When did she ovulate?

January 1, 2009 9:28 AM

Maybe it's impossible to tell...but when did my girlfriend ovulate?

Her period was due December 4th, (she uses a popular website to track/predict). She didn't have it until December 10th. According to the site, her cycle varies from 26-32 days, with an average of 28.7. Had it started December 4th, she would have ovulated December 18th, however, according to the *actual* period, she ovulated on the 24th.

My question is, what determines ovulation? The actual physical start of a period? Or the *average*?

Could she have ovulated as early as 2 weeks after a 26 day cycle, since she has had those before?

We're having a really hard time dealing with what could possibly be pregnancy symptoms (or PMS), (nausea and tender breasts). Her period isn't due until the 5th, but if it doesn't come we will be testing.

*We had sex every day from the start of her period until 2 days after, but not since. She *said* she was on the pill, but has fessed up that she is not/has never been. We used no other form of birth control.

*This is not a question about should I DTMFA, merely what are your guesses on my chances of becoming a papa.

*[e-mail]

posted by anonymous to human relations (32 comments total)

Chances are apparently around 50% but there are calculators on the pregnancy sites that will tell you the typical time it takes to get pregnant based on both your ages. Its certainly not "slam dunk".
posted by zia at 9:48 AM on January 1

It's January 1rst, why not go get a pee stick and both of you can see if she's pregnant, than send her to a ob/gyn or planned parenthood.

FYI, I'm female and think it's pretty low to lie about birth control usage. It's one thing to mess up a day and miss a pill or have an oops moment with a condom breaking, quite another to do so intentionally lie about usage. I hope you both have options, are not pregnant and consider this a kick in the ass about your relationship.
posted by eatdonuts at 9:54 AM on January 1 [3 favorites]

*We had sex every day from the start of her period until 2 days after, but not since. She *said* she was on the pill, but has fessed up that she is not/has never been. We used no other form of birth control.

Any time you have unprotected sex with a girl, there's a chance you could get her pregnant. This timing calculation this is an imperfect science, especially when using an online planner and not a fertility specialist. You're hoping that this "rhythm" method of birth control is going to save your butt - but this, however, is the same type of birth control advocated by the Catholic church. And guess what? Even when practiced with consistency, it has a failure rate of 13% - 20% (Source).

To answer your question? Yes, she could be pregnant. You don't know EXACTLY when she ovulated.
posted by SNWidget at 9:55 AM on January 1

A woman can become pregnant even during her period. And no, you don't know when she ovulated.

(ps. you should probably get tested for stds. if she lied about something as important as birth control...well... better safe than sorry.)
posted by Green Eyed Monster at 10:03 AM on January 1 [6 favorites]

Ugh. I am trying to ignore the lie about being on the pill and actually answer your question. So I'll start with agreeing with Inspector Gadget and adding that her behavior is completely unacceptable. And you may want to get a complete STD screen since she has been untrustworthy so far.

There, I said it -- Okay, to your question. I have read everywhere that there is no true safe time to completely avoid pregnancy. So having sex during a period, while more unlikely to cause pregnancy, is not a valid form of birth control. Moreover, sperm can live in a woman's body for several days and "hang out" waiting for an egg.

I wish there was a definitive answer but if you are completely freaked out, you can take a home pregnancy test up to 4 days before a period is supposed to start. "First Response" home tests claim to be able to test this early and are known to be accurate. I would not count out pregnancy if it is negative today or tomorrow, but it may offer some minor peace of mind. They come in a 3 pack for 18 dollars and it may be worth it. If it was me, I would have her pee on a stick first thing in the morning tomorrow (when the hormone tested for its at its highest level of the day), and, if negative, try again a couple days later.

Good luck.
posted by murrey at 10:03 AM on January 1

These are basically high school biology questions.

My question is, what determines ovulation? The actual physical start of a period? Or the *average*?

No, it's the midluteal surge of luteinizing hormone and follicle stimulation hormone that determines ovulation. This may vary in the number of days from the end of the previous period based on probably dozens of factors: how heavy was the previous period, was it a normal period, how much stress has your girlfriend had in the last month?

Could she have ovulated as early as 2 weeks after a 26 day cycle, since she has had those before?
Yes, she could have.


*We had sex every day from the start of her period until 2 days after, but not since

"Vaginal bleeding" does not equal "period." The truth is that you really don't know for sure where she is in her hormonal cycle and therefore how fertile she really is. This is why the rhythm method sucks. Some women can tell you with some degree of certainty when they ovulate and their menstruation is extremely regular like clockwork, but that's certainly not true of all women and even in those cases, things happen unpredictably.

