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Carriers of Hemophilia

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or prenatal diagnosis. Women may choose these opꢀons for a number of different reasons. To discuss these opꢀons, contact your local hemophilia treatment center’s geneꢀc

counselor.

What if I would like addiꢀonal informaꢀon?

If you have any quesꢀons regarding this informaꢀon, would like addiꢀonal informaꢀon, or to pursue tesꢀng, you can contact your local hemophilia treatment center. They can put you in touch with a geneꢀc counselor at the hemophilia center or in your area. You can find a hemophilia treatment center near you at hꢂp://www.cdc.gov/ncbddd/hemophilia/ HTC.html. You can also find a geneꢀc counselor in your area by visiꢀng the Naꢀonal Society of Geneꢀc Counselors website at www.nsgc.org.

Pre-implantaꢀon Geneꢀc Diagnosis (PGD)

Carriers of
Hemophilia

» PGD is used to diagnose hemophilia prior to the embryo being implanted in the uterus. It involves in vitro

ferꢀlizaꢀon of embryos, followed by geneꢀc tesꢀng of the ferꢀlized embryos to determine which have hemophilia and which do not

» The embryos that are not affected by hemophilia will be

implanted

Where can I find more informaꢀon?

» The hemophilia mutaꢀon must be known in the family

prior to performing PGD

Please visit the following websites:

Canadian Hemophilia Society

» hꢂp://www.hemophilia.ca/en/bleeding-disorders/ carriers-of-hemophilia-a-and-b/

Chorionic Villus Sampling (CVS)

» CVS is performed during the first trimester, typically 10-
13 weeks into the pregnancy

Centers for Disease Control

Hemophilia Informaꢀon for Women
» hꢂp://www.cdc.gov/ncbddd/hemophilia/women.html

» CVS uses an ultrasound and catheter to obtain a sample

of the ꢀssue on the edge of the placenta (chorionic villi)

What you need to know

» This ꢀssue can then be tested for the family’s diseasecausing mutaꢀon
Naꢀonal Hemophilia Foundaꢀon

www.hemophilia .org
» hꢂp://www.hemaware.org/story/test-takers
» This is an invasive test; there is an approximate 0.5%
(1/200) to 1% (1/100) chance for miscarriage associated with the procedure
» hꢂp://www.hemaware.org/story/family-planning-carriers

» hꢂp://www.hemaware.org/story/knowledge-power- symptomaꢀc-carriers

Amniocentesis

» Amniocentesis is a procedure performed aſter 15 weeks

into the pregnancy

World Federaꢀon of Hemophilia
» hꢂp://www.wꢃ.org/
» It is performed using ultrasound and a long, thin needle to obtain a sample of the amnioꢀc ꢁuid surrounding the baby. Within this ꢁuid are cells from the fetus which can be tested for the family’s disease-causing mutaꢀon

» Amniocentesis is also an invasive procedure and, therefore, is associated with an approximate 1/300 (0.3%) chance for miscarriage

Indiana Hemophilia & Thrombosis Center

8326 Naab Road, Indianapolis, IN 46260
Tel: 317-871-0000 | Toll Free: 1-877-256-8837 | Fax: 317-871-0010 www.ihtc.org | hꢂp://www.facebook.com/IndianaHemophilia

©2017 Indiana Hemophilia & Thrombosis Center , Inc.
Rev 8/17

idenꢀfied, carrier tesꢀng is available to at-risk female relaꢀves by means of a DNA blood test. This is performed by looking for the presence or absence of the same mutaꢀon

Can a factor level tell me if I’m a carrier?

Inheritance of Hemophilia

What is hemophilia?

Father With Hemophilia & Mother Who is Not a Carrier

In the past, prior to the availability of geneꢀc tesꢀng, factor levels were used to determine carrier status. This method of determining carrier status is not reliable. For this reason,

factor levels in female hemophilia carriers should be

used only to determine the risk for experiencing bleeding symptoms, not to determine carrier status.
Hemophilia is an inherited bleeding disorder. People with hemophilia oſten bleed longer than other people. Bleeding can occur internally into joints and muscles, or externally, from cuts, dental procedures, or trauma. The two most common forms of hemophilia are hemophilia A, a deficiency of cloꢄng factor VIII, and hemophilia B, a deficiency of cloꢄng factor IX.

Parents

» If no male relaꢀve with hemophilia is available for tesꢀng, DNA blood tesꢀng can sꢀll be performed; however, it may not be able to detect all mutaꢀons

+

Father

with hemophilia

Mother

not a carrier for hemophilia

XY
XX

Limitaꢀons of Carrier Tesꢀng

Where does hemophilia come from?

» Deleꢀons (missing geneꢀc informaꢀon) or duplicaꢀons
(extra geneꢀc informaꢀon) in the factor VIII and IX genes are more difficult to detect in females if the mutaꢀon in the family is not known
The genes for both factor VIII and factor IX are located on the X chromosome (one of the two sex chromosomes in humans). Abnormaliꢀes (mutaꢀons) in the factor VIII gene cause hemophilia A, while mutaꢀons in the factor IX gene cause hemophilia B. Hemophilia varies in severity, depending upon the level of cloꢄng factor circulaꢀng in the blood. Males with severe hemophilia typically have less than 1% of normal factor acꢀvity, those with moderate have 1-5%, and those with mild hemophilia have 6-40%. Males with severe hemophilia are typically diagnosed before their first birthday while those with moderate/mild hemophilia may not be diagnosed unꢀl childhood or adolescence. There are also some individuals with mild hemophilia who are not diagnosed unꢀl adulthood. Currently there is no cure for hemophilia, but treatment is

available.

