Ever since ninth-grade health class, you’ve been hearing about how easy it is to get pregnant. All it takes is one expired condom, one missed pill, one night with too many mojitos…until you actually want to get pregnant, at which point it might suddenly become the most difficult thing you’ve ever tried to do in your life.If you’ve been trying for more than a couple of months, you’ve probably mastered the delicate arts of tracking your cycle, timing intercourse, and surviving the gruelling two-week wait between peak ovulation and peeing on a stick. You may have been tested for polycystic ovarian syndrome endometriosis , and fallopian tube blockages, and your partner may have had his sperm analysed for abnormalities (assuming you're in a different-sex relationship — if you aren't, it's a whole other unreasonably challenging can of worms). And you’re likely getting just the tiniest bit crankier with each new birth announcement on Facebook.But the human body is infinitely complicated, and there’s more that goes into producing a healthy baby than we can possibly understand. Of course, there are the established fertility-slowers such as ageing, smoking, and certain STIs . But recently, scientists have discovered some new factors that may help explain, though the evidence is mixed, why some couples get pregnant more quickly and easily than others — and they’re not all what you’d expect.What you’ll read in these slides is probably pretty different than what Aunt Dot tells you at the family barbecue: You won’t find any advice to “quit worrying about it so much” or “just relax and stop trying.” (And while it’s clear that some lifestyle changes can have a big impact on subjects in scientific studies, remember that they’re no replacement for a diagnosis from a reproductive endocrinologist, particularly if you’ve been trying for a year or more.) Instead, you’ll find six unexpected factors that you may not have realised could influence your fertility…and what you can do about them now to up your chances of Instagramming a swelling belly soon.