Your period is overdue and there are still no signs of it. Trembling with excitement you take the pregnancy test, holding your breath while you wait for the result. After a minute that feels like forever, you open your eyes and see … a single line. The test is negative. So why hasn’t your period started? And are you pregnant or not?
When your period is delayed, the most likely reason is that the day of your expected period is miscalculated. Even if you usually have perfectly regular cycles, you may suddenly have a cycle that is longer than normal. This is almost always because ovulation for some reason happened later than usual in that cycle.
The menstrual cycle has two phases: The follicular phase and the luteal phase. The follicular phase starts on the first day of your period, and ends the day you ovulate. The luteal phase starts the day after ovulation, and ends on the last day before your next period.
The length of the follicular phase may change from one cycle to the next. The length of the luteal phase, on the other hand, is typically stable. It varies from woman to woman, and any number of days between 12 and 16 is normal, but your individual luteal phase length will be the same in every cycle.
Let’s say your usual cycle length is 27 days, with ovulation on day 15 and a luteal phase of 12 days. The 28th day your period arrives, starting a new cycle. Then one month, ovulation doesn’t happen until day 19 of your cycle. The luteal phase will still be 12 days long as usual, which means this cycle will be 31 days instead of the usual 27. When your period doesn’t start on day 28, it’s therefore not really delayed – it is now not expected until day 32.
Read more: Understanding the menstrual cycle
Delayed ovulation is most often caused by some kind of stress, either positive or negative. Travels, exams, illnesses, exciting experiences or just coincidence may cause late ovulation and hence a “delayed” period.
If you are measuring your basal body temperature and know when you ovulated, and you also know the usual length of your luteal phase, you can easily calculate the day of your expected period. If you are using ovulation tests, you also have a good indication of your ovulation day, but remember that a positive ovulation test doesn’t guarantee that you actually ovulated. Ovulation may have happened later than you think, or not at all.
Can I be pregnant even if the test is negative?
Pregnancy tests turn positive when they detect the presence of the hormone hCG (human chorionic gonadotropin) in your urine. The secretion of hCG starts when the fertilized egg implants in your uterus between 6 and 12 days after ovulation. The first few days, however, there is too little hCG for the test to detect it. It is therefore possible to get a negative pregnancy test even if you are actually pregnant, if you are testing too early.
Most pregnant women will get a positive pregnancy test 12 days after ovulation, but if the egg doesn’t implant until 12 days after ovulation, it will obviously take a few more days before the tests turn positive. It is also possible to get a positive test earlier than 12 days after ovulation (sometimes as early as 8 or 9 days after ovulation), but you shouldn’t expect it. A negative test taken earlier than 12 days after ovulation should not be considered a reliable result.
Let’s use the same example as above. In a typical cycle, day 28 would correspond to the 12th day of the luteal phase, and you should get a positive pregnancy test if you had conceived. But because ovulation happened 4 days later than usual, day 28 is only 9 days after ovulation, and it’s probably too early to get a positive result. Perhaps you are pregnant, perhaps you are not. Wait a few more days, and take a new test if you still haven’t got your period.
You can read more about how and when to test in our article about pregnancy tests.
Corpus luteum cysts
If you know your ovulation day with certainty, and you have got neither your period nor a positive pregnancy test when your luteal phase should normally be over, you may have a corpus luteum cyst.
When you ovulate, a mature egg cell is released from the follicle (or follicular sac) and starts its journey though the fallopian tube towards the uterus. The ruptured follicle transforms into a secretory gland known as the the corpus luteum (“yellow body” in latin), hence the name luteal phase. The corpus luteum now begins to produce the hormone progesterone, which keeps the uterine lining intact and ready for a fertilized egg to implant. If conception doesn’t happen, the corpus luteum disintegrates, and progesterone levels drop until the uterine lining is no longer sustained. The lining is shed and you get your period.
Sometimes, however, the follicular sac reseals after having released the egg, and fluid accumulates inside it. This causes the corpus luteum to grow into a cyst, which keeps producing progesterone beyond the usual luteal phase length. This is called a corpus luteum cyst. These cysts are harmless and do usually not cause any other symptoms than the missed period, but if they grow big they may cause pelvic or abdominal pain. Corpus luteum cysts usually disappear by themselves after a few weeks.
A corpus luteum cyst will not prevent conception, nor will it usually affect the pregnancy. If you aren’t pregnant, however, it can be frustrating to wait for a new cycle and another chance of conception. If you suspect that you may have a corpus luteum cyst, contact your physician or your gyneacologist. In most cases, ultrasound will confirm the diagnosis. You may be asked to come back in three months to check that the cyst has disappeared.
If you are not quite sure when you ovulated, there is little else to do than wait for your period and take new tests every couple of days. If you are certain of your ovulation day, and your luteal phase has lasted more than two days longer than usual, you should contact your doctor to check if you have a corpus luteum cyst.