Now don't get me wrong... I'm not one of those people who is obsessed with menstruation or thinks it's an enjoyable thing... I actually loathe it. Every month I've been proud of myself for not going on a tirade on Facebook about how much I hate having a period. The truth is, I'm miserable for 5 straight days during that "time of the month." However, as miserable as menstruation is, it's actually pretty freaking interesting. I've taken many lessons from this book, but there's one particularly interesting thing I want to share with you, especially if you've ever had a baby or if you are planning to have one in the future.
First, I need to do some explaining of how the menstrual cycle works so you understand why I think this is so interesting (and perhaps alarming).
Before you have a baby, you may think that pregnancy is "9 months long." We hear this everywhere from the time we are kids as it's in books, movies, on tv shows, from those around us, in jokes, etc. The funny thing about this is that when you are pregnant, you don't generally think in terms of months at all... you generally think in weeks. The reality is, pregnancy is more like 40 weeks long. In fact, the first "two weeks" of a pregnancy are the time before you've even ovulated, before egg and sperm have even met. That is, of course... if the length of your cycle before ovulation is two weeks... which is the beginning of the issue I wish to address in this blog entry, which is that of babies being "early" or "late" by a few weeks.
You see, another mainstream idea is that a woman's menstrual period is 28 days long, and they ovulate on day 14. This is true of some women. Actually, it's true for me. My cycle is exactly 28 days long and through charting my period for 2 years and through charting my basal body temperature, I can honestly say that my cycle is completely average. However, this is not the case for many women. This is why lots of women have tried to not get pregnant by only avoiding sex around the 14th day after their period, and lo and behold, they've gotten pregnant anyway. What's probably happening is that they don't actually ovulate when they are expecting they do, because their cycle is different than the typical 28 day cycle/day 14 ovulation theory. This doesn't mean they aren't healthy or normal, it just means they aren't average. The reality is a healthy cycle is generally 24 days to 36 days long. Some people say as long as you menstruate 10 times in a year, you shouldn't be concerned at all. If your cycle is shorter or longer, it may indicate some sort of problem, but then again, it may not... it may just be the way your body works.
The way your menstrual cycle works is there are two "phases," and these phases are divided by the day you ovulate. The first day of your period begins phase one, which is called the follicular phase. Once you ovulate, you enter the luteal phase. In most women, the luteal phase is almost always exactly the same length of time, give or take a day. The follicular phase, however, can vary. This is because things like stress or sickness can delay ovulation or make it happen earlier. My cycle is 28 days like clockwork, unless I am sick or going through a stressful time, when it can be between 24-28 days. Looking back at my charts over the last 2 years, it's interesting to see that months I got sick during the follicular phase were months where I had a 24 day period.
At any rate, where am I going with this rambling? Trust me, I have a point :)
When you take a pregnancy test and go to the doctor, most doctors base your "due date" on the date of your last menstrual period (LMP). They then calculate the first 2 weeks of your recent cycle as the first 2 weeks of your pregnancy, and the 2 weeks after that (the two weeks where you don't even know you are pregnant) are weeks 3 and 4. So by the time you've missed a period, you are already 4 weeks pregnant! But wait... if you don't have a regular cycle... are you MORE pregnant? No, you aren't more pregnant. But it could seem that way...
Here's an example:
When I was pregnant with my son, I had my last period on February 1st, 2009. I got pregnant with him on Valentine's Day-ish, and ovulated on the 15th. His due date was November 8th, based on LMP. Probably because my cycles are perfectly average, Aias was actually born on his due date, when my pregnancy was exactly 40 weeks 0 days.
Let's say that two other women also ovulated on February 15th that year, also only encountered sperm through whatever means on February 14th as well, but woman A had a 24 day cycle (perfectly normal) and woman B had a 36 day cycle (perfectly normal). Let's say all of us have a 14 day luteal period.
Woman A would have had her last menstrual period (LMP) on February 5th (ovulating on day 10 of her cycle). Woman B would have had her LMP on January 24th (ovulating on day 22 of her cycle).Let me be clear; this does not mean that any of us are further along than the other. If we all ovulated on the same day, and all had encountered sperm on the same day, our babies are at exactly the same stage of development. So why the different due dates? Simple: because of the 28 day cycle/ day 14 ovulation myth.
If you type these dates into a due date calculator, or by using only the LMP method or wheel that doctors use (which assumes a 28 day cycle, and a day 14 ovulation), we'd all have had different due date:
My due date: November 8th
Woman A's due date: November 12th
Woman B's due date: October 31st
The big question here though: WHY DOES THIS MATTER?
Here's why it matters: 2 weeks difference in pregnancy is a huge deal. It's a huge deal because every week of development in a singleton pregnancy between 0 and 40 holds value in terms of development. While people say babies are "term" at 37 weeks, a huge amount of development happens in those last three weeks.
Another reason why it matters is that doctors (and sometimes even midwives) start to get nervous if your baby is "late." Let's look at woman B, for example. Her baby won't be 40 weeks developed until November 8th. However, her "due date" is October 31st. Depending on the circumstances of her pregnancy, her care providers may want to push her to not go "beyond her due date" and maybe even want her to induce on October 31st so she doesn't go over her due date. Worse yet, what if they want to induce even earlier for whatever reason, and they are thinking they are inducing 2-3 weeks before the "due date" but are really inducing 4 weeks early. In pregnancy, weeks that your child is developing inside you are very valuable!
I've known dozens of women, literally, who were pushed by care providers to induce on their "due date" for "safety reasons" even though the women were really against it. Or women who were considered "a week late" and so they were pushed into induction. Some of these women were bullied into it with the threat of harming their babies, and then their babies were born smaller or with less developed lungs than their care providers thought. I can't help but wonder how many of these women were actually being encouraged to deliver before their babies were even ready to come out.
Keep in mind... these are only women whose cycles are considered within the normal range... so probably LOTS of women have cycles these lengths. What about women with even shorter, or even longer cycles? While shorter cycles are less likely, many women have super long cycles. For example, let's say a woman C has a 55 day cycle, and conceived under the same circumstances as myself, woman A, and woman B. Woman C's LMP would have been January 4th... so if you used the LMP method of determining a due date with this woman, you'd end up with a due date of October 11th!
Now, there are some measures in place that help with this. For example, woman C would probably be assumed to be further along, would be given a dating ultrasound, and they'd try to guess the "fetal age." If woman C had been keeping track of her period length or had a reasonable idea of when she had ovulated, this could be corrected and a proper fetal age could be estimated. If woman C was like me when she got pregnant, and wasn't keeping track of anything, she may have answered the "how long is your average cycle" question in the same way I did, by saying "I have no idea." While care providers could probably have come up with a reasonably accurate due date, it wouldn't be impossible to be off by a week or so. Especially because later in the pregnancy there's lots of opportunity for variation; with larger or smaller babies being considered further along or further behind at times (whether the ultrasound can actually determine how large a baby is remains another matter all together). You can see how tricky this can be. And Mommy Makes 3 points out, that with longer cycles like this, the LMP method is clearly a washout and it's actually better to use other methods.
Woman C would most definitely find herself in a position where her care providers would be trying to nail down her "actual" due date... but myself, woman A, and woman B have cycles that are "pretty regular" so care providers would most likely feel comfortable just going with the LMP method, even though the dates are so off, at least in terms of the developing baby.
So a few points i want to drive home:
- It's normal to not have a 28 day cycle where you ovulate on day 14.
- A week or two of development can be really important to your baby.
- The medical technology sometimes isn't there (or isn't offered) to really nail down your actual "due date."
- Due dates are often "best guesses" rather than set in stone.
- Your best bet, and maybe your baby's, is to track your cycles and use a care provider that doesn't brush you off and try to only use the LMP method of the "spinny wheel" when you tell them about the specifics of your cycle.
- Awareness of how your body works always offers you opportunities of empowerment, so learn as much about how your body works as possible.
Most of all... your baby may not really be early/late!
*** Extra special thanks to And Mommy Makes 3 for links provided, and for doing all my math! ***
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