Re: genetic testing
My hubby and I went thru it all. Being older parents, we felt we needed to know if there were potetial problems.
Before pregancy, we visited a genetic counsellor. They take a detailed family history of both potential parents and go back as many generations as possible. You tell them each and every health issue, each cause of death etc. They then give you a detailed report about the percentage of risk for disease, conditions, maladies, syndromes etc based on that history, the personal history of each partner and the ages of the partners. This can be done prior to marriage or at any other time.
During pregnancy, we had genetic testing done. There are two choices. CVS - Chorionic Villi Sampling - is done early, around week 10 of the pregnancy. They insert a sampling catheter thru the cervix and take a sample of the placenta. This is used to perform the genetic testing.
The same results can be obtained with the more popular Amniocentesis which is done around week 18. They insert a needle thru the abdomen to obtain a bit of amniotic fluid.
Each of these tests pose a small risk of complications, inluding miscarriage. The CVS test is a risk of about 2 percent for miscarriage and amnio is about 1 percent. BUT the skill of the doc performing either of the tests makes all the difference. The doc who did the CVS tests for me had a 100 percent success rate - not one miscarriage.
There are other tests that are far less reliable in determining specific genetic maladies. Around week 9, they can do an ultrasound and measure the "nuchal sac" - an egg-yolk like feature loated on the fetus's neck. If it measures larger than a certain size, there is a muh bigger chance that its down's syndrome. One of mine had a large-ish sac and I was told that it was like 70 percent likely to be down's. It wasnt.
There is another blood test done fairly early to check for certain downs syndrome markers. I forget the name of this and the exact time that its done. Thats because its hogwash to me. Each of my pregnancies came back as 80 percent or higher liklihood for downs and none of them actually were. I think this test causes nothing but worry.
When you marry a cousin, it has not been shown to increase liklihood of problems much at all. Unless there are certain conditions or diseases. And unless there has been alot of intermarriage within the family line. Thalessemia is one really nasty genetically inherited condition that needs to be on both sides and one that you should be aware of if its on both sides. It seems to be more prevalent in south asians.
If you have oncerns, a visit to a genetic counsellor will likely put your fears to rest.
Wishing you the best!