Why Your Period Isn't Late:

We see a lot of posts here that are some variant of the following:

"I am 4 days late. I took a pregnancy test but it was negative. I have symptoms. My breasts hurt and I've been feeling nauseous. What is going on?"

In order to explain the answer, I must first explain the biology.

The menstrual cycle is divided into two phases. The follicular phase and the luteal phase. During the follicular phase your ovary chooses a follicule to grow an egg. This follicule then spends the follicular phase growing fat and nourishing the growing egg. At ovulation this egg is released and the follicule that had previously housed it turns into the corpus luteum cyst and begins producing progesterone. As your levels of progesterone rise, you may experience "pregnancy symptoms." These are not always actually symptoms of pregnancy but are rather symptoms of progesterone, the hormone that is released both during early pregnancy and during the normal period after ovulation. Once ovulation occurs and your progesterone rises, the luteal phase begins. During the luteal phase, your uterine lining thickens in preparation for possible implantation and the egg makes its way towards the uterus, hoping to meet waiting sperm in the fallopian tubes. If conception does not occur your levels of progesterone will drop, causing your uterine lining to be shed and your period to arrive.

Why is this important?

Because- while the length of the follicular phase can vary greatly from woman to woman or even cycle to cycle. The length of the luteal phase hardly changes, if so by only a day or two.

What does this mean?

Let's use myself as an example. Prior to having my first child I ovulated around CD14. (The first day of your period (bright red and enough to need a pad or tampon, spotting does NOT count as a period) is considered CD1. Therefore CD14 is 14 days after the first day of your period). My luteal phase was always 11 days. This resulted in me having 25 day cycles.

14 day follicular phase + 11 day luteal phase = 25 day cycle.

"Okay, so if my cycles are always 25 days and I'm on day 28, am I late for my period?"

Not unless you know when you've ovulated. Because it is the date of OVULATION not the length of your cycle that determines whether your period is late.

Let's use me as an example again. Let's say one cycle, I ovulate CD20. This means my follicular phase is longer during this cycle, this is completely normal. However, this doesn't mean I'll have a 5 day luteal phase in order to have my regular 25 day cycle. Because if you ovulate LATE your period will come later as well. My luteal phase would remain 11 days. Giving me a 31 day cycle. This is still normal and my period would NOT be considered late.

20 day follicular phase + 11 day luteal phase = 31 day cycle.

Again, while the length between your period and ovulation (follicular phase) can vary greatly from woman to woman or even cycle to cycle, the length between ovulation and your next period (luteal phase) generally DOES NOT vary more than 1-2 days.

So how do you track ovulation?

Ultrasound is the only way to accurately pinpoint your exact date of ovulation. However, taking your basal body temperature daily and recording your cervical fluid findings can give you a highly accurate picture of when ovulation likely occurred and can confirm that it has indeed happened. If you want to get into charting your menstrual cycles, I highly recommend reading the book Taking Charge of Your Fertility by Toni Weschler.

"But I use OPKs."

OPKs are great at telling you when you MIGHT ovulate. But they alone cannot confirm that ovulation has actually occurred. It is possible have a LH surge (the hormone detected by OPKs) WITHOUT actually ovulating. Therefore, a positive OPK cannot be taken as confirmation that ovulation has occurred and therefore you cannot know whether or not your period is late. Unless used in conjunction with CM and BBT.

Conclusion:

Without ultrasound or without basal body temperature and cervical fluid findings you cannot accurately know whether or not and when you have ovulated (including if you use OPKs), and if you do not know when you ovulated, you cannot know if you are actually late for your period or not. Bodies are not robots. We are not machines. You may "always" have 28 day cycles, but it completely normal, healthy even, to experience an off cycle every once in while. Regular cycles can vary as much as a WEEK in length apart. Someone who experiences cycles varying from 25 to 32 days in length is still considered to have REGULAR cycles.

If you believe you are late for your period, but have not been able to confirm ovulation through ultrasound or bbt/cm and are getting negative pregnancy tests the cause is 1 of 3 things.

1. You've ovulated late, you are pregnant but it's too early to get a positive test.

2. You've ovulated late, you aren't pregnant and your period will arrive later than usual.

3. You haven't ovulated at all yet and may experience a breakthrough bleed (a bleed that follows a cycle in which ovulation occurs, a period can only be considered a period if you ovulated before it) OR you have not ovulated at all yet and may ovulate in the coming days/weeks.

Implantation can occur as early as 5-6dpo (days after ovulation). However, on average it occurs between 9-12dpo. This is why some women get a positive as early as 6-8dpo while it's more common to get a positive around 11-14dpo. Taking a test of the last day of your luteal phase gaurantees that you will get the most accurate result. However, if you don't know when you ovulated, you won't know when your period is due.

If you have been unable to confirm ovulation and are experiencing BFNs/negative tests. I recommend waiting one week before testing again.

There are a few caveats to this. If you are breastfeeding or have recently given birth, you may experience irregular or short luteal phases. This is due to the hormone prolactin (which encourages milk), as prolactin suppresses progesterone levels which causes short luteal phase. This is why some women have trouble conceiving while nursing.

As well, some supplements such as Vitamin B6 or progesterone supplements have been known to increase the length of your luteal phase.

I hope this helps. Feel free to ask questions below!