Ovulation: Everything you need to know

Can you get pregnant on your period? And how do you know you're ovulating? We've rounded up the answers to the most common ovulation questions.
Ovulation graphic

Illustration: Nica Patricio

What exactly is ovulation?
Each month, one of your ovaries will release a mature egg, which will then travel down one of your Fallopian tubes. The lining of your uterus thickens in case the egg is fertilized. If it is fertilized, it travels down to the uterus and settles in the rich lining. The egg only survives for about 12 to 24 hours. If it isn’t fertilized, you shed that uterine lining (that is, you get your period).

What are my most fertile days?
Most women are most fertile in the five days before ovulation and on ovulation day itself (use this calculator to find out your most fertile days). While cycle lengths can vary, ovulation generally occurs 14 days prior to the onset of your next period. It’s hard to pinpoint exactly when the egg will be released, but because sperm can stick around for up to seven days after you have sex, your best bet for conceiving is to have regular sex from Day 11 to Day 16 (count the first day of your period as Day 1).

How can you tell if you are ovulating?
Some women claim they can feel it (like a backache or cramps on one side of the body). If you have really regular periods, you will be ovulating around the same time each month (give or take a day or two). But if you’ve just stopped oral contraceptives, if can take a few months to figure out your cycle. Some women rely on ovulation predictor kits (you can find them at the drugstore, near the pregnancy tests), look for changes in cervical mucus (it changes from dry to wetter and clearer when you’re about to ovulate) or chart their basal body temperature (BBT), which means taking their temperature orally when their bodies are at rest. Using a basal body thermometer (they’re more sensitive than regular ones), take a reading at the same time every morning before you get out of bed. A temperature that is slightly higher (anywhere from half a degree to 8/10 of a degree) indicates that you likely ovulated within the past 12 to 24 hours. After a few months of charting, you’ll get to know your body’s patterns better and be able to predict your most fertile windows—and the best days to have sex—with greater accuracy. There are also free online graphs and apps you can use to chart your temperature over time. Fun fact: Once you conceive, your body temperature remains elevated throughout the pregnancy.

Can you get pregnant during your period?
Yes. It isn’t likely, but it’s possible. Sperm can live in the Fallopian tubes for five or six days. If you have a short cycle (around 22 days instead of 28 days) or tend to have really long periods and have sex on the last day of your period, the sperm could survive until an egg is released during ovulation. It’s also important to note that some women could have breakthrough bleeding (also known as spotting) mid-cycle and mistakenly think it’s their period (spotting and ovulation can happen at the same time). Remember that if you’re off birth control after being on hormonal contraceptives for many years, it can take a while for your natural cycle to regulate and for you to get to know what’s typical for your body.

What are my chances of getting pregnant each month?
Conception statistics by month depend on the age at which a woman is trying to get pregnant. Conventionally, the younger you are, the higher your likelihood of conceiving each month. Even still, a woman who is 25 or younger only has about a 20 to 25 percent chance of conceiving with each cycle, and the statistics drop from there. By age 30, you’re looking at a 15 percent chance of conceiving monthly; by age 35, the stats are less than 10 percent.

Traditionally, women have been told that they should see a fertility doctor after 12 months of accurately timed, unprotected intercourse if they haven’t seen the second line appear yet. But Kim Garbedian, a fertility specialist at Hannam Fertility Centre in Toronto, says many fertility doctors believe that women should have a workup after trying for just six months. “Women over 35 years old or with risk factors for infertility—such as a history of endometriosis or sexually transmitted infections or a family history of early menopause—should definitely seek help after six months of trying,” she says. “I also believe that women with irregular cycles should see a fertility doctor for preconception counselling before even attempting to get pregnant.”

Ovulation kits: How do they work?
Ovulation predictor kits, or OPKs as they’re often referred to on trying-to-conceive forums and websites, are an easy way for women to track their potential ovulation dates. Standard kits work by detecting the luteinizing hormone (LH) surge in urine that comes with ovulation. Ovulation is expected to occur within 24 to 36 hours of the detected LH surge, so you should start testing in the days leading up to when you expect to be fertile to avoid missing the window. Advanced OPKs will also measure estrogen levels to help you determine peak times to have intercourse.

