Endocrinology of Pregnancy - Experiencing Symptoms 1DPO

Starting pretty much right at 1DPO, I started having all these weird symptoms that can easily be related to early pregnancy. Granted, I don't know yet whether I'm pregnant or not -- will be finding out at 11DPo, on Sunday, at the earliest -- but I soon started an obsessive Google search to see if other women had pregnancy symptoms so early on.

Ends up that a lot of women have. This seemed both a little backwards and to make a lot of sense:

1. Backwards because, especially at 1DPO, the embryo hasn't implanted in the uterus, which causes the surge in hCG (the hormone that is detected in urine when you POAS).


2. To make a lot of sense because, I imagined, your body would "know" that "something" was up with your cycle this time around, something atypical.

Ends up that they're BOTH right. Sort of. After more research, I came across this textbook chapter regarding the endocrinology (a branch of biology and medicine dealing with, among other things, hormone secretion and reproduction) of pregnancy. The first point is obviously true, and was pointed out to readers of several forums, as hCG is detectable in urine in a very limited capacity after implantation and increasingly thereon out, with the average earliest ability to "read" these hormones through a HPT being 8DPO. The hormones are secreted as early as 6DPO, or at the time when the embryo is between 6 and 8 cells, but are not at high enough levels for detection until a couple days afterward.

The most interesting part of the chapter, though, was describing not the average implantation day, but what happens even at conception:

Pregnancy-related proteins can be found in maternal circulation shortly after conception. For example, a platelet activating (PAF)-like substance, produced by the fertilized ovum, is present almost immediately (1-4). After ovulation and fertilization, the embryo remains in the ampullary portion of the fallopian tube for up to 3 days. The developing conceptus travels toward the uterus, through the isthmic portion of the tube, for approximately 10 hours, and then enters the uterus as an embryo at the 2- to 8-cell stage (5, 6). With further development, between 3-6 days after conception, the embryo becomes a blastocyst floating unattached in the endometrial cavity (6). A schematic representation of the pre-implantation phase of pregnancy is shown in Figure 2. Before implantation, the blastocyst also secretes specific substances that enhance endometrial receptivity. Successful implantation requires precise synchronization between blastocyst development and endometrial maturation.

To date, little information exists regarding regulation of steroid production in the embryo. The early embryo and its surrounding cumulus cells secrete detectable estradiol and progesterone well before the time of implantation (8, 9). Mechanical removal of these cells results in the cessation of steroid secretion, while return of the removed cells through co-culture results in restoration of steroid secretion (8). Given this finding, steroid production by the conceptus is thought to be negligible by the time it has reached the endometrial cavity, since it is gradually denuded of cumulus cells as it travels through the fallopian tube.

(Emphasis mine.)

While the types and amounts of hormones given off by the fertilized egg may be negligible, to those who are sensitive to their bodies (implying the little changes, of course), they may start detecting changes as early as 1DPO or even at conception.

Of course, one must keep in mind that these same hormones, while in a slightly smaller amount, are also secreted whether or not conception actually occurred, so having symptoms that appear like pregnancy symptoms should be taken with a grain of salt. Not to say that these early signs of pregnancy aren't real (after all, I'm kind of betting on them being so! For obvious reason!), but that they are often identical to premenstrual and even simple post-ovulatory symptoms.

I sure hope it is, though. Because I can't imagine having all these stupid symptoms and nothing to show for it. ;)

Science is fun, ain't it!