Tarek and Christina El Moussa have been one of the most beloved couples on HGTV. Fans of Flip or Flop have watched them (cute kids in tow) take homes that are absolute wrecks and turn them into showcase properties anyone would love to buy.

Now, sadly, the co-hosts have announced they are separated. They haven't said what led to their breakup. And no one really knows all the factors that can lead to a split, except for the partners themselves. But the couple has talked publicly about their fertility struggles and Tarek's cancer diagnosis, which are both health issues that can take a serious toll on a relationship.

Health problems "can be extremely stressful," says Tara Fields, PhD, a marriage therapist in Marin County, California, and author of The Love Fix. (Fields hasn't met the couple.) "They can be opportunities to strengthen your relationship, or [they can] blow it apart."

In 2013, Tarek discovered he had thyroid cancer after a fan emailed Flip or Flop producers to point out a suspicious-looking lump on Tarek's neck. A biopsy revealed the cancer had spread to his lymph nodes. He then underwent radioactive iodine therapy, and had to be isolated from his wife and young daughter. "It was a nightmare," he said in a 2013 interview with People. "They stay in a different bedroom, and I can't stay with my daughter for more than a few minutes at a time."

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The family's health struggles didn't end there unfortunately. Because the couple knew they wanted to have a second child, Tarek had banked his sperm before his treatment, and Christina then went through two attempts at IVF—one of which ended in a miscarriage. After a third treatment worked, Christina worried throughout her high-risk pregnancy. She gave birth to a healthy baby boy in August 2015, but not before an unexpected back surgery laid up Tarek for weeks on end: "[His recovery] was two months of sheer torture," Christina told People

It's no wonder health crises can chip away at a relationship. They present a variety of challenges, says Fields, including psychological issues following a diagnosis, such as depression; and changing dynamics and roles as the couple navigates treatment. Indeed, research has shown a link between a decline in health and marital problems, especially in younger couples. 

So what can a couple do to make it through such a stressful time?

Remember that this can be a chance to grow closer, says Fields. If your partner is sick, support him or her by going to the doctor's visits. "If you're the one who is ill, allow your partner to take on new roles and care for you," she says. And when the dust settles, let your partner know that he or she is your hero, for all they have done for you.

What's more, both partners need to make sure they're in touch with their own feelings, Fields adds: Consider any unresolved issues an illness may dredge up. "Sometimes without you even knowing it, [a diagnosis] can trigger a lot of fears," Fields explains. “It’s important for couples to take that moment to honestly talk about their fears." 

"You either grow together, or you grow apart," she says.