One of the hardest trials a married couple can go through in life is having a sincere, burning desire to have children and being unable. Infertility has the potential to bring years of pain and sadness to a family. If you have friends struggling with infertility, be careful what you say, or you may add to their burden. Here are some casual comments that might seem innocent, but can emotionally kill your infertile friends.

"You don't know how lucky you are!"

If you ever say these words to a friend who is struggling with infertility, count yourself lucky not to have them thrown back in your face. When you're a parent, the lives of childless couples might seem easy and laid back, but when all they desperately want is to be parents themselves, this comment can be insensitive. Children are all they pray for, wish for, and hope for, and any lack of appreciation on your part for your kids will seem to them unfair and sad.

Put yourself in their shoes. Think of your life without your kids, and you'll realize how very empty life would be.

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"Pregnancy is no fun anyway."

Complaining about pregnancy is another dash of salt in the wound for couples trying everything in their power to get pregnant. Telling them they wouldn't enjoy the experience is like telling a man dying of thirst that water doesn't taste that great, anyway.

Sometimes, you'll communicate with infertile couples indirectly, like through Facebook or Twitter. Think before you post any comment complaining about pregnancy symptoms, weight gain, or the baby kicks that are keeping you up all night. Any woman desiring to have a child but is unable to would willingly go through nine straight months of morning sickness, gain 60 pounds, and lie awake sleepless for days on end if it meant she could bring home her own little baby at the end of it all.

"Just think of all the time you and your husband get to yourselves!"

It's true, not having kids frees you up to stay out later at night, go for spur-of-the-moment weekend trips, and you never have a meal interrupted or have to find a babysitter for date night. But a home can feel awfully lonely when you never have anyone else to share your lives with.

Holidays can be especially rough times for couples struggling with infertility. They have no one to hide Easter eggs for, no one to take trick-or-treating, and no reason to look forward to Santa's arrival on Christmas Eve. They might have nieces and nephews or friends' children who act as surrogates, but nothing can compare with the joy that comes from raising a child together, or the bond you share with your spouse when you bring a new life into the world.

"Aren't you glad you have more time for your career?"

Women especially might hear insensitive comments about how kids would take away from their career aspirations. This assumption stems from the idea that being a mother and having a career are mutually exclusive statuses, which isn't necessarily true. And some might assume that couples who can't have kids must have loads of money because they have two sources of income and no one to spend it on but themselves. Of course, none of these suppositions are always true.

For many women, having a career has not been their lifelong dream. Some women view motherhood as their ultimate goal; something they've prepared for their whole lives. When infertility rears its ugly head, the loss of this dream can be difficult to deal with. It's like telling a medical student at the end of her schooling that there are no jobs available for her, and never will be. A whole theoretical future has been wiped out, and she's left wondering what to do with her life now.

"Our pregnancies happened by accident."

None of us control our own fertility, so it's nothing to brag about if you happen to get pregnant more quickly and easily than your friends. Mentioning the ease of your baby's conception with a fellow mother or pregnant friend might sometimes be appropriate, but an infertile couple will only see the unfairness of the world and wish bitterly that pregnancy could come as easily to them. If you know a friend is trying to get pregnant, do not speak flippantly of your own fertility. The kindest response when someone confides in you about her difficulty getting pregnant is always commiseration and compassion.

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"You could always adopt."

Adoption is a wonderful option for many families and a great opportunity to change the life of a child. However, it isn't right for everyone. The expense alone is prohibitive, and there is no health insurance to cover it versus covering a pregnancy. According to AdoptionHelp.org, adopting a newborn costs between $10,000 and $30,000, depending on whether you use a non-profit agency or an attorney.

Besides the cost, there is nothing like conceiving and bringing a new life into the world that is uniquely a part of you and your spouse. Pregnancy bonds parents to a child long before he takes his first breath, and every mother dreams of being able to look into her child's face and seeing some characteristic of herself or her husband reflected there.

Do not assume because they've tried everything else, a couple will and should always turn to adoption at some point. It might not be right for them.

There are few words that can comfort a childless couple, but here are a few ideas for how to be there for them. The main thing to keep in mind is how you'd feel in their situation and never downplaying any emotional pain they might be feeling.