I agree that the way bigger issue is being lied to about birth control. Your partner isn't honest about something big like that, and now you are trying to determine whether she is pregnant based on what she tells you about nausea and tender breasts and when her last period was? There is a chance that she is pregnant and that chance is much greater than slim.

It's not clear from your question, but if you were having unprotected sex around the 10th of December and she's having nausea and breast tenderness, take the pregnancy test now. Take it again in two weeks.

And if you don't want a kid, take responsibility for birth control yourself.
posted by Slarty Bartfast at 10:08 AM on January 1 [1 favorite]

Ovulation is generally somewhere around day 14 of a 28-day cycle, as I recall. However, many women ovulate irregularly and she likely does if her period is irregular. Also, as murrey noted, sperm can live for days; and as others mentioned, you really don't know when someone is at peak fertility. There's a lot at play there.

One of the benefits of birth control is well-regulated periods (in most women). That she has irregular periods should have been your first clue that she may not be on the pill. That she tracks her cycle on a web site is also a flag. Perhaps she cannot take the pill - there are some health risks when associated with other factors in some women. Perhaps she just wanted to make you comfortable with having unprotected sex.

I would recommend, though, that she visit her OB/GYN. Not just for a pregnancy test, but for an overall checkup; and you might consider it as well if you both don't have documentation of a clean bill of health prior to engaging in unprotected sex. Unprotected sex is a big move and can carry life-long consequences. Yeah, it feels good but the pill doesn't prevent anything besides pregnancy (in 99.x% of cases). Is it worth risking your life, or a friendly long-term relationship with HPV or herpes, or our resurgent pal, syphilis?
posted by sadiehawkinstein at 10:13 AM on January 1

Home pregnancy tests are very inexpensive and incredibly accurate, now. The very best thing for both of you is to go to the drugstore and get the most accurate, easiest-to-read, soonest-indication test on the market. At maximum, this will run $20; average is $10.

To answer your question, though, there's no way to know when she ovulated nor even if she ovulated at all (it seems like her period may be irregular, and non-ovulation can be a symptom) without going to a doctor (or having a home pregnancy test state she's pregnant).

Just in case she doesn't feel she's in the window of optimum test accuracy (1-2 days after missed period, so that would be middle of next week), you guys can use the time while you wait to research other options and discuss your personal preferences so that when the facts are in hand, decisions can be made with a minimum of upheaval and terror.

Disappointingly bad form on her part to lie about something so integral to trusting intimacy. Please keep this in mind as why you should always wear a condom even when being told your partner is protected and disease-free, at least until you're both ready for the whole pregnancy + baby thing. Your peace of heart and mind will thank you for it, as you're probably realising now. This is an awful lesson via anxiety and implications, I know, and I hope you're able to find a calm core of compassion and decisiveness while you wait to find out the results.
posted by batmonkey at 10:14 AM on January 1

You can't track your cycle (accurately) with a website - you need to track your cycle by recording basal body temperature and other physical changes like cervical mucous and position. And evey then, it's an art, and not 100% effective.

Based on her previous cycle lengths, I would guess that she probably ovulated some time between December 22 and 28, although that's really just a guess, and timing can vary significantly for certain women. She certainly could have ovulated earlier.

She can take a pregnancy test today, but if she gets a negative she needs to retest up to a week after her period is due - false negatives are entirely possible this early on.

Also, this is a totally ridiculous situation, and I hope you know that. As a man, it is your responsibility to wear a condom unless you 1) completely trust your partner, 2) have both been tested for STDs, and 3) are prepared to deal with a possible accidental pregnancy.
posted by robinpME at 10:15 AM on January 1 [3 favorites]

Counting days alone absolutely DOESN'T WORK because every woman's body is different, and each individual woman's cycle can vary from month to month. If you want to practice birth control based on ovulation prediction, I strongly recommend reading Taking Charge of Your Fertility (website here: http://www.tcoyf.com/) which describes in detail the actual physical signs of ovulation, and how to use those to determine fertile times quite accurately.

(Of course, that being said, you'd have to rely on your partner for precision and honesty in tracking these symptoms...)

As for the timing you describe, if I'm understanding correctly it sounds like you had sex every day for the first 7 or so days of her cycle (day one always being the first day of the actual period, and I'm assuming about a 5 day period.) Some women do ovulate as early as day 7, however on average it's more like day 10-14 or so.
posted by eileen at 10:20 AM on January 1 [2 favorites]

My question is, what determines ovulation? The actual physical start of a period? Or the *average*?

The woman's body determines ovulation. It can happen any time. In fact, the only time of the cycle that's consistent is the length of time between ovulation and the period. When a non-pregnant woman has a late period, it's because ovulation decided to hold off for awhile. When a non-pregnant woman has a short cycle, it's because ovulation came as early as possible. Sometimes ovulation will seem to hold off till the woman's partner is back, if he's been away. Or it'll come after the woman has recovered from illness or stress. It's possible to chart the physical signs of ovulation as they are happening, but it's impossible to find out after the fact using only math.

Could she have ovulated as early as 2 weeks after a 26 day cycle, since she has had those before?

Yes, definitely.

I have a close friend who became pregnant from sex only on day 9 (if day 1 is the first day of the period), the one day in the whole cycle she had sex. That's 5 days of bleeding and then 4 days of not-bleeding.

If her period came on December 10, that day was day 1. Which days of that cycle did you have sex?
posted by xo at 10:22 AM on January 1 [2 favorites]

Even if you know exactly when she ovulated, there's no way to tell if she's pregnant without a test. If she's exhibiting symptoms, have her go pee on a stick. Most tests are sensitive enough that a mere four days isn't going to be too soon to register a positive result.

If you've had sex throughout her cycle and used no birth control, chances are quite good that she is indeed pregnant.
posted by grapefruitmoon at 10:36 AM on January 1

what are your guesses on my chances of becoming a papa

In general, women who are worried about pregnancy do not wait for x number of days into the future to decide to get tested. They go to the store and buy a test kit as soon as they can. You can buy them at the dollar store.

A woman who is worried about pregnancy doesn't fake her birth control.

Your girlfriend's actions indicate she's not all that worried, and if you aren't a papa this time, barring infertility or taking protective action on your own, you will be.
posted by sageleaf at 10:36 AM on January 1 [15 favorites]

I think the best you can do is that you probably didn't have sex during the optimal time for her to get pregnant, but that doesn't mean she couldn't have. Less likely to be pregnant than if you'd done it closer to when she probably ovulated, more likely to be pregnant than if you'd been using an actual mode of birth control.

Home pregnancy tests won't be as accurate today as they will be later, but they'll certainly be more accurate than assessing odds based on dates and periods. The EPT website says that about 30% of pregnant women will get a negative test this early. (Keep in mind that's not the same as a negative test having a 30% chance of being wrong. Those odds are presumably much lower. But even if they were that high, those are better odds than the non-odds you'd be able to get from the calendar).
posted by lampoil at 10:51 AM on January 1

If her period is only due in 4 days, it's worth it to have her take a pregnancy test. And have her take it with you there. I'm not saying you need to watch her actually pee on the stick or anything, just make sure you're there to look at it right after she takes it. If she lied about being on the pill, who knows what else she might lie about. If it's negative, she should take it again in two weeks or so (again with you present), like Slarty Bartfast said.

Also, breast tenderness and nausea could be pregnancy symptoms, but most women don't experience nausea until several weeks after conception (average is 5 1/2 weeks according to this website. It's more likely pre-menstrual symptoms, but IANAD, just someone who took a women's reproductive health class back in college.

She tracks her cycle online, has unprotected sex regularly, and lies about using birth control. She thinks enough about her cycle to actually track it, so ignorance on how babies are made is probably not the issue here. It sounds more like she is actually trying to get pregnant. She is certainly not trying not to.
posted by fructose at 10:54 AM on January 1 [4 favorites]

It's impossible to tell when your girlfriend ovulated.

It would be extremely difficult with several months of perfect information. Considering the girlfriend is not a trusted source of data, it's essentially impossible.

Good luck, OP.
posted by 26.2 at 11:28 AM on January 1

You're over thinking this. Having sex and lots of it while not on birth control is exactly how babies happen. You should assume that she's pregnant, get confirmation tests and then get paternity tests.

Remember, people who try to determine pregnancy via a women's cycle are called parents.
posted by Brandon Blatcher at 11:35 AM on January 1 [4 favorites]

[few comments removed - question is about ovulation not the girlfriend's behavior, thanks]
posted by jessamyn at 11:40 AM on January 1

And usually ovulation occurs right in the middle of two periods.
posted by kldickson at 11:47 AM on January 1

Some time ago New Scientist had an article on ovulation. Apparently, once ultrasound scanning became detailed enough that they could image the ovaries and egg production, the scientists running the study were startled to discover that there was no relationship between an egg being released into the fallopian tubes and a woman's period.

They discovered that egg production in the ovaries is on its own cycle; sometimes coinciding with the mensuration cycle, and other times not.

I found the whole study fascinating in a "ooh, human bodies are *neat*" kind of way.

