I call it 'guaranteed third-wheel syndrome'. This is a thing that happens to the single friends of newly married couples, particularly long-time friends of one of the partners. Prior to the marriage, these friends think of the newly acquired romantic interest as a neat, if likely short-lived, pet, and comfort themselves knowing that they've seen this before - they were here before, after all, and will likely be here long after. About the time that long-time friend is picking up a groomsman's tux or being fitted for a bridesmaid's dress, the syndrome begins to take effect. Yes, they heard you say how "this time it's different" but they'd heard that one before, only this time it would appear that things actually are different. By the time you've returned from your honeymoon and then proceeded to have as little contact with outside world as possible for the next 6 months, they've figured out that they will now be a permanent third-wheel whenever hanging out with you and have likely moved on to greener, more single-friendly pastures.
At that same 6 month time frame, you and your new spouse suddenly realize that you miss having contact with the outside world, that you miss having people around that you're not married to. Unfortunately, all your single friends have fled, but oddly enough, several other married couples have issued invitations to come over for dinner. Seeing no harm in meeting some new friends, particularly those who have experience with the greatest new thing in your live, and having no real alternative, you embark upon the perilous trail of.... The Couples' Date.
This isn't your double date from high school, Slappy. There will be no going to the movies our out to dinner - young married couples are poor. Pasta and conversation are on the menu for tonight, for one is cheap and the other is free, and if you're lucky, there will be a non-controversial board game. One game of the "Men are from Mars, Women are from Venus" board game will have you begging, with tears in your eyes, for Boggle, Bananagrams, or even Candyland.
Keep in mind, surviving these initial encounters is an art form. Eventually, these types of things can form profoundly strong bonds, strong enough that Steph and I routinely muse over the loss of our old couple friends back in Colorado. Initially though, survival is key. Do take note of the following:
1. If the couple you're visiting has a new baby, you will be expected to hold it. It's priceless, fragile, deeply loved, and it squirms, and they want you to hold it. God knows why. It's possible they believe you'll get the baby's scent in your nose and you too will come to the realization that your life will be forever incomplete without one. Perhaps it's just nice to have someone to pawn the kid off on while they try to remember what it felt like being free.
2. Regardless of the intent, there are some things to remember while holding that bundle of joy: If held long enough, it will either spew forth from one end or the other, or turn into a giant muscle and lunge for something that is not a toy, and typically dangerous. It's best to pass on that hot potato at the earliest possible opportunity, because yakked up formula stains and that sharp object sitting nearby is quite shiny and will attract the baby's attention sooner rather than later.
3. If your wife set this up, and it's quite likely she did (at least if you're me) it's likely that she'll have set it up with someone from work, and at some point she and the co-worker will begin talking shop and you'll be left with someone you've known for less than an hour to try to figure out something to talk about. Do your prep-work prior to this moment, find out something you can both comfortably discuss before your wife and his pair-off, and don't forget to thank me afterward.
4. It's perfectly fine to discuss the weather. It seems trite, but you're trying to survive, not solve the world's problems. Politics and religion can wait indefinitely. Work is always a solid topic, especially silly things about work.
Keep these in mind, and good luck.