Role of chromosomal abnormalities in pregnancy complications

Role of chromosomal abnormalities in pregnancy complications

Chromosomal abnormalities mainly affect early fetal development, placental function and structural integrity of fetal body systems.

That’s why chromosomal abnormalities lead to problems with fetal growth and congenital anomalies.

The most common presentation of chromosomal abnormalities in early pregnancy is pregnancy loss (miscarriage).

1. Early pregnancy loss:

• Errors of chromosomal distribution during cell division leading to abnormal number of chromosomes.
• Embryos become non-viable
• Up to 75% of early pregnancy loss is due to abnormal chromosomes
• The most common are: trisomy 16 and turner syndrome

2. Recurrent miscarriage:

• Chromosomal rearrangements of parental chromosomes lead to repeated pregnancy loss.

3. Birth defects:

• Down syndrome (errors in chromosome 21): heart defects and intellectual disability
• Edwards syndrome (errors in chromosome 18): severe developmental delay and high neonatal mortality
• Patau syndrome (errors in chromosome 13): brain and fascial abnormalities
• Usually, chromosomal abnormalities present with congenital anomalies affecting multiple organ systems.

4. Restriction of fetal growth:

• Chromosomal abnormalities impair placental function
• This leads to restrictions of fetal growth with poor outcome

5. Intrauterine fetal death:

Chromosomally abnormal fetuses are more prone to die inside the womb

6. Placental abnormalities:

• Poor implantation and preeclampsia can be caused by chromosomal abnormalities

7. Molar pregnancy results because of abnormal chromosomal fertilization leading to abnormal placental tissue growth instead of a viable fetus.

8. Infertility:

• Because placental abnormalities lead to prevention of embryo implantation and sometimes early pregnancy loss before even knowing that the lady is pregnant.

How to screen for chromosomal abnormalities?

• Measuring nuchal translucency in the first trimester
• Blood biochemical markers
• Cell free fetal DNA testing
• Combination of these methods with each other and with maternal age

How to diagnose chromosomal abnormalities in pregnancy?

• Chorionic villus sampling: taking a placental sample and culturing it in the laboratory to study fetal cells chromosomes
• Amniocentesis: taking a sample from amniotic fluid and culturing it in the laboratory to study fetal cells chromosomes
• Karyotyping/ genetic testing of products of conception after miscarriage or pregnancy termination

Is there a way to prevent pregnancy with chromosomally abnormal fetuses?

Yes, through invitro fertilization and testing fetal chromosomes before transferring them inside the uterus, but this doesn’t guarantee that the pregnancy won’t have any complications such as miscarriage or congenital anomalies or other above-mentioned complications that might happen due to other causes besides chromosomal abnormalities.

Dr Najeeb Layyous  F.R.C.O.G

Consultant Obstetrician, Gynecologist and Infertility Specialist