Short answer: there's really no definite way to say (without an ultrasound examination) of when ovulation has occurred.
posted by Arthur Dent at 11:53 AM on January 1 [4 favorites]

I just want to reiterate that vaginal bleeding is not a reliable indicator that ovulation has occurred. There are lots of things (stress, obesity, excessive exercise, use of contraceptive hormones in the recent past) that can cause anovulation. When there is no synchronous pattern of cycling hormones and regular ovulation, vaginal breakthrough bleeding occurs erratically and can often just look like a "period" that came a few days earlier, was a little lighter or heavier or whatever. With irregular menstruation, you really have *no idea* when that next ovum is going to pop out.

Trying to figure out your risk through your partner's irregular menstruation pattern is not possible. You need to take a pregnancy test.
posted by Slarty Bartfast at 12:02 PM on January 1

Oh yeah, what Arthur Dent said.

Heh, Arthur Dent, Slarty Bartfast...
posted by Slarty Bartfast at 12:03 PM on January 1 [5 favorites]

I looked this up a few days ago and this page http://www.estronaut.com/a/ovulation_fertility.htm says you can tell the date of ovulation retrospectively from the start date of the next period. Subtract 14 days from the start of her period.
posted by Pigpen at 1:07 PM on January 1

And usually ovulation occurs right in the middle of two periods.

Sorry, but this is flat-out wrong. The length of a woman's cycle is NOT an accurate indicator of when she ovulated, and ovulation can frequently occur throughout a range of days in the menstrual cycle besides the exact halfway point between two periods. Ovulation depends (as mentioned upthread) on the interaction and timing of a woman's Follicle Stimulating Hormone and Lutenizing Hormone -- each on their own cycle of varying length.

In other words, five different women with 28-day cycles could routinely ovulate on five different days in that cycle. Woman 1 could ovulate on Day 10, Woman 2 could ovulate on Day 12, Woman 3 could ovulate on Day 14, Woman 4 could ovulate on Day 16, and Woman 5 could ovulate on Day 18 -- and they could all still begin their menstrual periods on Day 28, even though only one of them ovulated "right in the middle."

The only way, short of regular ultrasound tests, to get an idea of when ovulation happens (and to get a sense of the larger fertility window, since the fact that sperm can survive for several days means women are fertile for several days before ovulation actually occurs, as well as for the short time after) is either to regularly chart your cycles (the Fertility Awareness Method, also mentioned upthread) or to use a home ovulation test.

I have read everywhere that there is no true safe time to completely avoid pregnancy.

On one level, this isn't exactly wrong, but it's not factually correct. Women are both fertile AND infertile at different points during their cycles. For example, if a woman has definitely ovulated AND enough time has passed since ovulating that the unfertilized egg has passed from her body, it is physiologically impossible for her to get pregnant until her next fertile phase in her next cycle. (Of course, the amount of time until that next fertile phase can vary quite a bit -- it could be 12 days, it could be 3 weeks.) If you track your cycle, you can actually learn to determine what your fertile and unfertile phases are, but it takes some time, dedication, and discipline to do it.

In other words, for women who aren't tracking their cycles, it's the fact that they don't know when they're ovulating that makes it impossible to safely have unprotected sex, not that fertilization is a physiological possibility on every day of the menstrual cycle.
posted by scody at 1:07 PM on January 1 [4 favorites]

My understanding of how birth control works (as a woman who's been on it for ten years) is that ovulation doesn't happen when you're on it--so nthing that tracking her cycle on a website should have been your first clue that she was lying.

Hie thee to a Costco and buy pregnancy tests in bulk--if you stay with this girl, you're going to need them.
posted by peanut_mcgillicuty at 1:44 PM on January 1 [1 favorite]

Sorry, pigpen, but the page you link to contains misleading and even factually incorrect information.

For example, this...

The first day of a woman's period is 14 days after ovulation. The number of days between ovulation and the start of the next period is fairly consistent among all women.

...offers a potentially disastrous oversimplification of the luteal phase.

The luteal phase (the amount of time between ovulation and the beginning of the period) is NOT "fairly consistent" (i.e., 14 days) among all women. It is typically a broader range of about 12-16 days, but shorter and longer luteal phases (say 10 days, or 18 days) are definitely not unheard of. The fact that 14 happens to be the average number is totally, utterly, completely irrelevant for the purposes of looking at when any one individual woman might be fertile.

