Understanding and Tracking Ovulation
Ovulation is the single most important event in your cycle. Getting the timing right - combined with good preconception habits - makes an enormous difference to your chances of conception.
What Happens During Ovulation
Ovulation is the release of a mature egg from one of your ovaries. It happens once per cycle - typically around Day 14 of a 28-day cycle - but the exact day varies significantly between women and between cycles. The released egg is viable for only 12-24 hours. Sperm can survive in the reproductive tract for up to 5 days, which is why sex in the days before ovulation is just as important as sex on the day itself. Use the Fertility Window Estimator to see your full 6-day fertile window based on your cycle length.
Menstrual phase
Days 1-5
Uterine lining sheds. FSH begins rising to stimulate follicle development in the ovaries. This is Day 1 of your cycle - the first day of true red bleeding.
Follicular phase
Days 6-13
A dominant follicle grows and matures. Oestrogen rises, thickening the uterine lining. Cervical mucus increases and becomes more fluid - a trackable sign you are approaching ovulation. See the signs section below.
Ovulation
Day 14 (avg)
LH (luteinising hormone) surges - this is what OPK strips detect. The follicle ruptures and releases the mature egg. This is the only time conception is possible. Begin timing intercourse now - see the timing section.
Luteal phase
Days 15-28
The empty follicle becomes the corpus luteum, producing progesterone. If fertilisation and implantation occur, hCG production begins and a pregnancy test will become positive from around 10-14 days after ovulation. If not, progesterone drops and menstruation begins.
Physical Signs of Ovulation
Learning to read your body's ovulation signals - combined with a tracking method like OPK strips or BBT - gives you a much more accurate picture than relying on a cycle app algorithm alone. The more signals you can read, the less you depend on any single one.
Cervical Mucus Changes
High reliabilityIn the days approaching ovulation, discharge becomes clearer, more slippery, and stretchy - often described as egg-white consistency. This is the body's way of helping sperm reach the egg. After ovulation, mucus becomes thick and cloudy again. Tracking this alongside OPK strips gives the most accurate timing.
LH Surge (OPK Strip)
High - predicts aheadA positive OPK strip means your LH has surged - ovulation typically follows within 24-48 hours. This is the most actionable real-time signal. See the full OPK usage guide below, and use the Ovulation Calculator to know which days to start testing.
Basal Body Temperature Rise
Moderate - confirms afterAfter ovulation, progesterone causes a sustained rise of 0.2-0.5°C in your resting temperature. You can only confirm ovulation occurred after the fact - but patterns over several cycles become predictive. Pair BBT with OPK strips so you have both a predictive and confirmatory signal.
Mittelschmerz (Ovulation Pain)
Low - unreliable aloneMild one-sided pelvic cramping or twinges around ovulation, caused by the follicle rupturing. Only 20-25% of women experience this consistently. If you do feel it, note the day and cross-reference with your OPK result - it can help calibrate your pattern over time.
Increased Libido
Low - supporting onlyMany women notice a distinct increase in sex drive around ovulation - thought to be an evolutionary mechanism. Useful as a soft signal alongside other methods. Combined with good intercourse timing strategy, this natural cue can be a helpful nudge.
Breast Tenderness
Low - supporting onlySome women experience light breast tenderness or fullness around ovulation, driven by the oestrogen and progesterone shift. More common as a luteal phase symptom. If breast tenderness is severe or unusual, mention it to your GP - it can occasionally signal a hormonal imbalance worth investigating before you conceive.
