One Friday night, when our toddler was finally asleep, my husband was giving me a tutorial on the fertility app he had been using to guide our natural family planning. He pointed out that it was the middle of my fertile window and, if I got pregnant, our baby would be born in August. We had been using the app to avoid pregnancy, but visions of backyard birthday parties danced in our heads. We decided to try—just for fun. I was surprised when my period failed to appear two weeks later, but it turns out we had picked the best time to get pregnant.
Your fertile window is generally defined as the six-day period that includes five days leading up to ovulation—when a mature egg is released from one of your ovaries and travels down one of your fallopian tubes—and the day after ovulation. This window is based on the understanding that sperm can survive for up to five days in a woman’s reproductive tract and an egg can be fertilized for 12 to 24 hours after it’s released. A study published in the New England Journal of Medicine found that nearly all pregnancies result from having sex in this period. And the likelihood of conceiving ranges from 10 percent five days before ovulation to 33 percent on the day of ovulation. Just 24 hours after ovulation, your chances of conceiving drop to zero. In other words, the window opens wider until it slams shut.
“Proper timing of intercourse is key to getting pregnant,” says Heather Shapiro, a fertility specialist at Mount Sinai Fertility in Toronto. “Not surprisingly, sometimes timing is an obstacle to fertility because people aren’t properly educated in recognizing the signs of ovulation. On the other hand, it’s one of the easiest problems to correct.”
To properly plan your baby-making schedule, you need to know when you’re ovulating. Regardless of the length of your cycle, ovulation usually occurs about 14 days before your next period. Physical signs, such as watery vaginal secretions, or pain on one side of your pelvis, can also tip you off that your egg is about to drop. “You can easily ballpark when to have sex by looking at the calendar,” says Shapiro. “And add to that your own body changes to confirm what you already know.”
Apps, such as the one my husband was using, are like Google Calendar for your ovaries. Their basic function is to flag when you’re expected to ovulate based on information you plug in from past periods. If your cycle is regular, apps are highly accurate. But, if you have irregular periods, the calculations can get more complicated and more likely to result in error.
Shapiro points out that it’s normal for your cycle to vary in length by up to eight days. This can make narrowing down when to have sex more challenging, which means you'll have to spend more time in the bedroom to maximize your chances. “Having sex a couple of times around ovulation, 48 hours apart, is probably sufficient,” Shapiro says. “And if you’re not sure when you’re ovulating, add an extra day.”
Another option is using an ovulation predictor kit that detects the surge of luteinizing hormone in your urine—a sign ovulation is imminent. Many women also track their basal body temperature, which involves taking your temperature first thing in the morning and being on high alert for a slight increase, which signals ovulation is about to occur. However, Shapiro cautions couples on using this approach because other factors, such as erratic sleep patterns and illness, can affect your temperature. Plus, it involves adding one more to-do to your morning routine. “Waking up every morning and, before even getting out of bed, remembering that you’re having trouble getting pregnant is very hard on people,” says Shapiro.
While having sex daily may be one of the most logical ways to increase your chances of getting pregnant, that too can be a big investment for a low rate of return. “I think it’s an unrealistic expectation for two people who have busy lives to be able to have sex every 24 hours for six days in a row,” Shapiro says. “And if you can’t meet your expectations, that creates a lot of stress.” Trying every day does offer a slight advantage, giving you a 37 percent chance of conceiving per cycle, but having sex every second day is almost as likely to result in pregnancy, at 33 percent, and is much more doable for most couples. Having sex just once a week brings your chance of getting pregnant down to 15 percent each cycle.
If you are up for a daily ritual of love-making, you can rest assured it won’t affect sperm counts: A retrospective study looking at nearly 9,500 semen samples found that daily ejaculation doesn’t impact swimmers or their ability to get the job done. However, the research shows that abstaining for more than 10 days can knock down sperm counts and your odds of conceiving. Still, Shapiro stresses that you need to do what’s comfortable for you and your partner, and take some time to get to know your intimate timetable.
“Trust yourself,” Shapiro says. “You’re probably getting the timing right. Don’t stress too much over it.” And don’t forget to have fun.