By Neus Ferrando Gilabert BSc, MSc (embryologist).
Last Update: 09/23/2015

Since regular prenatal care and hospital delivery have been established, perinatal mortality has fallen significantly among industrialized societies. These rates prove to be even more remarkable if compared to maternal and infant mortality rates of underdeveloped or developing countries.

That is why a regular medical control throughout gestation and hospital delivery are the main important factors to avoid fetal and perinatal problems.

In fact, experts state that bringing labor at home, despite being defended by some groups, should be avoided. It is not about turning childbirth into a medical process but about preventing many problems the fetus may experience. Such problems may appear or are detected before, during, and after labor.

Hospital delivery and its medical monitoring have drastically reduced the perinatal mental deficiency rate. This has been possible thanks to the many cutting-edge biochemical and genetic tests that are performed on the mother to avoid risks in the fetus. Just to name a few: triple screen test, cytogenetic study by amniocentesis, analysis of chorionic villus, and cordocentesis.

Triple screen test

Biochemical tests known as triple screen test or multiple marker screening (a.k.a quad screen or maternal serum screening) consist of analyzing the woman at the following levels:

  • Personal data such as the mother’s age, weight, number of fetuses, etc.
  • Ultrasound measurement: nuchal fold thickness (nuchal translucency scan or NT scan), amount of fluid in that area of the baby’s neck, and gestational age are analyzed.
  • Analysis of the following three biochemical markers based on a blood sample from the mother: alpha-fetoprotein (AFP), free beta-hCG, and estriol (E3).

The triple screen test is usually performed between weeks 10 and 13. Once obtained, the values are compared to a series of charts based on a pattern of values considered as normal for that week of pregnancy.

The result of this test will allow us to suspect or glimpse the presence of certain altered fetal growth patterns:

  • Increased maternal levels of AFP values may indicate the woman is carrying a multiple birth or the presence of spina bifida or anencephaly in the fetus. Conversely, decreased levels of AFP are indicative of trisomy 21 or 28.
  • Decreased levels of free or unconjugated estriol raise suspicions of chromosomal alterations in chromosomes 13, 18, or 21.
  • Any alteration in the beta hCG protein levels may indicate the presence of chromosomal abnormalities. Increased levels of this protein are usually associated with the development of the Down syndrome (DS or DNS) in the fetus.

MoMs (multiple of the median) are the units of measurement used for this analysis. MoMs are used to generalize the units of the above mentioned values and avoid deviations related to the gestational age. Results between 0.5 and 2.5 MoMs are considered to be within the average. Besides, 1 MoM is the value qualified as normal; therefore, the greater the deviation from this value is, the worse the result will be.

For instance, we can get a glimpse of possible fetal development alterations if nuchal translucency values are above 1.8, values of AFP and beta-hCG are below 0,5 or over 2,5 and estriol levels are under 0.5.

Cytogenetic study

A karyotype cytogenetic study has precise indications:

  • Maternal advanced age (over age 35)
  • Abnormal results of the triple screen test.
  • Existence of recurrent miscarriages
  • Previous children with chromosome abnormalities
  • Family history of diseases

When performing a karyotyping of fetal cells, it will be necessary to carry out one of the following invasive techniques: amniocentesis, chorion biopsy, or cordocentesis (a.k.a. Percutaneous Umbilical Cord Blood Sampling or PUBS). The choice of a particular type of technique depends on each case.

  • Amniocentesis: it consists of removing a sample of amniotic fluid through the abdominal wall by means of a very fine needle and ultrasound scan. It is usually performed from week 15 of gestation onwards. Also worth noting is the fact that it is an invasive technique, that is, it comprises a series of risks related to fetal damage and/or miscarriage.
  • Analysis of the chorionic villus: also called chorion biopsy, it consists in obtaining placental villus vaginally or transabdominally by an ultrasound control. This test can be performed prior to amniocentesis, on week 11 or 12 of gestation. Nevertheless, it is more complex and involves more risks than amniocentesis.
  • Cordocentesis or PUBS: through this technique, fetal blood is obtained by puncturing the vessels of the umbilical cord with a needle guided by ultrasound.

In all three cases, the chromosomal regions are identified, by fluorescence, analyzing whether they are correct or not.

The risk of mental deficiency has decreased from 25 to 5% in the past few years thanks to these medical studies, medical monitoring, and advice.

Maternal blood screening test

It is a non-invasive technique by which the risks derived from other tests such as amniocentesis are reduced. This is so because it works by analyzing the fetal DNA from a maternal blood sample with the aim of determining whether there is any genetic abnormality.

It has been proved that the mother’s bloodstream contains fetal cells, which allows us to obtain and analyze genetic information of the developing fetus. However, fetal cells in maternal circulation are only found in small quantities. This makes the process way more difficult, since fetal cells have to be separated from maternal circulation.

This cutting-edge sort of prenatal testing is becoming increasingly common nowadays among pregnant women both because it is comfortable and free from risks either from the fetus or the mother-to-be.

Authors and contributors

 Neus Ferrando Gilabert
BSc, MSc
Bachelor's Degree in Biology from the University of Valencia (UV). Postgraduate Course in Biotechnology of Human Assisted Reproduction from the Miguel Hernández University of Elche (UMH). Experience managing Embryology and Andrology Labs at Centro Médico Manzanera (Logroño, Spain). More information


    1. rose kobe

      Hi everyone!

      Cytogenetic studies are only performed under the conditions you mention here? And what about if I want to undergo it but neither of that situations match with mine? I’d like to do so just as a prevention measure, is it possible or not?

      Thank you very much

      • Sandra FernándezBA, MA

        Dear Rose,

        Cytogenetic studies entail many risks; therefore, if you’re not carrying a high risk pregnancy, there’s no need to perform any of them, because chances for miscarriage are higher.

        Best wishes.