“Urine ovulation kits can be as accurate as blood work for detecting LH,” says Garbedian. “However, women with irregular cycles, such as women with polycystic ovary syndrome or poor ovarian reserve, or a high baseline level of LH may experience difficulty using them—they can potentially get false positive results.” For these women, LH level tracking, coupled with follicle monitoring by ultrasound, is more accurate at detecting ovulation.

Ovulation pain: Is it normal?
 “Ovulation pain, or ‘mittelschmerz,’ is unilateral mid-cycle pain that occurs around the time of ovulation,” explains Garbedian. (“Mittelschmerz” comes from the German words for “middle” and “pain.”) It’s fairly common, and it can be a dull ache or a sharp twinge that can last anywhere from just minutes to 24 hours. It’s usually mild and can be effectively treated with over-the-counter pain relievers, but some women are faced with a more intense degree of pain that may require a physician’s evaluation.

There’s no definitive answer as to why the pain occurs. Some believe that it’s the enlargement of the egg before release, while others hypothesize that the discomfort is related to the regular bleeding that a woman experiences in her ovary at ovulation.

If the pain is severe or increasing in severity, affecting daily activities or not responding well to over-the-counter medications, it should be investigated, says Garbedian. Try to keep a journal of your menstrual cycles, noting when the pain occurs—this information, coupled with an examination and other diagnostic tests, will help your doctor determine if something else is to blame for the tenderness. Seek medical attention immediately if the pain lasts longer than a day or is accompanied by fever, vomiting or pain while urinating.

What is the connection between ovulation and temperature?
Many women chart their basal body temperature in an effort to time intercourse properly each cycle—this means that a woman must take her temperature before rising each morning to detect tiny shifts in her body’s core thermal reading. A woman’s non-ovulating baseline temperature is between 36.2 and 36.5°C, but her BBT will dip below the baseline one day and spike above the next right around the time of ovulation. (Some women, however, may not get the dip at all. The temperature may increase slightly—about less than half a degree—when they ovulate. If you’ve had a slightly higher temperature for more than three days, you can assume that ovulation has occurred.)

The theory is that the egg is released around the time of the dip. “After ovulation, the corpus luteum releases a hormone called progesterone, which acts on the hypothalamus—the body’s thermostat—to increase body temperature,” says Garbedian. “But this type of monitoring really only helps women retrospectively confirm ovulation because the higher BBT readings after ovulation occur too late to be useful for timing sexual intercourse.”

The daily temperature readings will remain high until right before menstruation; if you conceive, the temperatures will stay on the high side long after the 14-day mark, when you should get your period.

How do you calculate your due date?
Everybody says that pregnancy is a long nine months, but it’s actually 40 weeks—which is more like 10 months! In general, it takes about 280 days to grow and gestate a baby, but it’s hard to know the exact day of conception (sperm can hang around in the reproductive system for a few days after you have sex). Plus, 40 weeks is only an average: Some babies wait 42 weeks before they make their big debut. Fun fact: The week of your last period and the week you ovulated are included in the 40 weeks, so if you go into labour on your due date, your baby is actually only 38 weeks old.

Many doctors use a method that sounds like a math test problem: Take the first day of your last menstrual period, add seven days and subtract three months. (For example, if you got your last period on March 1, you would add seven days to get March 8, then backtrack three months. February 8, January 8, December 8—this is your due date!)

Even if you think you know the exact night you conceived, some doctors prefer to date ultrasounds, which help them measure the gestational age of a fetus. Early in the first trimester, the technician may use a transvaginal wand if the uterus is deep in the pelvis or if the woman is overweight to get an image of the teeny-weeny baby (it looks more like a little blob or bean at this stage). Typically, the ultrasound is done over the stomach.

    Read more:
    How to get your body ready for pregnancy
    Best sex positions for getting pregnant
    15 signs you might be pregnant

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