Ovulation Tracking Methods - Full Comparison
Tracking ovulation precisely can double your chance of timing intercourse correctly. For irregular cycles or if you have been trying for more than 6 months, tracking is especially important - and if tracking suggests ovulation is not occurring, that is a signal to see a specialist (see the irregular cycles section below). For women with regular cycles, LH strips combined with the Ovulation Calculator is the most effective starting point.
| Method | Timing | Accuracy | Cost (SG) | Best for |
|---|---|---|---|---|
| LH strips (OPK) | Predicts 24-48h ahead | High | $15-30/month (Watsons, Shopee) | Most women - easy, affordable, reliable |
| Digital OPK (Clearblue) | Predicts 2-4 days ahead (tracks E3G + LH) | Very High | $50-80/month | Those who want a clear digital result without line-reading |
| Fertility monitor (MIRA, Ava) | Predicts 4-6 days ahead | Very High | $300-600 device | Long-term trackers, irregular cycles |
| BBT charting | Confirms after ovulation | Moderate | ~$20 thermometer, free app | Pattern tracking over multiple cycles; pairs well with OPK |
| Cervical mucus | Up to 5 days ahead | Moderate | Free | Natural family planning, low-cost backup signal |
| Cycle app (algorithm) | Estimate only | Variable | Free to $20/yr | Regular cycles only; always supplement with OPK strips |
| Follicle tracking (ultrasound) | Same-day confirmation | Very High | $150-300/scan (private clinic) | Irregular cycles, fertility treatment cycles |
How to Use OPK Strips Correctly
OPK strips are the most practical way to detect your LH surge and time intercourse accurately. Used correctly, they predict ovulation 24-48 hours ahead - enough time to act. Pair your positive OPK result with the intercourse timing table on the fertility tips page to maximise your odds each cycle.
Start on the right day
For a 28-day cycle, begin testing on Day 10. For shorter cycles (24 days), start Day 7. For longer cycles (35 days), start Day 14. Formula: cycle length minus 17 = day to start testing. The Ovulation Calculator does this calculation automatically.
Test at the right time of day
Test between 10am and 8pm - not first thing in the morning (LH is produced in the morning but takes a few hours to appear in urine). Test at the same time each day for the most consistent results.
Reduce fluid intake beforehand
Do not drink large amounts of fluid in the 2 hours before testing - it dilutes the urine and can give a false negative. This applies to the pregnancy test strips too.
Read the result correctly
A positive OPK means the test line is as dark as or darker than the control line. A faint line is negative. This is different from a pregnancy test where any line at all counts as positive.
Act on the result immediately
Once you get a positive, have sex that day and the following day. See the timing table below for the full probability breakdown. You do not need to wait for ovulation to confirm - the LH surge means the egg is about to release. Improving sperm quality beforehand means the sperm waiting when the surge comes will be healthier.
Interpret no surge carefully
If you test daily and never get a positive, either you ovulated before testing started, you have a very short LH surge, or you did not ovulate that cycle (anovulation). See your GP if this happens consistently. Anovulation can be caused by PCOS, thyroid issues, stress, or low body weight - all covered in the irregular cycles section. If it persists, a referral to a fertility specialist may be appropriate - read about what comes next.
Irregular Cycles - Ovulation When It's Unpredictable
Irregular cycles (shorter than 21 days, longer than 35 days, or highly variable in length) make ovulation harder to predict and may signal that ovulation is not occurring reliably. The key causes in Singapore women are PCOS, thyroid conditions, high stress, and low body weight. If your cycles are irregular, the Ovulation Calculator results will be less reliable - combine it with daily OPK testing and BBT charting for a fuller picture. The fertility tips page covers lifestyle interventions (diet, inositol for PCOS, stress reduction) that can help regularise cycles.
PCOS (Polycystic Ovary Syndrome)
The most common cause of anovulation (no ovulation). LH levels may be chronically elevated, making OPK strips misleading - they may show false positives throughout the cycle. Cycles are often long and irregular. PCOS affects approximately 10-15% of Singapore women of reproductive age.
What to do: See a gynaecologist for confirmation. Tracking with BBT and cervical mucus alongside OPKs is more reliable than OPKs alone. Inositol (see the supplements guide) is the best-studied natural supplement for PCOS ovulation. Letrozole or Clomid may be prescribed by your OB-GYN to induce ovulation. If oral medications fail after 3-6 cycles, IVF may be discussed.
Thyroid Disorders
Both hypothyroidism and hyperthyroidism disrupt the HPO axis and can cause irregular or absent ovulation. Very common in Singapore women - thyroid conditions are often asymptomatic and go undetected for years before a TTC workup finds them.
