Many of you probably already know this information from sex-ed, but we thought it would be useful to compile some basic information about how our bodies work and how conception happens. Sources are cited at the end of this information, but one particularly notable source of great conception and pregnancy information is a book called Taking Charge of Your Fertility (abbreviated often to TCOYF) by Toni Weschler.
Essential ingredients: egg, sperm and mucous ... mucous?
At the most basic level, the three things that need to come together to allow conception are an egg (or ovum), some sperm, and cervical fluid or mucous. You'll see all kinds of posts and questions about what TTC-ers call EWCM -- egg-white cervical mucous. What is this fluid, and why is it so important? All month long we can observe different kinds of cervical fluids as they make their way down the vagina and onto our underwear or toilet paper. Sometimes it is sticky, sometimes is dry and barely noticeable, and sometimes it is slippery and stretchy and clear and ... looks like egg whites. It is essential for allowing healthy sperm to make their way from the cervix, through the uterus and up into the fallopian tubes. In fact, it even screens out unhealthy sperm, improving our odds of having healthy babies!
But how does this all happen, and when?
It all starts in our heads ... our pituitary glands actually. The pituitary gland releases the appropriately named Follicle Stimulating Hormone (FSH). FSH signals to the ovaries to start preparing eggs, and usually 15 to 20 eggs start maturing. Each of the eggs is housed in a follicle, which produce the estrogen that will eventually trigger ovulation (by triggering a surge in another hormone, the Luteinizing Hormone). The follicles put on a bit of a race, in that it is the most dominant follicle on one ovary that releases the egg, and the other eggs dissolve back into the ovaries.
After ovulation the egg lives for approximately 6 to 24 hours, during which time it starts its journey down the fallopian tubes. The tubes are where the action happens -- if an egg is going to be fertilized, it happens there.
This, of course, points to a fairly important piece of information about timing sex in order to achieve conception. Sperm live for up to 5 days in fertile cervical fluids, and they take a few hours to travel up to the tubes. This means it is best to have sex before or at least close to ovulation, so that the sperm can be waiting in the tubes for the egg.
In the meantime, the follicle that produced the egg is turning into what is called the corpus luteum. The corpus luteum plays a huge role in what happens after ovulation. It lasts for approximately 12 to 16 days and releases progesterone, which in turn signals to the uterus to thicken its lining in preparation for a possible pregnancy and also prevents all the other follicles from releasing an egg. In some cycles, one other egg can squeak out before the progesterone suppresses it; if both eggs were to be fertilized it would result in fraternal twins.
But what about our star eggie? As it moves through the tubes, it is either fertilized or dissolves within 24 hours of ovulation. It can take the fertilized egg approximately a week to reach the uterus. As soon as the egg begins to implant it starts releasing a hormone (Human Chorionic Gonadotropin or HCG) that tells the uterus that it needs the lining this month. The implanted egg also tells the corpus luteum to hang around longer than its usual 12 to 16 days, so that the progesterone levels needed to sustain the uterine lining are in place.
TCOYF uses the handy acronym "FELOP" to help us remember the order of hormones and events in our cycles.
F = Follicle Stimulating Hormone (FSH)
E = Estrogen
L = Luteinizing Hormone
O = Ovulation
P = Progesterone
Many of the questions on the TTC 0-12 months board focus on implantation.
"Does this look like an implantation dip on my chart?"
"Is this implantation bleeding?"
"Is this too early for symptoms?"
The truth is, it is hard to answer questions about implantation because it is hard to predict the timelines of what happens between ovulation and our periods. It takes 5 to 8 days for the egg to travel the tubes and bury itself in the uterine wall after ovulation. If you have questions about whether implantation has happened, and everyones' answers are vaguely supportive but not certain, it's because we all hope that your embryo is implanting, but no one knows for sure.
We love talking about early symptoms on this board, but we also know it can be a heartbreaking road. For some cycles we're convinced that this it it, our chart looks great, our breasts hurt, we're tired, we're hungry, we're ... not pregnant. On the other hand, some women experience no symptoms, and only figure out that they might be pregnant when they realize their period is late.
What are some typical early symptoms?
- implantation spotting between x+r and y+s days past ovulation
- some women find themselves more irritable than usual
- some women are hungrier than usual, or feel nausea
- aching breasts, larger breasts than normal, more pronounced veins (blue lines) on breasts, changes in nipple size or colour
- odd aches and twinges in or around the uterus
- heightened sense of smell
The big cautionary note about symptoms is that most early pregnancy symptoms are a lot like pms symptoms. This is because after ovulation and up to our period, the hormone progesterone remains high whether we are pregnant or not until a few days before our period when progesterone drops off. Progesterone can make our breasts hurt, make us feel queasy, reduce energy levels ... all those symptoms can be either pregnancy or a sign that our periods are coming.
What are my odds?
The average couple has 25% chance of conceiving in a cycle, a percentage that does drop as we age.
So how do I know if I'm pregnant?
If you are charting, TCOYF tells us that 18 days of temperatures above your cover line mean you are pregnant.
But what if you don't want to wait that long to find out? Pee on a stick (POAS)! Home pregnancy tests vary in sensitivity, but all detect the pregnancy hormone HCG and report either positive (pregnant) or negative (not pregnant) if enough HCG is present in the urine. First morning urine is best for home pregnancy tests. Sometimes doctor confirm pregnancies with a blood pregnancy test, which is far more sensitive, sometimes able to detect as little as HCG levels of 5.
The test was negative, but I feel pregnant -- are you sure I'm not pregnant?
Women who are trying to conceive can experience a great deal of anxiety between ovulation and when they find out if they are pregnant or not. The two-week-wait can be excruciating! Sometimes in our excitement we test too early, before hcg levels are detectable. On the other hand, it is possible that you are not pregnant -- don't forget that pre-menstrual symptoms can mimic pregnancy symptoms. If your period is late and home pregnancy tests are still saying that you're not pregnant, it might be wise to call your doctor to see if he or she can schedule a bloodtest for you.
Unfortunately, at least 25% of pregnancies can end in miscarriage, and that number may be higher given that many miscarriages occur before a woman knows that she is pregnant. It can be heartbreaking, and if it happens to you it doesn't always help to know that there are many women on this site who have experienced a similar heartbreak. Everyone processes grief differently, but if you think it might be helpful to you, we have boards devoted to supporting women who have experienced a miscarriage and also for those who want to try to conceive after a loss.
Sources used in compiling this information:
Taking Charge of Your Fertility, Toni Weschler, particularly chapter 4 and Appendix E
Wikipedia entries on: Follicle Stimulating Hormone, the menstrual cycle, and miscarriage. The entry on miscarriage has a very helpful set of definitions of the various terms our doctors use when describing miscarriages.