Throughout their eight-year relationship, Allie LaForce and Joe Smith have dreamed of having a family. LaForce, a basketball reporter for TNT, wants four children, while her husband, a pitcher with the Houston Astros who started his career with the Mets, has a more practical approach: “Let’s start with one,” he tells The Post.

But the hope and enthusiasm around trying to become parents has been tempered by fear that Smith could pass on a devastating genetic illness to his offspring — and ultimately led LaForce and Smith on a mission to halt its spread.

The 34-year-old hurler is now watching his mother, Lee, battle Huntington’s disease, a complicated neurodegenerative disorder that affects patients’ movements, cognitive abilities and psychiatric state. It has sometimes been described as a mix of Alzheimer’s and Parkinson’s, and more than 30,000 people in the United States suffer from it. His maternal grandmother passed away from the disease in 2006.

Lee was diagnosed in 2012, and, two years ago, at age 59, she moved to a nursing home, where she needs help with daily tasks like tying her shoes and getting dressed.

“My mom can walk, but cognitively, it’s tough,” Smith explains. “They’re thinking my dad is going to retire and they’re going to see the grandkids or travel around and watch me play baseball, but it just doesn’t happen because it’s crippling [her]. I don’t even know how to explain it.”

Huntington’s is hereditary. That means Smith has a 50 percent chance of having the disease, which usually begins manifesting itself between the ages of 30 and 50. If he does have it, he’ll pass on those same odds to any children.

Family members can undergo predictive testing, but both Smith and his sister have opted to leave it to fate. “I’ve talked to people [who have tested positive,] and they’ve fallen into depression for months. I just don’t know how it would affect me mentally,” says Smith.

He doesn’t let himself become consumed with the scary what ifs, but not knowing can occasionally provoke anxiety: “If I drop something, it’s like, “What the heck? I used to catch that. Is it natural or Huntington’s disease?’ ”

However, the sports power couple isn’t gambling with the next generation.

Instead of conceiving naturally, they’re using in vitro fertilization in combination with genetic testing, allowing them to implant only healthy embryos without Huntington’s, a process they began in January. This will basically guarantee an HD-free child — thus eradicating the mutation for good in their future generations.

The technology is known as pre-implantation genetic diagnosis, or PGD-IVF, and it’s not uncommon for those at risk for carrying genetic disorders, such as cystic fibrosis and sickle cell anemia, to undergo the procedure.

There is currently no cure for Huntington’s, but Smith sees this as the next best thing.

“We have shifted our focus to IVF because I believe it is a cure. There’s nothing close right now that will take the HD gene out or get rid of it completely,” he says.

While PGD-IVF is a welcome medical advance to many families coping with hereditary diseases, the technique is not without ethical quandaries, with critics likening it to playing God.

LaForce and Smith, who are Christian, say the idea of controlling so many factors of conception felt a little “weird” at times, but there was no hesitation if it meant having an HD-free child.

“People can have their opinions. This is the best way for us to go,” says Smith. “Someone’s life work was working on IVF. That was their purpose on this earth and God created them.”

The couple — who are heavily involved in the HD community and constantly staying abreast of treatment breakthroughs — didn’t even know about this procedure until about two years ago.

“What’s so frustrating is that this is not presented to you as an option. It’s almost like you have to put this together yourself. Doctors have been genetically testing embryos for 13 to 15 years, and [they’ve been testing people for HD,] but they’re not always offered together,” says LaForce.

Dr. Erin Furr-Stimming, an associate professor in the Department of Neurology at the University of Texas Health Science Center at Houston-McGovern Medical School and director of the Huntington’s Disease Society of America Center of Excellence at UTHealth, agrees that the technique is underutilized for potential carriers of HD.

“There are multiple reasons [why] some haven’t been presented with this by their doctors — maybe they don’t know their family history or the cost is too high,” says Furr-Stimming.

‘Ultimately, research will cure this, but now we can put this money into action by helping families have HD-free kids.’

The procedure will not compromise Smith’s desire to stay in the dark about his own health.

“The neat thing about the PGD-IVF is you can actually go through the process without finding out your HD status,” says Furr-Stimming, who has advised the couple. “The hope is that even if he has the mutated gene, he’ll at least produce a number of embryos that are free of that mutation. The couple will never know whether or not there were embryos with the gene mutation.”

One of the biggest drawbacks to PGD-IVF is its exorbitant cost. Insurance covers very little of the procedure and its associated medications, and LaForce and Smith — who are working with doctors at the Houston Fertility Institute — will ultimately see a tab of between $35,000 and $40,000.

The couple hopes to make it more accessible to others. Since his mother’s diagnosis, Smith has devoted as much time to raising awareness and money for research as he has to his fastball.

“I get paid a stupid amount of money to play a kid’s game,” says Smith. “You’re always looking at ways to give back.”

Together, he and his wife of four years have brought in more than a million dollars for their foundation, HelpCureHD. They’re now using the money to help families defray the costs of PGD-IVF. Both the Cleveland Clinic and Houston Fertility Institute are on board, pledging discounts for couples referred to them by their charity.

“Ultimately, research will cure this, but now we can put this money into action by helping families have HD-free kids. It will be nice to bring people to our events and see healthy children and say, ‘This is where your money went,’ ” says Smith.

In the meantime, LaForce has begun the rigorous process of preparing her body for egg retrieval, all while crisscrossing the country to cover NBA games and host a new studio show, “The Bounce.” She’s been injecting herself, but last week she and Smith — who is recovering from surgery to repair a ruptured Achilles tendon — were finally in the same city, allowing him to give her the injections. “It made me smile knowing he contributed to it,” she says.

LaForce — who rose to prominence in the sports-broadcasting world as a sideline reporter during March Madness in 2014 — will have the embryos implanted during this year’s annual college hoops fest. And shortly after, she will know if she’s pregnant.

“We know it’s not a perfect science. I’m trying to be cautious and not overthink it,” she says.

And as they navigate this intense period, Lee Smith is always on their minds.

“Last week, Lee told me she’s worried about her grandkids having Huntington’s. She was getting emotional. She shouldn’t have it but there’s an element of guilt. I said, ‘I promise our children won’t have HD.’ I wanted to give her as much comfort as I could,” says LaForce, adding, “I told her that she has to hang on to meet her grandchild, who will be HD-free.”