What to do: A basic thyroid panel (TSH, T3, T4) is part of a standard preconception blood panel at most polyclinics. Ask for it to be included at your preconception check. Thyroid conditions are very treatable - medication typically restores normal ovulation within 1-3 months. See the Singapore fertility assessment guide for polyclinic costs.
High Stress / Low Body Weight
Hypothalamic amenorrhoea - where the brain suppresses ovulation due to energy deficit or psychological stress - causes missed periods and absent ovulation. Common in women with very low BMI, athletes in heavy training, or those under significant work stress.
What to do: Weight restoration and stress reduction are the primary interventions. No fertility drug works reliably if the underlying energy deficit is not addressed. The lifestyle section covers exercise moderation and stress management. A registered dietitian can help with energy-appropriate eating.
Perimenopause
Ovulation becomes less predictable in the years leading up to menopause, typically from the mid-40s. Cycles may be shorter, longer, or skipped entirely. Despite cycle irregularity, pregnancy remains possible, so contraception is still needed if not trying to conceive.
What to do: See a reproductive endocrinologist. AMH testing gives an indication of ovarian reserve. If ovarian reserve is very low, IVF with donor eggs may be the most realistic path. Read the IVF success rates by age for context.
Timing Intercourse for Conception
The fertile window spans the 5 days before ovulation and the day of ovulation itself - six days in total. The highest conception rates occur from sex 1-2 days before ovulation. Daily or every-other-day sex during the fertile window is optimal. The Fertility Window Estimator maps this out for your exact cycle. After ovulation, the window closes quickly - the egg is no longer viable by Day +2. This is why relying on a positive pregnancy test to confirm ovulation occurred is too late to act on for that cycle.
| Timing relative to ovulation | Approx. conception probability | Recommendation |
|---|---|---|
| 5 days before ovulation | ~5% | Begin trying - sperm will be waiting |
| 4 days before ovulation | ~10% | Continue |
| 3 days before ovulation | ~15% | Increasing odds |
| 2 days before ovulation | ~25-30% | High priority day |
| 1 day before ovulation | ~30-35% | Best day - Highest probability |
| Day of ovulation | ~20-25% | Still high - do not miss this day |
| 1 day after ovulation | ~5-8% | Egg is fading - much lower odds |
| 2+ days after ovulation | ~0-1% | Window is closed |
Data from Wilcox et al. (1995), N Engl J Med. Individual results vary.
Fertility Assessment in Singapore
If you have been tracking ovulation and timing intercourse correctly for 6-12 months without success, a fertility assessment is the logical next step. Singapore's public hospitals offer subsidised fertility investigations, and most start with a GP referral from your polyclinic. See the fertility tips Singapore section for cost estimates and first steps, or the full IVF guide if you have already been referred for assisted reproduction.
Polyclinic (any)
Subsidised (~$20-50)Preconception check
Blood panel, thyroid, rubella, STI screen, BMI check, folic acid prescription. The right first step before trying. Start here even before you begin tracking ovulation - some conditions are worth finding early. See the full preconception checklist.
KKH Women's Centre
Subsidised with referralGynaecology and fertility outpatient
Ovulation assessment, follicle scan, AMH, hormone panel, referral to IVF if needed. Singapore's highest-volume fertility centre. ART co-funding eligible.
NUH Reproductive Medicine
Subsidised with referralFertility evaluation
Full fertility workup for both partners, IUI, IVF. ART co-funding eligible. Good option for families in the west of Singapore.
Private gynaecologists (Raffles, TMC, ParkwayHealth)
$150-500 consultationDirect access, shorter wait times
Same services as public hospitals, no referral needed, faster appointments. Medisave claimable for certain procedures. Good option if you are over 35 and do not want to wait 4-8 weeks for a public specialist. See the IVF cost comparison for public vs private pricing.
Virtus Fertility Centre
Private pricing, some Medisave claimableFertility specialist
AMH, antral follicle count, sperm analysis, IVF. International group with strong clinical protocols. Multiple Singapore locations.
Ovulation Tools and Related Guides: