You hold a stick in your hands, one that you’ve just peed on. It foretells a future of sorts, for you. But the magic behind that stick is really all about a biochemical sandwich and a scientific test named ELISA. By Jeanne Garbarino, DXS Editor OH MY GOD OH MY GOD OH MY GOD OH MY GOD OH MY GOD OH MY GOD
Over and over again, that was all I could say. At the same time, I heard my husband on the other side of the bathroom door, in a very panicked voice asking, “Why are you saying oh my god? WHAY ARE YOU SAYING OH MY GOD?!?!”
Though, he really knew why.
The events immediately preceding our synchronous freak out session involved unwrapping a small plastic wand, removing its lilac cap, and subsequently inserting its absorbent tip into my stream of pee. Yes, folks, we are talking about the wand of destiny that is the pregnancy test.
Shortly after that lucky sperm cell unites with the prized product of the ovulatory process, theegg, a woman will immediately begin to experience changes required for growing another human inside of her body. One of the first detectable signs of pregnancy is a surge in a hormone called human chorionic gonadotropin or hCG.
Once the fertilized egg finds a cozy resting place in the wall of the uterus (a process termed implantation), the production of hCG is significantly ramped up. On average, implantation usually takes about 8-10 days for normal, healthy pregnancies. It is around this point on the baby growing timeline that home pregnancy tests can begin to detect the increased presence of hCG.
Chronologically speaking, we have sex, a sperm cell fertilizes an egg cell, said fertilized egg implants into uterus, our bodies up the production of hCG, and we pee on a stick to find out if all of these things really happened. But, exactly how do these little wands of destiny work?
The technology harnessed within the pregnancy test involves a biochemical assay called a “Sandwich ELISA” (ELISA= enzyme-linked immunoabsorbant assay, more on the “sandwich” part in a bit). The general function of an ELISA is to detect (and sometimes quantify) the presence of a substance in a liquid. In the case of a home pregnancy test, the substance is hCG and the liquid part is our urine.
Once pee is applied to the pregnancy test, it travels along the absorbent fibers, reaching defined areas that are coated with molecules, called “capture” antibodies, specifically designed to capture hCG. To help you visualize antibody science, picture a lacrosse stick, except the mesh pocket can only fit one specific type of ball:
Now, back to the sandwich part. On a home pregnancy test, there are three separate zones containing capture antibodies. Using their sharp wit and radical humor, scientists came up with “sandwich” to describe this sort of ELISA as they felt it was analogous to two slices of bread surrounding some delicious filling. Hilarious, right?
Ok, now that you’ve calmed down from laughing so hard, let us get back to the science. The first “slice of bread” is called the reaction zone, the “sandwich filling” is called the test zone, and the “last slice of bread” is called the control zone (see figure 2). Each of these zones is coated with capture antibodies, but differ from each other in how they work.
The antibodies on the reaction zone will capture only hCG and will detach from the strip upon exposure to urine. The test zone also contains capture antibodies that can only bind hCG, except they are securely attached to the absorbent strip, plus, there is an added dye. The control zone contains a general antibody (a lacrosse stick that will fit any ball) plus a dye, and serves to let the frantic user know that the test is functional.
As urine travels up the absorbent strip, it takes with it the reaction zone antibodies. If the urine is obtained from a pregnant woman, the reaction zone antibodies will be bound to hCG molecules found in the pee. When the pee solution reaches the test zone, there are two possible outcomes. If you are pregnant, the hCG/reaction zone antibody complexes will stick to the test zone antibodies and cause the dye to release (sometimes in a little “+” formation). If you are not pregnant, the reaction zone antibodies will just pass on through without saying hello.
The test culminates at the control zone, which is lined with general capture antibodies. Going back to picturing antibodies as lacrosse sticks, you will see that only the shape and size of the mesh pocket varies; the stick part is always the same. The general capture antibodies on the control zone will recognize and bind to the “stick” part of the reaction zone antibodies, and release a dye while doing so. This is how we know that the test worked correctly.
Biochemically speaking, the home pregnancy test is nothing but a soggy antibody sandwich that smells of urine. From a family planning standpoint, however, this technology can impact us in ways beyond belief. But, aside from the potential for the “are you pregnant” window to induce one into a hyperventilated state, the process happening within that handheld chemistry lab is actually quite impressive. In a matter of minutes, we can know if it is ok to go out and party with friends, or if it would be a better choice to stay in and begin to nest – all from the comfort of our own bathrooms. Three cheers for science!
For a cool animation showing how a pregnancy test works, go here. Visit WomensHealth.govfor more information about pregnancy tests. Planned Parenthoodoffers scientifically accurate information about women’s reproductive health. For blogs, check out this list on Babble, and this list on BlogHer.
Wilcox AJ, Baird DD, Weinberg CR. Time of implantation of the conceptus and loss of pregnancy. N Engl J Med. (1999) Jun 10;340(23):1796-9.
Jeanne, would you like some…peeeaaasss? License information here.
I was seven weeks deep when it hit me. Suddenly, I was in a chronic state of queasiness. Under most circumstances, I had it under control. Sure, I would gag every time I brushed my teeth, but (mostly) I could keep it all down. Then I went to my aunt Diane’s house for dinner.
Aunt Diane rolls with a crowd of self-made Italian chefs and, as a result, most of her cooking falls under the “rustic Italian” umbrella. It is not uncommon to see sitting in her cupboard a massive inventory of jarred plum tomatoes or for an entire section of her freezer to be dedicated to homemade vodka sauce, always frozen in those takeaway containers that originally brought us egg drop soup. Under normal circumstances, I’d be psyched to eat over.
I don’t recall the entire menu, but there is one side dish that has been forever burned into memory, and not in a good way. I remember starring at my plate, specifically at the heaping pile of sautéed peas. I kept rearranging the peas on my plate, sometimes spreading them out, sometimes piling them up. Then Diane looked at me and excitedly asked, “Jeanne, did you try my peas? I made them just for you!” I don’t know what compelled her to make these peas for me. Perhaps it was because I am a vegetarian and the rest of the meal involved meat? But, there they were, staring me down, and there Diane was, watching with anticipation, waiting for my approval.
Because I adore my aunt Diane and I wanted to make her happy (after all, she did just cook an entire meal for my small family), I scooped up a moderate amount of peas with my fork and deposited them in my mouth. I had to use every fiber of my being to chew them, and even more effort to actually swallow. My body was not cooperating and I had to implement a state of near meditation to keep them from coming back up. Luckily, I kept my cool and was able coerce my face into showing a smile while simultaneously telling my aunt and friend that her peas were delicious.
Credit: Jeanne Garbarino.
My husband picked up on my soaring level of discomfort and without missing a beat, ate all my peas when Diane wasn’t looking. We ended the evening with my stomach contents intact, but barely.
The next morning, as I was preparing my 18 month-old daughter’s daycare lunch, I remembered that we were provided with a parting gift of sautéed peas. I took them out of the fridge and proceeded to aliquot them into containers more suitable for a toddler. As I removed the lid, the onion-tinged aroma of Diane’s sautéed spring peas smacked me across my face. My body was clearly angry about what I had done to it the night before and, as if it were in a state of protest, I found myself sprinting to the bathroom where I began to puke.
From that day forth, I could not eat peas, let alone see or smell them, without eliciting extreme nausea. It didn’t matter what time of day, the mere presence of peas, although not necessary, was sufficient to make me toss my, well, peas.
It has long been known that nausea and vomiting are common symptoms of pregnancy. In fact, documentation of this phenomenon goes as far back as 2000 BC. However, the term “morning sickness” is a complete misnomer. For one, pregnancy-related nausea and vomiting is not just a morning thing. It can happen at any time of day. Second, the term “sickness” suggests a state of unhealthiness. We know that perfectly healthy pregnant women who deliver perfectly healthy babies experience morning sickness, and this type of nausea and vomiting is not an indicator of maternal and/or fetal health.
But, that doesn’t change the fact that it sucks.
Morning sickness, more appropriately known as nausea and vomiting in pregnancy (NVP), affects approximately two-thirds of women in their first trimester of pregnancy. In many cases, morning sickness subsides at the end of the first trimester. In other cases, the symptoms of morning sickness can last for the entire pregnancy. For both my pregnancies, I experienced morning sickness for the first 5 months.
I feel so lucky.
No one really knows the exact mechanisms responsible for the onset morning sickness. We do know that the drastic hormonal changes that occur during early pregnancy certainly play a role; however, these effects are likely indirect. For instance, estrogen levels do not differ between pregnant women with morning sickness and those who do not experience symptoms. Furthermore, there is no causal relationship between human chorionic gonadotropin (hCG), the early pregnancy hormone detected by pregnancy tests, and morning sickness, despite the fact that peak hCG levels and peak severity of pregnancy-related nausea and vomiting occur at approximately the same time.
Based on these observations, scientists suggest that the hormonal fluctuations in pregnant women can elicit different responses in an individual, rendering some extremely susceptible and others remarkably resistant to the same stimulus (with regard to nausea and vomiting). This begs the question: Is there a genetic predisposition to morning sickness?
While a “morning sickness” gene has not been identified, a few lines of evidence point toward a potential for inheriting the tendency. For instance, identical twins, are fairly likely to share a tendency to morning sickness. Also, you are more likely to experience morning sickness if your mom experienced it, too. Even though genetics may be involved, the onset of morning sickness is probably what scientists call “multifactorial,” a result of a very complex interaction between genetics and environment, making it difficult to find a treatment that is effective and safe for everyone.
Until more is known, we are stuck eating saltines and sour candy. At least it’s something, right?
Food aversions and morning sickness
Make them if you dare. Credit: Jeanne Garbarino.
For my first pregnancy, it was smoked salmon, which I probably shouldn’t have been eating in the first place. For my second pregnancy, it was peas. (Interestingly, my aunt Diane initially provided both foods, which, after that initial consumption, was immediately followed by the onset of morning sickness.) The mere sight of either peas or smoked salmon elicited an uncomfortable queasiness that often culminated with a sprint to the porcelain throne. Apparently, this type of experience is pretty normal.
Developing an aversion to a specific tastes and smells during pregnancy is an extremely common phenomenon. In fact, between 50–90% of pregnant women worldwide experience some level of food aversion, with the most common aversions being meat, fish, poultry, and eggs. Furthermore, research suggests that food aversions developed during pregnancy are actually novel as opposed to an exaggeration of a pre-existing dislike for a certain food.
Complementing the development of food aversions is the report that dietary changes in pregnant woman are often related to changes in olfaction, or sense of smell. More specifically, some pregnant women experience increased sensitivity to certain odors, and usually in an unpleasant way. This heightened sensitivity is thought to be protective against foods that could pose a problem for mother and baby, such as those that have become rancid.
When I was pregnant, the self-perceived powerfully pungent scent of peas could have probably knocked me over if it was translated into some other physical force. I wish I had a gas mask.
Is there some benefit to morning sickness?
In general, nausea and vomiting are a defense mechanism, acting to protect us from the accidental ingestion of toxins. While morning sickness is likely a very complicated condition that needs further study, a popular explanation suggests that morning sickness is beneficial to both mother and fetus.
Several lines of observations support this idea, formally called the “maternal and embryo protection hypothesis”: (a) peak sensitivity to morning sickness occurs at approximately the same time that embryo development is most susceptible to toxins and chemical agents; and (b) women who experience morning sickness during their pregnancy are less likely to miscarry compared to women who do not experience morning sickness.
In essence, the maternal and embryo protection hypothesis suggests that morning sickness is an adaptive process, contributing to evolutionary success (measured in terms of how many of your genes are present in later generations). However, morning sickness is not found in all societies. One possible explanation for this is that those societies that do not widely experience morning sickness are significantly more likely to have plant-based diets (meats spoil much faster than plants). Another argument against evolutionary adaptation is that morning sickness has been documented only in three other species: domestic dogs, captive rhesus macaques, and captive chimpanzees.
It makes sense that the pregnancy-related nausea and vomiting widely known as morning sickness is a means to help protect mom and baby. It makes sense that women have a mechanism to detect and/or expel toxins and potentially harmful microorganisms if ingested. But the idea that morning sickness is actually a product of evolution is still under debate.
And even as a biologist, if I ever have to go through morning sickness again, the idea that it could be protective won’t really bring me comfort as I am puking up my guts. But, biology is biology and sometimes we just have to deal with it.
Andrews, P. and Whitehead, S. Pregnancy Sickness. American Physiological Society. 1990 February;5: 5-10.
Flaxman, S.M. and Sherman, P.W. Morning Sickness: A mechanism for protecting mother and baby. The Quarterly Review of Biology. 2000 June; 75(2):
Goodwin, TM. Nausea and vomiting of pregnancy: an obstetric syndrome. American Journal Obstetrics and Gynecology. 2002; 185(5): 184-189.
Kich, K.L. Gastrointestinal factors in nausea and vomiting of pregnancy. American Journal Obstetrics and Gynecology. 2002; 185(5): 198-203.
Nordin, S., Broman, D.A., Olofsson, J.K., Wulff, M. A Longitudinal Descriptive Study of Self-reported Abnormal Smell and Taste Perception in Pregnant Women. Chemical Senses. 2004; 29 (5): 391-402
[Editor's note: We are pleased to be able to run this post by Dr. Kate Clancy that first appeared at Clancy's Scientific American blog, the wonderful Context and Variation. Clancy is an Assistant Professor of Anthropology at the University of Illinois. She studies the evolutionary medicine of women’s reproductive physiology, and blogs about her field, the evolution of human behavior and issues for women in science. You can follow her on Twitter--which we strongly recommend, particularly if you're interested in human behavior, evolutionary medicine, and ladybusiness--@KateClancy.]
Over the course of my training to become a biological anthropologist with a specialty in women’s reproductive ecology and life history theory, or ladybusiness expert, I have learned a lot about miscarriage. Only it wasn’t miscarriage, it was spontaneous abortion. Except that some didn’t like the term spontaneous abortion and used intrauterine mortality (Wood, 1994). Or fetal loss. Fetal loss is probably the most common.
There is also pregnancy loss (Holman and Wood, 2001). You can use that term, too. Oh, or aContinue reading →
In the first case-based class of medical school, students are asked to answer a virtual patient’s question about the development of the fetus. These students are smart and they know all about betaHcG and are anxious to showcase their knowledge of the menstrual cycle with fluctuating levels of various hormones (FSH, progesterone, etc.). Yet one question brings confusion, “How pregnant is this woman?” The related question, “When does pregnancy start?” leaves the students flummoxed. Is it at conception? But how do you know when that happens? Or does implantation make more sense? It’s a great example of how detailed facts need the larger context.
The usual dating is gestational age, based on the first day of your last menstrual period. However, you can also date a pregnancy with embryological age, starting at conception.
How you date a pregnancy can depend on your perspective. My very general guideline:
Pregnant woman is the focus = gestational age (e.g., obstetricians) 1
Focus on embryological/fetal development = embryological age (e.g., developmental biologist) 2
But why are there two types of dates? We might need a bit of a primer on the menstrual cycle and how it relates to pregnancy.
Implantation happens between days 20 and 22. Pregnancy is often detected after the first missed period.
This graphic is intentionally simple, removing all the hormones and other fun stuff (Ed: which you can find here). You’ll note that it says approximately day 14 and day 28. In textbooks, we often see that women have 28-day cycles and everything has a nice schedule. However, women are not textbooks and sometimes have shorter or longer cycles and/or have ovulation at slightly different times. Therefore, knowing when fertilization and conception happen can be a bit tricky. An obvious marker is the first day of the last menstrual period (LMP). Why the last day? Well, another variable is the length of menses but everyone has a first day so to be consistent, that is the marker used.
We generally use gestational age when discussing pregnancy. So when someone says that they are 8 weeks pregnant, they mean it has been 8 weeks since the first day of the LMP (last menstrual period).
But that means that the first two weeks of pregnancy has nothing happening. If you are concerned about development, you don’t start counting at week 3 but start at the time of fertilization, two weeks later. Therefore, the embryological age is generally two weeks later.
But remember, we have essentially picked gestational age as the convention for discussing pregnancy dates. If there are markers in development to suggest that the embryological age is different (for example, the fetus is 12 weeks, not 13 weeks), the gestational age is often reported to the mother. In our example, the dating would be changed to 14 weeks.
Due to the difference in these dates, we see confusion beyond medical students thinking about this for the first time. It was recently reported that Arizona had changed its abortion law to be the most restrictive – but it hadn’t. It had just joined other states in making the limit 20 weeks gestational age. Remember, this is the accepted convention for pregnancy dating – but many articles picked up on that initial two weeks of nothingness in gestational age and confused it with embryological age. Was this an example of details without understanding of the greater context?
Synonyms include developmental, conception, and fetal age. ↩
Opinions expressed in this piece are those of the author and do not necessarily reflect or conflict with the opinions of DXS editors or contributors.
Dr. Catherine Anderson is a Clinical Instructor for the Faculties of Medicine and Dentistry for UBC in Vancouver, Canada. She also leads the Future Science Leaders program, helping teens excel in science and technology. She received her PhD in Medical Genetics and has spent the last 10 years helping people understand the biological sciences: the information and the impact on our lives. You can follow her on Twitter @genegeek.
There’s an old saying: You can’t be a little bit pregnant. Pregnancy is what you might call a binary condition – you either are with child, or you’re not. Home pregnancy tests embody this thinking. You pee on the end of a stick, and three minutes later you either do or do not see a line in the results window. Congratulations, you’re expecting!
Biologically, of course, things are a bit more complicated. Pregnancy tests check for the presence of a particular protein, human chorionicgonadotropin (hCG), that is also elevated in women with breast and ovarian cancers. As a result, it’s sometimes useful to be able to quantify the levels of hCG – or any other so-called “biomarker” – with a bit more precision. A new diagnostic device, developed by a team of Texas researchers and described in the journal Nature Communications, enables precisely that.
The team developed what’s called a microfluidic device, a circuit of tiny channels etched into glass (or sometimes plastic or a rubber polymer) that enable researchers to run chemical assays on tiny volumes of sample. That’s helpful when the sample is particularly precious or hard to come by – a drop of blood from a newborn baby, say.
Microfluidic devices, sometimes called “lab-on-a-chip” devices (because they resemble computer chips in both design and size), are popular in both drug development companies and research laboratories, as well as in the clinic. Their reduced volumes and size mean they use less reagent volumes (making them relatively inexpensive) and produce less waste. They are also faster and higher throughput than many traditional experiments, and are easily automated.
The downside is in the data output. To read the results of a microfluidic assay, researchers generally need some large and expensive piece of hardware that can, for instance, interrogate the chip with a laser to measure fluorescence intensity. That requirement isn’t a problem for most research labs, but it does reduce the likelihood that the technology can be adopted by your general practitioner. And it makes the development of microfluidics-based home tests, analogous to a home pregnancy kit, all but impossible.(*)
To circumvent these problems, the Texas team used a clever “SlipChip” design. A SlipChip is a microfluidic device formed by overlaying two glass plates, whose channels can form either of two flow paths depending on the position of the top plate relative to the bottom. In one configuration, the channels flow left-to-right; in the other (that is, after sliding or “slipping” the top plate), they flow bottom-to-top. Samples and reagents are loaded in one configuration, and the chip is “slipped” to start the readout process.
The SlipChip design
Source: Nat. Commun. 3:1283 doi: 10.1038/ncomms2292 (2012).
Here’s how the authors describe it:
In the SlipChip, two pieces of glass etched with microfluidic wells and channels are assembled together in the presence of mineral oil. A fluidic path is formed when the two plates aligned in a specific configuration. Samples or reagents are preloaded through drilled holes using a pipette, and the top plate is then moved relative to the bottom plate to enable the diffusion and reaction of samples or reagents.
The team calls its device a “volumetric bar-chart chip,” or V-Chip. The V-Chip runs what’s called an ELISA (enzyme linked immunosorbent assay), which is the gold standard in biomarker quantitation tests. Normally ELISAs are read with some sort of instrument that can measure either color, fluorescence, or chemiluminescence. The V-Chip is far simpler (albeit, less quantitative).
It uses an enzyme called catalase to degrade hydrogen peroxide into oxygen gas in volumes proportional to the molecule of interest – in this case, hCG. That gas, in turn, forces a column of red dye upwards to a height determined by the hCG concentration. (See the V-Chip in action here.) The result is a easy to read, microfluidic bar graph, with the height of each bar indicating not only if a woman is pregnant, but just how much hCG is in her urine. In a comparison against a commercial home pregnancy test, the V-Chip was more sensitive at low hCG concentrations, and more accurate at very high concentrations.
The V-Chip’s design is flexible, the authors note, and can be used to test either a large number of samples for a single molecule (as might be done in a clinical trial) or a single sample for multiple molecules, as in cancer screening. The current design allows as many as 50 parallel fluidic channels, meaning up to 50 molecules could be tested in parallel. In one experiment, the team used a six-channel design to test a panel of breast cancer cell lines for the abundance of three proteins (estrogen receptor, progesterone receptor, and human epidermal growth factor receptor) commonly found on breast cancer cells.
The simplicity of the test means it should be possible to design a device that can be used at home or in a doctor’s office. It is cheap, fast, and requires no special hardware. That means it could be used in areas lacking access to top-shelf medical care. It could even be used in the absence of a physician altogether. “The bar chart could be captured as an image using a smart phone, similar to a barcode reader and transmitted to a cloud computer for instant medical suggestions in the future,” the authors write. Now, how cool would that be?(*) That’s not entirely true. Harvard researcher George Whitesides has figured out a way to print microfluidic circuits onto paper, resulting in very simple and inexpensive designs. Boston-based Diagnostics For All is developing such tests for use in third world countries.
Politics often interferes where it has no natural business, and one of those places is the discussion among a teenager, her parents, and her doctor or between a woman and her doctor about the best choices for health. The hottest button politics is pushing right now takes the form of a tiny hormone-containing pill known popularly as the birth control pill or, simply, The Pill. This hormonal medication, when taken correctly (same time every day, every day), does indeed prevent pregnancy. But like just about any other medication, this one has multiple uses, the majority of them unrelated to pregnancy prevention.
But let’s start with pregnancy prevention first and get it out of the way. When I used to ask my students how these hormone pills work, they almost invariably answered, “By making your body think it is pregnant.” That’s not correct. We take advantage of our understanding of how our bodies regulate hormones not to mimic pregnancy, exactly, but instead to flatten out what we usually talk about as a hormone cycle.
The Menstrual Cycle
In a hormonally cycling girl or woman, the brain talks to the ovaries and the ovaries send messages to the uterus and back to the brain. All this chat takes place via chemicals called hormones. In human females, the ovarian hormones are progesterone and estradiol, a type of estrogen, and the brain hormones are luteinizing hormoneand follicle-stimulating hormone. The levels of these four hormones drive what we think of as the menstrual cycle, which exists to prepare an egg for fertilization and to make the uterine lining ready to receive a fertilized egg, should it arrive.
In the theoretical 28-day cycle, fertilization (fusion of sperm and egg), if it occurs, will happen about 14 days in, timed with ovulation, or release of the egg from the ovary into the Fallopian tube or oviduct (see video–watch for the tiny egg–and Figure 1). The fertilized egg will immediately start dividing, and a ball of cells (called a blastocyst) that ultimately develops is expected to arrive at the uterus a few days later.
