Part 2: From Ovulation to Conception and Fertilization of the Ovum

Pregnancy Guide and Week-by-Week Calendar
The Ovulatory Phase and Conception

> TTC Weeks 1 and 2: From Menstruation to Ovulation
> TTC Week 3: From Ovulation to Conception
> TTC Week 4: Implantation and the Luteal Phase
> Pregnancy Week 1: Early Pregnancy Symptoms & Fetal Development
> Pregnancy Week 2: What to Expect During Your First Trimester
> Pregnancy Calendar Home

In the first article in our five-part series, we discussed the early stages of your menstrual cycle – the follicular and the ovulatory phases. During these stages, which constitute the first two weeks of your cycle, your body prepares itself for ovulation. Estrogen, FSH, and LH play key roles in reproductive processes like follicular development, the building-up of the endometrium, and the maturation of the egg. Now, let’s take a look at what happens at ovulation and during the second half of your menstrual cycle, the luteal phase….

Ovulation is defined as the release of the egg from the mature ovarian follicle – the time of the month when you are most fertile. If you are trying to conceive a baby, then knowing when you ovulate is very important as you can time lovemaking during this short, “fertile window” of opportunity. Fortunately, as we explore the facts behind fertility, we’ll also look at basic physiological signs to help you predict when ovulation will take place, as well as ways to confirm the event after the fact.

During the follicular and ovulatory phases, estrogen levels are high in order to help build the endometrial lining, stimulate luteinizing hormone secretion, and facilitate the production of cervical mucus. Cervical mucus is produced inside the cervix, and as you approach your ovulation date, the amount of cervical fluids will markedly increase. Moreover, you will see changes in the look and feel of these cervical fluids. Why do these changes take place? Because cervical mucus plays an important role in human reproduction, allowing sperm to more efficiently “swim” from your vagina, through the cervical canal, and into the womb. Cervical mucus also offers protection for the sperm and will help the sperm stay alive longer (up to five days inside a woman’s body!). Therefore, the presence of fertile cervical mucus prior to and during ovulation will increase your chances of getting pregnant.

Mucus Chart

As a fertility sign, observing changes in the amount and quality of cervical mucus is a great ovulation prediction method. As you near ovulation, the amount of cervical fluids will increase and the texture will change from sticky to slippery, from dry and firm to stretchy and thin. It will also change in appearance from white or yellow to a more clear, translucent, or “egg-white” look and feel. Fertile-quality “egg-white cervical mucus” is the perfect medium in which sperm can “swimmingly” navigate their way to the egg. And when you see it, you know that ovulation is about to take place. In part one, we suggested maintaining a fertility chart or ovulation calendar. Observing changes in cervical fluids, and then writing down your daily observations on your calendar, is a central aspect of fertility charting. A product like FertileCM is effective in promoting the production of cervical mucus.

Another important estrogen-related fertility sign is “ferning”, or the crystallization of dry saliva samples that can be viewed with a special microscope. As estrogen increases, so does the quantity of electrolytes in your saliva. By viewing dry saliva samples with an ovulation microscope, you can anticipate when ovulation will take place. See the blue line in the figure above? That’s estrogen (estradiol). A “ferning” scope can tell you when you will be fertile – as much as seven days before hand!

So here we are around cycle day 14. Estrogen, dominant during the first weeks of your cycle, begins to drop and LH suddenly rises – and how! Right in the middle of your cycle, you will experience what is called the LH surge. As noted above, LH functions to wear a hole in the surface of the ovarian follicle. This breakdown in the surface of the follicle allows the egg to extricate itself and burst into the fallopian tube, the passageway leading to the uterus. Cilia, or hairlike formations, brush the egg down the fallopian tube. As noted in other articles, ovulation tests function by detecting the LH surge and are very effective in predicting fertility. A positive test result suggests that you will ovulate in the next twelve to thirty-six hours and indicates that you should make love over the following three days or so.

