I’m really sorry to hear of your loss. The form of Tay-Sachs that kids get is a terrible thing for parents and kids to have to go through.
Tay-Sachs is a single-gene disorder where both you and your partner have an abnormal gene for the disease and one normal gene. A child that gets one abnormal gene from each parent gets Tay-Sachs disease, a kid with one abnormal gene from one parent and a normal gene from the other is a Tay-Sachs carrier and will be normal, like you and your partner.
Unless anyone else in your family or your partner’s family had a kid with Tay-Sachs before (very rare) there is no way that most people would know this before you got pregnant with your first child. So it’s not your ‘fault’ that you had an affected child, but there are ways to do things differently in the next pregnancy.
Getting pregnant ‘the normal way’ there is a one out of four (25%) chance that your next child will also have Tay-Sachs. There are two choices – one is to go through In Vitro Fertilization with Preimplantation Genetic Diagnosis (IVF with PGD) where take eggs from your body after 8-10 days of fertility shots, fertilize them with your partner’s sperm, and test the embryos before putting embryos back inside your uterus – we want to pick embryos that are normal or Tay-Sachs carriers but NOT the ones with the disease.
The alternative is to get early testing when you are pregnant to see if the fetus has the disease – this is mostly for couples who would terminate the pregnancy if another child has the disease.
I recommend that you see both a genetic counselor, if you haven’t already, and a Fertility Specialist (Reproductive Endocrinologist / Infertility or REI MD) to talk about PGD, and not trying until you have seen both. A maternal-fetal medicine (MFM) MD can offer testing of the baby when you’re pregnant.
Rarely, some couples’ insurance will cover PGD testing if you have had a child with a genetic disorder and can get pregnant normally (so don’t have infertility) but want to avoid another affected child. Sometimes your MD needs to write a letter for you, and getting coverage can be a slow process.
If you go the PGD route, REI MD’s can work with different labs that do the actual genetic testing of embryos. I recommend a practice that works with Genesis Genetics, who are the most experienced lab in the USA for single-gene disorders. See the link below. I have no business interest in Genesis, but I know that you’re in good hands with Dr. Mark Hughes.