If the ball of cells shows up and implants in the uterine wall, the ovary continues producing progesterone to keep that fluffy, welcoming uterine lining in place. If nothing shows up, the ovaries drop output of estradiol and progesterone so that the uterus releases its lining of cells (which girls and women recognize as their “period”), and the cycle starts all over again.
A typical cycle
The typical cycle (which almost no girl or woman seems to have) begins on day 1 when a girl or woman starts her “period.” This bleeding is the shedding of the uterine lining, a letting go of tissue because the ovaries have bottomed out production of the hormones that keep the tissue intact. During this time, the brain and ovaries are in communication. In the first two weeks of the cycle, called the “follicular phase” (see Figure 2), an ovary has the job of promoting an egg to mature. The egg is protected inside a follicle that spends about 14 days reaching maturity. During this time, the ovary produces estrogen at increasing levels, which causes thickening of the uterine lining, until the estradiol hits a peak about midway through the cycle. This spike sends a hormone signal to the brain, which responds with a hormone spike of its own.
Fig. 2. Top: Day of cycle and phases. Second row: Body temperature (at waking) through cycle. Third row: Hormones and their levels. Fourth row: What the ovaries are doing. Fifth row: What the uterus is doing. Via Wikimedia Commons.
In the figure, you can see this spike as the red line indicating luteinizing hormone. A smaller spike of follicle-stimulating hormone (blue line), also from the brain, occurs simultaneously. These two hormones along with the estradiol peak result in the follicle expelling the egg from the ovary into the Fallopian tube, or oviduct (Figure 3, step 4). That’s ovulation.
Fun fact: Right when the estrogen spikes, a woman’s body temperature will typically drop a bit (see “Basal body temperature” in the figure), so many women have used temperature monitoring to know that ovulation is happening. Some women also may experience a phenomenon called mittelschmerz, a pain sensation on the side where ovulation is occurring; ovaries trade off follicle duties with each cycle.
The window of time for a sperm to meet the egg is usually very short, about a day. Meanwhile, as the purple line in the “hormone level” section of Figure 2 shows, the ovary in question immediately begins pumping out progesterone, which maintains that proliferated uterine lining should a ball of dividing cells show up.
Fig. 3. Follicle cycle in the ovary. Steps 1-3, follicular phase, during which the follicle matures with the egg inside. Step 4: Ovulation, followed by the luteal phase. Step 5: Corpus luteum (yellow body) releases progesterone. Step 6: corpus luteum degrades if no implantation in uterus occurs. Via Wikimedia Commons.
The structure in the ovary responsible for this phase, the luteal phase, is the corpus luteum (“yellow body”; see Figure 3, step 5), which puts out progesterone for a couple of weeks after ovulation to keep the uterine lining in place. If nothing implants, the corpus luteum degenerates (Figure 3, step 6). If implantation takes place, this structure will (should) instead continue producing progesterone through the early weeks of pregnancy to ensure that the lining doesn’t shed.
How do hormones in a pill stop all of this?
The hormones from the brain–luteinizing hormone and follicle-stimulating hormone– spike because the brain gets signals from the ovarian hormones. When a girl or woman takes the pills, which contain synthetics of ovarian hormones, the hormone dose doesn’t peak that way. Instead, the pills expose the girl or woman to a flat daily dose of hormones (synthetic estradiol and synthetic progesterone) or hormone (synthetic progesterone only). Without these peaks (and valleys), the brain doesn’t release the hormones that trigger follicle maturation or ovulation. Without follicle maturation and ovulation, no egg will be present for fertilization.
Most prescriptions of hormone pills are for packets of 28 pills. Typically, seven of these pills–sometimes fewer–are “dummy pills.” During the time a woman takes these dummy pills, her body shows the signs of withdrawal from the hormones, usually as a fairly light bleeding for those days, known as “withdrawal bleeding.” With the lowest-dose pills, the uterine lining may proliferate very little, so that this bleeding can be quite light compared to what a woman might experience under natural hormone influences.
