In this session, Dr Elena Santiago, Gynaecologist & Fertility Specialist at Clinica Tambre, Madrid, Spain, discussed the fertile window and its importance when you’re trying to conceive.
Dr Santiago starts by discussing women’s physiology as it relates to age. She explains that it is very important to understand that women are born with all their eggs inside their ovaries. This means that they will not produce any new eggs throughout their lifetime. The number of eggs is typically around two million at birth, but approximately 11,000 of them will die each month before puberty. While women start with many eggs, this number begins to decline as soon as they are born and continues to decrease throughout their lifetime.
Once a woman reaches puberty, which typically occurs between the ages of 10 and 16, her menstrual cycle will begin. This process involves the production of hormones in the brain that will mature the genital tract, ultimately leading to fertility. This stage also marks a significant period of bone growth, and secondary sexual characteristics will develop during puberty. As is well known, the first menstruation, called menarche, marks the beginning of fertility, and from this point onward, a woman can conceive with each cycle. While it is true that menstrual cycles may start irregularly, this varies from woman to woman, but once a period begins, fertility is established, and pregnancy can occur.
Dr Santiago says that, as a teenager, a woman has approximately 300,000 to 400,000 eggs remaining. From this point onward, she will lose about 1,000 eggs each month. This phenomenon occurs independently of hormonal production. For example, even if a woman is taking birth control pills, she will still lose the same amount of eggs, even though ovulation is suppressed by the pill. Similarly, during pregnancy, although menstrual cycles are absent, the loss of eggs continues. Even when taking nutritional supplements to improve ovarian reserve, egg loss remains unchanged. While lifestyle factors can affect the quality of eggs, they do not impact the quantity. It is important to understand the dynamics of ovarian stimulation during assisted reproductive treatments, as some women worry that they will lose many eggs due to the stimulation. However, the truth is that they will lose the same number of eggs as in a natural cycle. Eventually, when a woman runs out of eggs, her ovaries will no longer produce estrogen, and she will enter menopause.
Thus, the presence of eggs signifies a woman’s fertility period, and once they are gone, pregnancy is no longer possible.
Dr Santiago highlights it is very important to understand the menstrual cycle to identify the fertility window. The key components that regulate the ovaries’ function are controlled by the brain. First, the hypothalamus produces GnRH, which stimulates another part of the hypothalamus to produce FSH and LH, known as gonadotropins. These hormones travel through the bloodstream to the ovaries, where they stimulate the ovarian cycle. As the ovaries begin to function, they also produce hormones such as estrogens and progesterone. These hormones, in turn, act on the uterus to prepare the endometrium, the lining of the uterus, where implantation must occur.
A menstrual cycle begins with the first day of a period, which is important to note. During this time, hormonal production from the brain causes levels of FSH and LH to rise, with FSH being higher during the first phase, known as the follicular phase, leading up to ovulation. The second phase is called the luteal phase, which begins after ovulation. In the follicular phase, several follicles are present in the ovaries. If ovarian reserve is good, there are typically 10 to 20 follicles, and FSH causes some of these follicles to grow. One follicle becomes dominant, growing larger than the others, and is selected to produce ovulation. Ovulation occurs around the middle of the cycle in response to a peak in LH levels, which triggers the release of the egg into the fallopian tube. After ovulation, the remaining follicle in the ovary becomes the corpus luteum, which is crucial as it produces the hormone progesterone. Estrogens are primarily produced in the first phase of the cycle, while progesterone is produced after ovulation by the corpus luteum. These hormones, estrogens and progesterone, act on the endometrial lining. When a period occurs, the endometrial lining is shed, and the tissue is renewed for the next cycle. Estrogens promote the growth of the endometrium, while progesterone matures it, preparing it for potential implantation if the released egg is fertilized.
Dr Santiago explains the process of fertilization and implantation. After the egg is released from the ovary, it travels to the fallopian tube, where it must meet the sperm for fertilization to occur. If fertilization happens, the egg starts dividing into an embryo, which continues travelling through the fallopian tube. It eventually reaches the uterus, where the endometrium is prepared for implantation. This process typically occurs between days five to eight after fertilization. The entire procedure takes about six to eight days after ovulation, which typically occurs around the middle of the cycle. It is important to note that the egg survives only 24 to 48 hours after being released. On the other hand, sperm, once introduced during sexual intercourse, travels upwards through the uterus and into the fallopian tubes, where it can survive for several days—around 72 hours if the sperm sample is healthy. This timing is crucial for achieving pregnancy.
Dr Santiago explains that identifying ovulation can be done not only by using a calendar but also by recognizing symptoms that many women experience. While not every woman will have these symptoms, various clues can indicate when ovulation is occurring, and learning to detect them can be quite helpful. For example, some women may experience abdominal pain, similar to menstrual cramps, although it is usually less intense. Other symptoms include an increase in vaginal discharge, which becomes more transparent than at other times in the cycle during the fertility window. Additionally, it is natural for libido to increase during ovulation, which may unconsciously make a woman more interested in sexual intercourse. Lastly, basal body temperature tends to rise during ovulation, which can also help women identify their fertile days.
Dr Santiago explains that a third way to identify the fertility window is by using ovulation tests. These tests are inexpensive, easy to use, and only require a urine sample, making them convenient to perform at home. When ovulation occurs, a red line will appear on the test, indicating that ovulation will happen within 24 to 48 hours. She advises that these tests should be done at least once a day at the same time, although testing in the morning and evening may provide better results. While ovulation tests can help detect the exact timing of ovulation, Dr Santiago notes that they do not necessarily increase the chances of pregnancy compared to women who do not use them. However, they can help pinpoint the fertility window.
Moreover, Dr Santiago emphasizes the importance of age in pregnancy chances. While identifying ovulation is crucial for conception, it is equally important to be aware that age significantly affects fertility. According to the fertility timeline, ages between 18 and 24 are the most optimal for getting pregnant, as this is when it is easiest to conceive. Ages between 25 and 30 are still favourable, but from 30 years old onwards, pregnancy becomes more challenging. This is due to both a lower ovarian reserve and a decrease in the quality of the remaining eggs, leading to a reduced chance of pregnancy as age increases.
Dr Santiago explains the impact of age on infertility and the likelihood of getting pregnant. As she mentioned before, fertility is very high in our 20s, but it significantly decreases around the age of 35 to 40. Therefore, the likelihood of infertility increases with age. However, it is important to understand that the chances of getting pregnant in any given cycle are not as high as one might expect. Humans are not highly fertile organisms, and the maximum chance of getting pregnant in one cycle is about 20%. This percentage represents the likelihood of achieving pregnancy over an entire year, not within a single cycle. Consequently, it is important to understand that achieving pregnancy is not always easy or quick, and many couples may need to try for several months before succeeding.
Dr Santiago discusses medical advice regarding the fertility window when trying to conceive. She emphasizes the importance of being aware of one’s cycle but also warns against becoming overly obsessed with it. It’s essential to let nature take its course, as even libido naturally increases during ovulation days. However, being aware of one’s body can provide valuable information and potentially increase the chances of conception.
Having sexual intercourse two to three times per week is generally sufficient to maximize the chances of pregnancy, even if it is not timed precisely with ovulation.
If there are no fertility issues, regular intercourse should be enough. Dr Santiago also notes that the maximum probability of success in any given cycle is about 20%, which decreases significantly starting at age 35. For women under 35, it is advised to try for a year to conceive, and if unsuccessful, consult a doctor for further tests. For women over 35, the recommendation is to try for six months before seeking medical advice. Additionally, Dr Santiago advises women who wish to have children later in life to consider freezing their eggs in their twenties to preserve fertility and avoid challenges when trying to conceive at an older age. This option provides the opportunity to use high-quality, frozen eggs in the future, improving the chances of successful pregnancy.
To conclude, Dr Santiago emphasizes the importance of being aware of one’s cycle when trying to conceive. She advises understanding your body without becoming obsessed, and being mindful of the impact age can have on fertility. If a woman is not in her twenties, but in her thirties or forties, she may need to try for a maximum of six months before seeking medical assistance. Identifying the fertility window through methods such as following a calendar, recognizing symptoms, and using ovulation tests can help maximize the chances of getting pregnant.
It is your period because it’s true that sometimes women experience spotting during ovulation, which is a little bleeding during those days. Maybe you are counting that as your period, but it’s actually ovulation, and your period will come two weeks later. If this is not the case and there’s no spotting, then the LH surge may not happen before your period. I’m not sure if this is working correctly for you right now. Sometimes, you can also have an LH surge if you’re getting pregnant, and afterwards, if the pregnancy doesn’t work out, we call it a biochemical miscarriage. So, if it’s not just spotting as I mentioned, my advice is to ask a doctor to help you with this LH surge.