What IS consistent about the luteal phase is that for individual women, their own phase will be nearly constant from cycle to cycle. A woman with an 11-day luteal phase will always have an 11-day luteal phase (with only an occasional variation of about a day); a woman with a 17-day luteal phase will always have a 17-day luteal phase (again, with only an occasional exception). The average of 11 and 17 happens to be 14, but NEITHER of them are, in fact, ovulating 14 days before their periods start.

This is why women are fertile at very different points within their cycles, even when they have cycles of the exact same length. A woman who ovulates early and has a long luteal phase could potentially become pregnant during the last few days of her period, while a woman who ovulates later and has a short luteal phase couldn't potentially get pregnant until more than a week after her period ends.

If fertility were really a matter of such simple arithmetic as "a woman ovulates 14 days before her period," there would pretty much be no unplanned pregnancies.
posted by scody at 1:55 PM on January 1 [1 favorite]

You may find Pee On A Stick to be a helpful site in your pee-stick aquisition, which, clearly, is what you/she need! Good luck.
posted by leahwrenn at 1:57 PM on January 1

Sometimes sperm can survive inside a woman's body for several days; when attempting to get pregnant, I was told by a medical professional that 1-5 days was normal, but that even 8 days have been recorded.

About ovulation and the cycle, a personal anecdote: when attempting to get pregnant for the third time, I was peeing daily on test sticks to detect the ovulation. Even though I'd been quite regular (ovulation around day 16) before that, in the cycle which eventually lead to conception, my ovulation suddenly took place on day 8. Merely two days after my period had ended. Later, the ultrasound measurements of the foetus confirmed it.

(And yeah, that's one bit of TMI I'm certainly going to burden my kids with before they reach the age when they start getting ideas about "safe" days.)

I imagine the stress you must be going through, and the way your trust has been violated makes me wince. Nthing doing the test - pick a sensitive one, and repeat the test after a few days if it turns out negative but she doesn't get her period.
posted by sively at 3:36 PM on January 1

Above where Fructose said to watch her take the test?

"... some tests develop "positive" lines after the time limit. You should NOT read the test after the time limit (usually 10 minutes, but check the directions that came with the test.) Yes, this means you should throw the test away and NOT dig it out of the trash in three hours to see if a line magically appeared. And, if the "positive" line is gray or looks like a "dent" in the test, it is an evaporation line and not a true positive. " (from Pee on a Stick)

So, if you're not there, the test could be negative. but LOOK like it was positive if she shows it to you just a little while later.
posted by artychoke at 3:49 PM on January 1

Myself as an example: I am currently trying to get pregnant (yes, my husband is aware of this). I've been closely tracking my cycles for the past 6 months. I've been on fertility drugs for 2 cycles. My non-fertility drug cycles (6 cycles) were usually 28 days but could be anywhere from 24 - 32 days long, and ovulation that usually occurred on day 16 but could occur anywhere between day 11 and day 18. Sometimes I bled for 3 days, sometimes for up to 7 days. While I can almost always tell when I'm fertile (cervical fluid. ovulation pain) counting days is of little to no use for determining fertilility.
posted by echolalia67 at 6:00 PM on January 1

It's...hard to tell whether she ovulated. Going by a web site to track and predict doesn't work anywhere near as well as keeping track of certain biological signs she would be observing in herself -- you don't say whether she is into this enough to be recording her basal body temperature and mucus consistency, but...keeping track of things like that are a much more accurate way to track this kind of thing, more so than a calendar.

So it's impossible to tell whether she ovulated or not.

But you are close enough to when her period usually is that if you took a pregnancy test now, you'd be able to get some kind of a result -- and you may want to, because one thing that can delay a period is stress. Stress that you could get from worrying about being pregnant.

The only thing I can say about her lying about being on birth control is...there is one means of birth control that YOU can use, that doesn't rely on calendars or web sites or anything like that. It would also protect you each from passing any STDs on to each other, and it's also very cheap...something to consider, if she's reluctant to take on that responsibility herself.
posted by EmpressCallipygos at 6:29 PM on January 1

Just for the sake of saying... I've had sex without any form of birth control exactly once in my life. Pretty random timing really. That was February. My second son was born in November.

Looking at the statistics afterward it was pretty surprising to learn how unlikely that was. I know people who've "chanced it" many times with no pregnancy.

In a case like this you can try to figure out the odds as much as you like, but in the end odds and statistics don't apply on an individual level. Sure given the timing and the number of occasions and whatever else you can determine there might be a 67% chance or something, but in the end it's going to be 100% one way or the other, she is pregnant, or she's not. Nothing you can do now will affect that outcome.

And to echo others - lying about birth control is a pretty big worry and would certainly raise some very big questions for me.
posted by sycophant at 1:58 AM on January 3