I realized that I have whined about my 10 day luteal phase (or LP), and never really said anything about what a luteal phase is (in case any of you reading this don't know), and why it would be bad to have one only last 10 days. Well, here is all you need to know, and then some.
First of all, there are some basic things about the female reproductive cycle that everyone with a uterus really should know, but most people don't because, well, where would they learn these things? You'd actually be surprised at how little your doctor may know about these things as well. I got the bare minimum in sex ed, but I have two degrees in biology so I thought I was well-versed in female reproduction. Until I read a wonderful book called Taking Charge of Your Fertility by Toni Weschler I had absolutely no idea how little I knew. Fertilityfriend.com also has a good tutorial, but I will summarize. One huge basic thing that not everyone realizes: a 28-day cycle isn't the norm! I have 32ish day cycles. Some women have 24 day cycles. Another thing is that many women assume that they have 28 day cycles, because they have been on the pill for a long time. If you are on the pill, you will always have 28 day cycles, but those are annovulatory (no ovulation= no babies, which is how pills work to keep you from getting pregnant). This is not necessarily so. Whatever length your cycle is, make no assumptions about when you ovulate. Online ovulation predictors are absolutely not accurate, do not use them! Most women do not ovulate on cycle day 14. You may ovulate on CD 20 and have an 8 day LP, which is problematic. Maybe you ovulate on CD12 and have a 16 day LP. Alternately, you may ovulate on CD 10 of a 24 day cycle, and if you waited to CD28 to take a HPT (home pregnancy test) you would already be 4 days "late." If you have a 32 day cycle, ovulated at CD 20, and took a HPT at CD 28, it would be too early to really get a reliable result. Without charting (using FAM) or otherwise tracking ovulation, there is really no way to know when or even if you ovulated in a given cycle.
On to the science! A menstrual cycle has essentially two parts: the follicular phase (FP) and the LP, which I mentioned earlier, and they add up to any number of cycle lengths. Here is a basic breakdown.
This phase takes up the first part of your cycle, from the first day of red menstrual flow through the day you ovulate. Some women ovulate super early (like cycle day, or CD, 8) and some ovulate super late (anything after 25 days is generally considered late). During this phase, your uterus is chilling, making lining for a potential embryo to implant. Your ovaries are working on making your eggs mature so that they can be released at ovulation. Progesterone level is pretty much nil, and your estrogen is having it's own party. FAM (the Fertility Awareness Method) keeps track of this part of the cycle by having you take your temperature first thing every morning to establish a baseline, and also checking your cervical fluid and your cervical position. Yes, this does mean sticking your (clean) fingers in your vagina, get over it. It isn't any ickier than picking your nose, and honestly I think it's cleaner than that. Your basal body temperature (BBT) is at the lowest during this part of your cycle. During the early part of your FP, your cervix will be low in the vagina and firm to the touch, like your nose. Cervical fluid may be non-noticeable, or sticky, or lotiony. In the days leading up to ovulation your cervix moves higher up and becomes very soft (like your lips). Cervical fluid takes on watery or eggwhite characteristics. If you notice in the graph below there are two hormones that peak just before ovulation. These are Lutenizing Hormone (LH) and Follicle Stimulating Hormone (FSH). Their job is to spike 24-48 hours before ovulation, which tells your ovaries that they'd better get their butts in gear and spit out an egg (ovum), which is ovulation. This same spike also causes estrogen (or estrodiol) to cease and desist. Sometimes there is a slight temperature drop on the day of ovulation, but this is not a reliable indicator of impending ovulation. Anyway, once ovulation happens, we move on to the Luteal Phase!
Ovaries are made up of numerous follicles (hence, follicular phase) and each of these contains an ovum. Once the ovum is released, the follicle actually swells up and takes on a yellowish hue, and becomes a Corpus Luteum- a "Yellow Body", hence, Luteal Phase. This corpus luteum is very important to fertility. It produces progesterone, which is essential to sustaining an early pregnancy. Within 24 hours of ovulation, this progesterone spike causes your body temperature to increase by several tenths of a degree. This is how ovulation can be confirmed. By the time you can confirm ovulation based on temperatures, however, the fertile window has passed, so this is not an appropriate way to time conception sex. However, if you are trying to avoid conception, 3 days after ovulation is perfectly safe to have unprotected sex, because your little eggie has shriveled up and died. The progesterone that floods your system during the LP causes your cervical fluid (CF, or CM for cervical mucus) to dry up again, and your cervix will come back down and become more firm once more. Most of the time, the corpus luteum hangs out and does its thing long enough to create a 12-14 day LP. Variations within a day of this are perfectly normal, but if you get under 10 days for a LP, fertility issues arise. If there were sperm waiting for your happy little ovum, then there may be an embryo developing that is waiting to implant. Implantation happens about 7-10 days post ovulation, during which time your little embie is floating down your fallopian tube. If your LP is only 8 or 9 days, there is not sufficient time for the embryo to implant before your menstrual flow begins. The corpus luteum degrades at the end of your LP, which is evidenced by a plummet in BBT and the onslaught of AF (Aunt Flo, every womans *favorite* visitor) within 24 hours of the temperature drop, and you begin your next cycle. As an example of what a chart looks like, here is my prettiest one ever (click for a bigger view of it):
Ah, a normal fertile period, a 16 day LP, ovulation on CD 18...
I hope that made sense, I tried to keep it at about an introductory biology level, but please ask for clarification if something doesn't make sense!
Now, on to me personally. Since I have been having 10 day LPs, this presents a potential problem for when C and I are TTC (trying to conceive) in the not-super-distant future. We have plenty of time to address any issues, but we still need to address them. I did some googling around, and found out that there is a link between breastfeeding (the only info I found was from women still nursing their toddlers, just like me!) and cycles like mine: extended fertile periods, short LPs, like my chart from last cycle (I had to add the crosshairs manually because Fertility Friend wouldn't do it):
Prolactin, which is involved in milk production, can apparently interfere with the happy cycle depicted in the first graph above. If I had to guess, I would say that it causes the estrogen dropoff to be more gradual and therefore keep fertile CF around longer, and also causes the corpus luteum to be underdeveloped, generating less progesterone and degrading more quickly than in the absence of prolactin. That is my educated guess, I could very well be wrong.
My options are pretty much to wean J before TTC, which I planned to do anyway, but perhaps a couple cycles before TTC rather than the same cycle we planned to start TTC. I can also take vitamin B6 supplements before TTC to see if that makes a difference. If that doesn't work, I may be prescribed to take progesterone supplements. I strongly suspect that simply weaning J will solve my problem, since I had no issues whatsoever before having him.
I hope this was informative to anyone curious about FAM and/or how the female reproductive cycle works!