Diagnostics during pregnancy, and termination

Question

Is there an option of doing diagnostics as early as possible during pregnancy so that a regular termination would be possible, or would/will it always be a late termination? In other words, does one always have to have a stillbirth, or is there any method that will provide a result early enough to have a termination with curettage around the 12th week?

This new blood test to diagnose down syndrome early – is there something similar for CF as well?

My husband and I are both gene carriers and already have a child with CF.

Answer

Hello,

You are asking about options of early, prenatal diagnostics that can show whether a child has CF or not. You are saying that you and your husband are both gene carriers for CF and already have a child with CF.

Based on heredity rules for CF, for a couple who are both healthy CF gene carriers, there is a 25% chance in each pregnancy that their child will have CF. In 50% of pregnancies, a healthy gene carrier can be born, and a healthy child without genetic CF features in 25%.

Prenatal diagnostics in the context of CF certainly involve so-called pre-implantation diagnostics (PID). This was not approved in Germany until recently but is now allowed and regulated by a strict law. PID is a form of prenatal diagnostics which, however, can only be carried out in connection with extracorporeal fertilization methods such as IVF or ICSI.

Let me briefly explain what IVF and ICSI are:

- IVF (in-vitro fertilization) is an extracorporeal fertilization method. The sperms are finding the way to the ovum themselves in a test tube

- ICSI (intracytoplasmic sperm injection) is an extracorporeal fertilization method as well. Here, a single sperm is injected into the ovum under the microscope.

In PID, two cells are taken from a multi-cell embryo and can be examined for a certain gene defect. If this gene defect is not found, the embryo can be placed into the uterus. It can not be ruled out that the child might have other diseases, though. Due to the methodical effort involved, this procedure should only be an option for couples for whom the risk of having a child with CF is at 50% and who will have to undergo IVF or ICSI treatment anyway.

A further form of PID in connection with IVF/ICSI is the examination of a fertilized ovum’s polar bodies. However, this only allows conclusions about the maternal DNA of the ovum (which is usually already known), so that this test does not provide any additional information.

One prenatal diagnostic method for CF is chorionic villus sampling (CVS). Here, tissue from the future placenta (chorinonic villi) of the embryo is taken. This is aspirated with a hollow needle inserted through the vagina and the cervical channel and then genetically tested. If the sampling is done too early, there might not be enough tissue available, so that the ideal time to do this test is after the 11th week of pregnancy.

Concerning you question about the blood test for early diagnosis of down syndrome: I assume you are referring to the still highly controversial MaterniT21 test. To my knowledge and according to the literature I consulted, there is no comparable test for early diagnosis of CF.

Kind regards
Dr. Christina Smaczny

02.08.2012