How important are hormonal interventions for birth control?
Every woman has a story to tell, and the stories about the importance of hormonal birth control are legion. My personal story is this: I have three children. With our last son, I had two transient ischemic attacks at the end of the pregnancy, tiny strokes resulting from high blood pressure in the pregnancy. I had to undergo an immediate induction. This was the second time I’d had this condition, called pre-eclampsia, having also had this with our first son. My OB-GYN told me under no uncertain terms that I could not–should not–get pregnant again, as a pregnancy could be life threatening.
But I’m married, happily. As my sister puts it, my husband and I “like each other.” We had to have a failsafe method of ensuring that I wouldn’t become pregnant and endanger my life. For several years, hormonal medication made that possible. After I began having cluster headaches and high blood pressure on this medication in my forties, my OB-GYN and I talked about options, and we ultimately turned to surgery to prevent pregnancy.
But surgery is almost always not reversible. For a younger woman, it’s not the temporary option that hormonal pills provide. Hormonal interventions also are available in other forms, including as a vaginal ring, intrauterine device (some are hormonal), and implants, all reversible.
One of the most important things a society can do for its own health is to ensure that women in that society have as much control as possible over their reproduction. Thanks to hormonal interventions, although I’ve been capable of childbearing for 30 years, I’ve had only three children in that time. The ability to control my childbearing has meant I’ve been able to focus on being the best woman, mother, friend, and partner I can be, not only for myself and my family, but as a contributor to society, as well.
What are other uses of hormonal interventions?
Heavy, painful, or irregular periods. Did you read that part about how flat hormone inputs can mean less build up of the uterine lining and thus less bleeding and a shorter period? Many girls and women who lack hormonal interventions experience bleeding so heavy that they become anemic. This kind of bleeding can take a girl or woman out of commission for days at a time, in addition to threatening her health. Pain and irregular bleeding also are disabling and negatively affect quality of life on a frequent basis. Taking a single pill each day can make it all better.
Unfortunately, the current political climate can take this situation–especially for teenage girls–and cast it as a personal moral failing with implications that a girl who takes hormonal medications is a “slut,” rather than the real fact that this hormonal intervention is literally maintaining the regularity of her health.
For some context, imagine that a whenever a boy or man produced sperm, it was painful or caused extensive blood loss that resulted in anemia. Would there be any issues raised with providing a medication that successfully addressed this problem?
Polycystic ovarian syndrome. This syndrome is, at its core, an imbalance of the ovarian hormones that is associated with all kinds of problems, from acne to infertility to overweight touterine cancer. Guess what balances those hormones back out? Yes. Hormonal medication, otherwise known as The Pill.
Again, for some context, imagine that this syndrome affected testes instead of ovaries, and caused boys and men to become infertile, experience extreme pain in the testes, gain weight, be at risk for diabetes, and lose their hair. Would there be an issue with providing appropriate hormonal medication to address this problem?
Acne. I had a friend in high school who was on hormonal medication, not because she was sexually active (she was not) but because she struggled for years with acne. This is an FDA-approved use of this medication.
Are there health benefits of hormonal interventions?
In a word, yes. They can protect against certain cancers, including ovarian and endometrial, or uterine, cancer. Women die from these cancers, and this protection is not negligible. They may also help protect against osteoporosis, or bone loss. In cases like mine, they protect against a potentially life-threatening pregnancy.
Are there health risks with hormonal interventions?
Yes. No medical intervention is without risk. In the case of hormonal interventions, lifestyle habits such as smoking can enhance risk for high blood pressure and blood clots. Age can be a factor, although–as I can attest–women no longer have to stop taking hormonal interventions after age 35 as long as they are nonsmokers and blood pressure is normal. These interventions have been associated with a decrease in some cancers, as I’ve noted, but also with an increase in others, such as liver cancer, over the long term. The effect on breast cancer risk is mixed and may have to do with how long taking the medication delays childbearing. ETA: PLoS Medicine just published a paper (open access) addressing the effects of hormonal interventions on cancer risk.