All the baby books tell you to have sex when you’re ovulating. That’s the basis of conception. One sperm fertilizing one egg means you’re parents. Following that logic, it makes sense that if you’re not ovulating, you won’t get pregnant. That logic, however, fails to take into account the longevity of sperm and the sometimes fickle nature of a woman’s reproductive cycle.

It Takes Two

You need tow basic ingredients to get pregnant: an eager sperm and a waiting egg. Ovulation refers to the brief 12- to 24-hour window when your body releases that egg so it can meet up with that one lucky sperm. When you don’t ovulate, there’s no egg, so the sperm have nothing to fertilize. They eventually die off and get reabsorbed by your body.

Sperm’s Mighty Lifespan

The impressive lifespan of sperm is what makes is possible for you to get pregnant while you’re not ovulating. Sperm don’t get to your fallopian tubes right away, and they can swim around inside your body for up to six days. That means if you have sex today, while you’re not ovulating, then ovulate three days from now, you have all the necessary ingredients to make a baby. You must factor sperm’s lifespan into your conception or pregnancy prevention plans.

Understanding Ovaries

Your reproductive system is fragile and delicate. Changes to your diet, stress level, weight and numerous other environmental and emotional factors can completely reroute your menstrual cycle. The same is true of ovulation. Even if you have regular, 28-day menstrual cycles, ovulation can come at different times each month — or not come at all. You can ovulate from one ovary but not the other. Sometimes you can release more than one egg or release eggs from both ovaries. That’s why people who practice natural family planning often have as many as 10 days out of the month when they avoid unprotected intercourse, even if the woman isn’t ovulating all 10 of those days.

Pinpointing Ovulation

It’s not impossible to know when you ovulate. You can use the calender method, basal body temperature monitoring and cervical mucus patterns to determine when you’re fertile. You can also use test strips from your drug store that check for specific hormone levels during ovulation. The longer you monitor your fertility, the more familiar you’ll become with your own cycle and the more accurately you’ll be able to predict when you can have unprotected intercourse.

Interrupting the Dance

Hormonal birth control, such as the shot, the pill, the patch and the ring, suppresses ovulation. This means as long as you take these medications as they’re prescribed, you shouldn’t ovulate and you shouldn’t get pregnant. If you use your birth control inconsistently, especially certain types of pills, you could ovulate and become pregnant. That’s why no hormonal birth control method can claim 100 percent efficacy. If you use them inconsistently, use a condom or other backup method to prevent pregnancy until you get back on track.

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