Hemophilia can occur in families both with and without a history of hemophilia. The majority of babies with hemophilia are born to women who are carriers. In some cases, these women do not have a family history of hemophilia and do not know that they are hemophilia carriers unꢀl their child is diagnosed.

  • Son
  • Daughter

carrier for hemophilia

  • Son
  • Daughter

carrier for hemophilia

  • without
  • without

  • hemophilia
  • hemophilia

» When carrier tesꢀng is performed with no previous detecꢀon of the factor VIII or IX gene mutaꢀon, a normal result in an at-risk individual does not rule out that she is

a carrier

  • XY
  • XX
  • XY
  • XX

Children

more oſten than females because females have an addiꢀonal X chromosome that acts as a “back-up.” Because males only have one X chromosome, any mutaꢀon in the factor VIII or IX gene will result in hemophilia. Females with a mutaꢀon on one X chromosome are called “carriers”.

Possible Carriers:

» A woman whose son is the first person in his family to be affected with hemophilia has an 80% chance of being a carrier. The only way to determine if she is a carrier is by performing geneꢀc carrier tesꢀng

Why is it important to know if I’m a carrier?

» Hemophilia carriers may be at risk for bleeding symptoms

» Carrier’s sons can have hemophilia and daughters can be

carriers with a chance for bleeding symptoms
» A woman whose mother is a hemophilia carrier has a
50% chance of being a carrier. The only way to determine if she is a carrier is by performing geneꢀc carrier tesꢀng
A female carrier has a 50% chance of passing on the gene

causing hemophilia to each of her children. Each son has a

50% chance of having hemophilia and each daughter has a 50% chance of being a carrier like her mother. A man with hemophilia will pass the gene on to none (0%) of his sons and all (100%) of his daughters. Therefore, his sons will not inherit hemophilia, but all of his daughters will be carriers.
» If desired, a carrier can learn if her fetus is affected with

hemophilia before birth

X-linked inheritance

» The chance for other female relaꢀves of an individual with hemophilia are based upon the specific family relaꢀonships and may be determined by a geneꢀc

counselor

Humans are born with 46 chromosomes, half from their mother and half from their father. Females have two “X” chromosomes (XX) and males have a single “X” and a single “Y” chromosome (XY). X-linked disorders are associated with mutaꢀons on the X-chromosome. These disorders affect males
» It is important to be aware of the recommendaꢀons for

pregnancy and delivery

Obstetric Recommendaꢀons

Do carriers of hemophilia have symptoms?

Obligate Carriers:

» To prevent bleeding in a newborn, there are specific recommendaꢀons for delivery of a male infant who has a chance of having hemophilia. This includes not using vacuum extracꢀon or forceps to deliver the baby. It is important to idenꢀfy if a woman is a carrier to know what precauꢀons, if any, should be taken at delivery
» A woman is called an obligate carrier if it is known that

she is a carrier of hemophilia based upon her family history

» About 30% of female carriers are at risk for bleeding problems due to having a low factor level. These women usually exhibit mild symptoms of hemophilia and may need treatment to prevent bleeding complicaꢀons or minimize symptoms

Inheritance of Hemophilia
“Carrier” Mother & Father Without Hemophilia

Parents

» A woman who has more than one affected son is an

obligate carrier

+

» In addiꢀon, for families with severe and moderate hemophilia, it is recommended that circumcision be delayed unꢀl it is determined if the baby has hemophilia. This tesꢀng can be performed by measuring the factor VIII or IX level from a sample of the umbilical cord blood

obtained at delivery
» Hemophilia carriers more commonly have heavy

menstrual periods, bruising, and nosebleeds. They may also bleed more during surgery, aſter an injury, or aſter

delivering a baby

» A woman who has an affected son and one or more affected relaꢀves in her family line (a brother or uncle, for example) is an obligate carrier.

Father

without hemophilia

Mother

carrier for hemophilia

  • XY
  • XX

» All daughters of men with hemophilia are obligate

carriers

» It is important to know that factor VIII levels can change in pregnancy, with oral contracepꢀve use, aerobic exercise, and chronic inꢁammaꢀon

How do I know if I’m a carrier?

Reproducꢀve Opꢀons

  • Son
  • Daughter

carrier for hemophilia

  • Son
  • Daughter

does not carry hemophilia gene

  • without
  • with

Carrier Tesꢀng

  • hemophilia
  • hemophilia

Women who have a chance to have a baby with hemophilia have mulꢀple reproducꢀve opꢀons, including natural concepꢀon, egg donaꢀon, or adopꢀon. Women may also choose to pursue tesꢀng using reproducꢀve technologies

  • XY
  • XX
  • XY
  • XX

» It is best to start geneꢀc tesꢀng in a male in the family with hemophilia to idenꢀfy the mutaꢀon in the factor VIII or IX gene causing hemophilia. If a mutaꢀon can be

Children

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