman, the foetus, or the family. Consequently, it can be difficult to identify whether the treatment offered is in the best interest of all concerned. Our growing knowledge about the human genome will in future give us more power to be able to identify undesirable traits, but there is no strict definition where the line of acceptability lies. The eugenic excesses of the mid-20(th) century are often cited as a reason why antenatal screening is bad. The story of King Canute informs us that defining a 'line in the sand' cannot prevent the rising tide of medical capability overwhelming any arbitrary level of acceptability. This paper discusses the history of eugenics from Sparta to the modern day and attempts to give some perspective on this crucial policy area. No one paper can provide the answer: it is necessary that society as a whole debates where it wishes to go...

Hyperglycosylated hCG

Hyperglycosylated hCG (hCG-H) is a glycosylation variant of the hormone hCG. Here we review all that is known about this independently functioning molecule. As discussed, it is a very different molecule to the hormone hCG. First, hCG-H is produced by cytotrophoblast cells while regular hCG is made in syncytiotrophoblast cell. Second, it is an autocrine acting directly on the cells which produce it, while regular hCG is an endocrine acting on maternal corpus luteal cells. Third, hCG-H has minimal biological activity in promoting progesterone production compared to regular hCG. Fourth, hCG-H functions unlike regular hCG as an invasion promoter, whether invasion as in choriocarcinoma and testicular germ cell malignancies, or as in implantation of pregnancy. These functions seemingly occur through action on cytotrophoblast cell TGFbeta receptors. Fifth, hCG-H is an essential component for successful human implantation to prevent early pregnancy loss and spontaneous abortion. Sixth, hCG-H is critical for promoting the midtrimester hemochorial implantation, and for preventing preeclampsia. Seventh, measurements of hCG-H have advantages over measurements of regular hCG or total hCG, in detecting pregnancy, pregnancy outcome (failing or term pregnancy), predicting preeclampsia in pregnancy, or as a tumor marker for gestational trophoblastic diseases.

Hyperglycosylated hCG: a variant with separate biological functions to regular hCG

Hyperglycosylated hCG (hCG-H) is an over-glycosylated variant of hCG. While regular hCG is produced by differentiated syncytotrophoblast cells, hCG-H is independently secreted by stem cytotrophoblast cells. hCG-H has an independent function to regular hCG. It is the direct promoter of trophoblast invasion and malignancy. Invasion as in implantation of pregnancy and malignancy as in choriocarcinoma. Neither will occur in the absence of hCG-H. hCG-H measurements have multiple functions. Primarily or exclusively hCG-H is produced at the time of implantation of pregnancy and in the 2 weeks that follows. As such, a good pregnancy test should measure regular hCG and hCG-H equally. This is not commonly the case. Most tests poorly detect hCG-H. New pregnancy tests are needed, including those that measure only hCG-H. Considering that hCG-H is critical for implantation, hCG-H is also invaluable for determining pregnancy outcome and detecting failures. It makes a considerable more accurate test for detecting pregnancy failures and ectopic pregnancies than regular hCG. Down syndrome pregnancies are marked by poor trophoblast differentiation. As such, they are very well marked by using a combination of hCG-H measurements and other screening tests. hCG-H is also an absolute tumor marker for malignant or invasive gestational trophoblastic disease, it can discriminate active and inactive (quiescent) disease, and the need for chemotherapy.