Ovulation: How to Spot Your Fertile Days When Trying to Get Pregnant

You have stopped contraception, and every month brings the same wait. People around you talk about “day 14”, apps and tests. Understanding ovulation means knowing when in your cycle a pregnancy is possible, so you do not miss your most fertile days.

Here is the cycle explained simply, the ways to spot your fertile days and how reliable each one really is, and the signs that it is time to see a doctor. No pressure: it often takes several months, and that is normal.

The menstrual cycle, explained simply

A cycle runs from the first day of your period to the day before your next one. It lasts 28 to 30 days on average, but any regular cycle of 21 to 35 days is normal, according to Quebec’s Mieux vivre guide and the NHS.

Somewhere in the middle comes ovulation, when an ovary releases an egg. The key point: it happens 10 to 16 days before your next period, the NHS explains, not on a fixed day after your cycle starts. With a 28-day cycle it falls around day 14, but around day 21 with a 35-day cycle.

Two lifespans explain the fertile window:

• the egg can only be fertilised for about 12 to 24 hours after it is released, according to the Mayo Clinic;
• sperm, on the other hand, survive several days in the female reproductive tract: 3 to 5 days according to the Mayo Clinic, up to 7 days according to the NHS.

The result: sex before ovulation is what counts most. Johns Hopkins defines the fertile window as the five days before ovulation, the day itself and the day after, roughly a week per cycle.

How do you calculate your ovulation?

The calendar method is the simplest. Note the first day of your period for several months (Johns Hopkins suggests six) to learn your usual cycle length. Then subtract 14 days: that gives your likely ovulation day.

These are only estimates. The Quebec guide, for example, puts the fertile days of a 28-day cycle at days 10 to 17, and the time between ovulation and your period can change from month to month, the Mayo Clinic notes. If your cycles are irregular, the calendar becomes unreliable, and it is better to watch your body’s signs.

The signs of ovulation

Cervical mucus. This is the most useful everyday sign. Just before ovulation, vaginal secretions become more abundant, clear, slippery and stretchy, “like raw egg white”, as the NHS and Johns Hopkins describe them. After ovulation they decrease and thicken. It can take a cycle or two to learn to recognise them.

Basal body temperature. Taken every morning on waking, before getting up, with an accurate thermometer, your temperature rises slightly at ovulation, by about 0.3 °C (0.5 °F) according to Johns Hopkins. An important limitation: this rise confirms that ovulation has happened; it does not predict it. It is mainly useful for learning your pattern over several cycles, at least three months.

Other clues, less consistent: a slight pain on one side of the lower abdomen mid-cycle, or premenstrual symptoms. Le Médecin du Québec lists these signs, along with regular cycles, among those of an ovulatory cycle.

Are ovulation tests reliable?

They are useful, but not foolproof. Sold in pharmacies, these urine tests detect the surge of LH, the hormone that triggers ovulation. When the test is positive, ovulation usually follows within 24 hours according to Johns Hopkins, or 24 to 36 hours according to Le Médecin du Québec: that day and the next are the most favourable.

The Mayo Clinic Health System acknowledges that these tests are not perfect: repeated false positives or negatives can happen, particularly with an ovulation disorder. Johns Hopkins considers them less reliable when cycles are irregular, for example with polycystic ovary syndrome (PCOS).

How can you boost your chances of getting pregnant?

First, by keeping your expectations realistic. The Quebec guide estimates that sex during the fertile window gives roughly a one in four chance of conception at 20, and one in twenty at 40. So it is normal not to be pregnant in the very first month.

Then, a few practical levers, according to the NHS and the WHO:

• regular sex, every 2 to 3 days, rather than only on your fertile days;
• a weight close to your healthy weight: being under- or overweight can make conception harder;
• no tobacco, alcohol or drugs, for you and your partner alike: the WHO lists smoking, excessive alcohol and obesity among the factors that affect male fertility;
• a review of any medication with your doctor, without stopping anything on your own.

For your partner, patience matters too: sperm take about two and a half months to develop, the INSPQ reminds us. A lifestyle change such as quitting smoking therefore takes several weeks, or even a few months, to show in the sperm.

Finally, folic acid (vitamin B9) should be started before conception: the NHS advises taking it before pregnancy and up to 12 weeks. The dose is set by your doctor or pharmacist. According to Canadian guidelines cited by Le Médecin du Québec, a higher dose, started two to three months before conception, is recommended with diabetes, epilepsy, significant obesity or a family history of birth defects. Our pointers are in eating well during pregnancy.

How long does it take to get pregnant?

Often several months. According to the NHS, for people aged 39 or under who have sex without contraception every 2 to 3 days, pregnancy will most likely happen within a year. The WHO defines infertility as no pregnancy after 12 months or more of regular unprotected sex, and estimates that about one in six people of reproductive age experience it during their lifetime.

The causes can lie with the woman or the man, the WHO points out: blocked tubes, endometriosis, PCOS, hormonal problems, but also ejaculation problems or poor sperm quality. A fertility work-up therefore always involves both partners.

Late periods and early symptoms should be read with caution: see when to take a pregnancy test and the first signs of pregnancy. Once the test is positive, our article on working out how many weeks pregnant you are will help you date the pregnancy.