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Can Hirschsprung's be detected Before Birth?

Except in cases of some very rare syndromes, there currently is no way to definitively know that a child has Hirschsprung disease (HD) before birth.  However, for families where one person already has HD, there may be information available during pregnancy about whether the baby is at high or low risk to have HD.  There are rare reports of bowel differences seen on ultrasound in children who have HD, but it is generally accepted that HD cannot be seen by prenatal ultrasound or other routine prenatal testing.  The information available to families with an affected individual may be from two sources.  Families may find out more about their average chances of having another child with HD based on their family medical history.  They also may be able to receive more precise and family specific information through genetic testing in some cases.  Each of these types of information is discussed in detail below.

The information about estimated chances of having a child with HD based on family medical history comes from a study published in 1990 by Badner et al.  The study looked at a large number of families where one or more individuals had HD. The researchers then looked for factors that affected the chances that more than one individual was affected.  They found that factors such as the length of colon affected, the gender of the affected individual and the gender of the future child were all important.  They then grouped families by these factors and calculated average chances that a second child with HD was born to families in each group.  These estimated chances are presented in Table 1 below.  Please note that the numbers given are averages, so any one family’s chance may be higher or lower than what is in the table.  Also, the numbers in this table do not apply to families where there is more than one individual with HD already, where HD is part of a syndrome, or with some other family or medical histories.  A genetic counselor or geneticist can determine whether these numbers apply well to a family by taking a detailed medical and family history, and then discuss the information with the family.

Table 1.

 

Recto-sigmoid segment

Colonic segment

Long segment

 

Male

Female

Male

Female

Male

Female

Siblings of Affected Males

4-5%

1%

9-10%

7%

9-12%

7-9%

Siblings of Affected Females

5-6%

1-2%

12-13%

10%

21-24%

17-19%

Children of Affected Males

0-1%

<1%

10-11%

8-9%

16-19%

12-14%

Children of Affected Females

0-1%

<1%

14-15%

11%

27-29%

21-22%

*Adapted from, Badner, J et al., A Genetic Study of Hirschsprung Disease. Am J Hum Genet. 46:568-580, 1990 (Table 8). Recto-sigmoid segment includes a lack of ganglion cells from the rectum up to any location in the sigmoid colon. Colonic segment includes lack of ganglion cells from the rectum up to the splenic flexure. Long segment includes lack of ganglion cells from the rectum to anywhere beyond the splenic flexure. For more information about this table and how to read it, please visit http://chakravarti.igm.jhmi.edu/AravindaChakravartiLab/Disease_Genetics1.html.

More precise and family specific information may be available if genetic testing is able to identify a genetic change that caused HD in an affected family member(s).  With current testing, a genetic change is not able to be found in all individuals with HD.  The chances of finding a causative genetic change are greater if there are multiple affected members in a family or if the affected individual in a family has long segment disease.  However, genetic changes may also be found in short segment cases.  A genetic counselor or geneticist can discuss the chances of finding a change and arrange genetic testing. 

If a genetic change is found, better information about chances of recurrence would be available.  Also, future pregnancies in that family would be able to be tested for that change.  The testing during pregnancy could be done by a procedure called Chorionic Villus Sampling (CVS) done at 10-13 weeks of pregnancy or by amniocentesis done from 14 weeks on (though rarely done after 18-20 weeks). There is also the possibility of testing embryos created by IVF for the genetic change before they are implanted (called Preimplantation Genetic Diagnosis, PGD), though a lab may need to be asked to develop this test.  Testing for the presence of the genetic change would be very accurate.  However, how effective the test is at predicting whether or not a fetus or embryo has HD depends upon two factors: 1) how certain the lab is that the genetic change found in the affected family member is disease causing (we don't always know the effect of every genetic change), and 2) what the chances are that anyone who inherits the genetic change will have HD (often not everyone who has a genetic change associated with HD will have the disease).   These factors will vary by family and the specific genetic change identified.  In general, we cannot know with 100% certainty that a fetus has HD, but if a fetus has a disease causing genetic change we would know they were at increased risk to have HD.  However, if the fetus did not have the disease causing genetic change identified in the family member, we would think the fetus had a very low chance to have HD. 

Bottom line, with our current technology, different families may have different levels of information available about the chances that a future child will have HD.  Genetic testing for HD in a pregnancy or during IVF will be possible for some families and for others it will not be possible.  Any family interested in pursuing testing must have an evaluation in a genetics clinic in order to find out if it is possible for their family and to discuss the benefits, limitations, and risks of testing in detail.  A genetics clinic will not push anyone toward testing, but will discuss the options.

Deciding whether or not one wishes to pursue genetic testing before or during a pregnancy is a very personal decision.  As with many reproductive decisions, genetic testing in a pregnancy can also be controversial.  It is a decision each couple must make for themselves and may be affected by many factors.  A genetics clinic should not only provide information about testing options and their utility, but support to help the couple make an informed decision about whether or not they wish to pursue testing. 

For more information about the genetics of HD, please visit the Johns Hopkins University Hirschsprung Disease Study website at http://chakravarti.igm.jhmi.edu/AravindaChakravartiLab/Hirschsprung_Study.html.

This article was especially writen for us by Courtney Nichols, MSc, ScM, CGC, Genetic Counselor/Study Coordinator, Johns Hopkins University, USA