PMS or Pregnancy? What to Know About the Two-Week Wait

Any couple trying to conceive knows about the nerve-wracking "two-week wait"—the time between ovulation and finding out if you're pregnant. Can't stop wondering whether you'll get your period or a positive pregnancy test? Here's your guide to the difference between PMS symptoms and pregnancy symptoms, which helps you know what to expect during this stressful time.

It's a cruel reality that PMS and the early signs of pregnancy are nearly identical. The reason? You produce more progesterone the week after ovulation, whether or not you're pregnant. Progesterone is the hormone responsible for many PMS symptoms, like bloating, breast tenderness, and mood swings. 

If you're not pregnant, you'll stop releasing the hormone about 10 days after ovulation. (As levels wear off, your symptoms subside, the uterine lining sloughs off, and you get your period.) If you are pregnant, you'll continue producing progesterone (and experiencing PMS-like symptoms). "The difference between PMS and early pregnancy is very subtle," says Helen Kim, M.D., associate professor of Obstetrics/Gynecology and Director of the In Vitro Fertilization Program at the University of Chicago.

Implantation bleeding, which shows up in about 30 percent of pregnancies, happens when the fertilized egg attaches to the lining of your uterus. It usually starts around the time you expect your period (or a few days sooner), and can easily be mistaken for menstruation. It might also be accompanied by mild cramping that feels like pulling or tingling.

There are a few distinctions between implantation bleeding and menstruation though: "Implantation bleeding tends to be lighter and shorter in duration than a period," says Dr. Kim. "You may have spotting instead of full days of flow." It's also likely to be brown or pink, instead of red. But if you don't experience implantation bleeding, don't fret. You can still be pregnant and have a healthy pregnancy without it.

Although there's just a 15 to 25 percent chance of becoming pregnant each month (depending on your age), it's still important to act like you're pregnant until you know for sure. Avoid alcohol, limit yourself to one to two cups of coffee per day, skip fish high in mercury, and avoid raw or undercooked seafood, meat, poultry, and eggs. "Don't make yourself crazy about restrictions, but treat yourself as if you're pregnant—you could be," says Dr. Kim.

You should've also started popping a prenatal vitamin that contains 400 to 800 micrograms of folic acid before the two-week wait. Folic acid helps prevent neural tube defects, and your baby's neural tube—which becomes Baby's brain and spinal cord—develops during the first 4 weeks of pregnancy. If you haven't started taking these vitamins yet, it's a good idea to start now. 

Finally, you should also be mindful of physical fitness, no matter your two-week wait symptoms. "If you normally engage in moderate-intensity physical activity, keep it up," says Dr. Kim. Exercise is a great way to relieve stress, and stress affects fertility, she says. Still, Dr. Kim warns that this isn't the best time to adopt a new or intense training program, which can put too much stress on your nervous system. Activities that significantly raise your core body temperature, such as hot yoga or heated spinning, could affect implantation.

If you get your period less than 14 days after you ovulate, it could be a red flag that something is affecting your ability to become pregnant. It could be as minor as miscalculating ovulation, or it could be a condition called luteal phase defect. "This means your body isn't producing adequate levels of progesterone to maintain a pregnancy," says Dr. Kim. Your doctor may prescribe extra progesterone following ovulation to help lengthen your luteal phase.