Ovulation directly follows the LH surge, typically around midcycle. The egg is released and can live for 24 hours, so timing lovemaking is crucial. Ovulation can be delayed or disrupted by illness, insomnia, travel, stress, or hormonal imbalances. Typically, most women will ovulate around the same time each month (depending on cycle length), though in cases of cycle irregularity, you may ovulate on different cycle days. As for physical symptoms of ovulation, there are only a few. Midcycle pains, or mittelschmerz, are experienced by some, but by no means all women, and are characterized by cramp-like pains on one side of the abdomen. An increase in libido is also a possible fertility indicator and would be a logical evolutionary-reproductive development considering that enhanced libido should lead to increased sexual activity.

Theoretically, “ovulation spotting” is also possible. Not frequently discussed, ovulation spotting is defined as a very light bleeding caused by the rupture of the ovarian follicle. As with mittelschmerz, not all women will experience this symptom, and based on the rather scant literature on this subject, ovulation spotting should be considered a peripheral ovulation symptom.

Some women may, following ovulation, experience breast tenderness. This can be confusing, as breast tenderness and nipple sensitivity is also one of the first pregnancy symptoms. If you are maintaining an ovulation calendar, any breast or nipple sensitivity right after you ovulate should not be considered a pregnancy sign, but rather a confirmation of ovulation. The most reliable indicator of ovulation (after it takes place) is measuring your basal temperature and bbt charting.

Following ovulation, estrogen slowly declines and LH drops off the map. Now, progesterone becomes the dominant hormone during the second half of your menstrual cycle, the luteal phase. See the figure above: The black line signifies progesterone, and as you can see it rises with ovulation and peaks during the middle of the luteal phase. In an interesting turn of events, what was formerly known as the ovarian follicle (which housed the maturing ovum and is now ruptured) becomes the corpus luteum. In this secondary role, the corpus luteum is the “luteal body” that secretes progesterone. Progesterone warms the body for pregnancy. This is why keeping daily records of you bbt temperatures can tell you when you ovulate each month.

Week 3: Conception and Implantation
After ovulation, the egg is swept into the fallopian tube and drifts along, brushed by waves of hairlike cilia toward the womb. If you have effectively predicted this monthly event – and timed intercourse accordingly – then between 100 and 300 million sperm may be awaiting the appearance of the solitary ovum. Some sperm are probably lost, heading in the wrong direction or up the wrong the fallopian tube, and other sperm may be neutralized by the immunity-function of white blood cells. Sounds kind of scary. In fact, of the millions of sperm that navigate their way from the vagina to the fallopian tube, only several hundred of the healthiest will meet the egg.

Fertilization: At this key junction, the question remains: Will the ovum get fertilized? Let’s see what can happen…. The sperm will typically meet the egg in the lower quadrant of a fallopian tube and start to swarm around the egg. The ovum is covered by a protective field known as the zona pellucida, and in order for fertilization to take place, sperm cells must find a keyhole (or receptor) to unlock the zona pellucida, gain entrance, and burrow their way to the oocyte, the genetic core of the ovum. Only one sperm will connect with the oocyte, precipitating genetic combination – signaling that fertilization has just taken place. With fertilization, the ovum becomes the zygote or embryo and now passes through complex phases of cell division and differentiation. You have just conceived!

Implantation: It’s often thought that fertilization and conception are synonymous with pregnancy. However, at this stage, the zygote is free-floating in the womb. In the “free floating” phase prior to implantation, cell differentiation takes place. Here, some cells will become the fetus and other cells, in a surrounding halo or constellation, will become the trophoblast, comprising the placenta, umbilical cord, and amniotic sac. For pregnancy to be successfully achieved, however, the embryo must implant in the endometrium (hence the importance of a thick, vascular-rich uterine lining). Implantation typically takes place several days and up to a week following ovulation and signals the connecting link between the mother and the fetus.

Once implantation takes place, it is the nascent duty of a protean placenta to initiate the next hormonal relay, which we will read about during week 4, from implantation through the luteal phase.

> Next… TTC Week 4: Implantation and the Luteal Phase

See Also:
> Pregnancy Week 1: Early Pregnancy Symptoms & Fetal Development
> Pregnancy Week 2: What to Expect During Your First Trimester
> Pregnancy Calendar Home