Okay, honestly, I don’t know much about apps, sorry about that, because there are millions of them, and they vary in different countries. However, I think they are good. Normally, they are quite accurate, even if you have cycles that aren’t very punctual. They can help you detect the fertility window that we’ve spoken of. So, they are useful. They also help you remember when you had your last period, so you can calculate when your fertility window is. This way, you can check that you’re regular and that you’re having periods every month. I think they are helpful in that regard.
Perhaps some of your cycles are not always ovulatory. This doesn’t mean that at 24 I won’t have ovulation, but at 26 I will, okay? Sometimes, shorter cycles can be anovulatory. So, in your case, it would be very good to check for ovulation around the middle of the cycle, as we mentioned, with an ovulation test if you’re having these shorter cycles, just to make sure everything is alright.
Perhaps you should check with the doctor as well because sometimes if you’re having a real period, it’s important to check that you have good progesterone levels during the second luteal phase we talked about. Sometimes, you may have ovulation, but afterwards, your ovary might not produce enough progesterone. This means that a period could come because there isn’t enough hormone to sustain the endometrium in place, and then you’ll get your period. Ask a doctor about this, and maybe check your progesterone levels in the luteal phase after your LH surge.
Our inheritance is indeed important, for example, for the age at which we start our period or experience menopause, so we might have similar patterns to our mothers. However, this doesn’t mean that 10 years before menopause is the final timing for when you can get pregnant. This depends more on your ovarian reserve. As I said, even if you have a very good ovarian reserve at 45 years old—which I’ve seen in some patients, although it’s rare—it exists. But you have to take into account that, at these ages, fertility will be significantly diminished for absolutely every woman. So, while it’s not impossible to achieve a pregnancy at 43, 44, or 45 years, it’s very, very difficult for everyone. We don’t have a strict timeline in that sense, so it’s better to assess the actual situation with a fertility study that includes measuring our anti-Müllerian hormone and antral follicle count to understand more about our ovarian reserve. Unfortunately, there are no tests that can check egg quality, which is a problem. As I said, we always need to consider that from 40 years onwards, and especially after 42 years, egg quality starts to decline significantly. At 45 years, it is typically very, very difficult because of egg quality, even if your mom had a late menopause.
Let’s say that it’s not normal. As I mentioned, typically, cycles will be between 25 and 35 days. If you’re having 2 periods a month, this could sometimes indicate something, such as a low ovarian reserve right now. I’m not saying that you have this, but it might be something we need to check with our gynaecologist to see whether everything is alright hormonally and whether you have a good ovarian reserve. It’s true that even years before menopause, we can experience irregular cycles, meaning we might have periods twice a month or even go 1, 2, or 3 months without a period, then get another one. Irregular periods can sometimes suggest that hormonally something isn’t working correctly, or they could be signalling that we’re heading toward menopause in a few years. I don’t know more about you, so I’m not saying you have a low ovarian reserve. I’m just suggesting that it would be good to check with your doctor to be sure everything is okay.
As we’ve explained, this is not an exact science; biology never is. Things happen, as I mentioned, hormonally—there needs to be stimulation, followed by a peak of LH and ovulation, and this can vary. Just like any other procedure in our bodies, it can vary. This doesn’t mean that having one menstrual cycle of 28 days and the next 30 days is unusual—it’s quite normal. So, don’t worry about that, because biology works like that.
Regarding IVF, there isn’t a strict maximum age. Clinics usually set a maximum age due to the chances of success. For IVF with one’s own eggs, the typical maximum is around 45 to 46 years, assuming there is a good ovarian reserve. Honestly, I’ve never seen IVF done with women around 50; that’s typically when egg donation treatments are used. The limitations aren’t because periods stop at 50, but rather due to the increased risks associated with pregnancy at that age. We have to set a limit, usually around 50, because, after that, there are higher risks for complications during pregnancy.
Egg donation can always be done, even for women in menopause, with very good chances of success. Biologically, this is achievable because, with hormonal treatment, the uterus can be prepared for implantation, even if the ovaries are no longer functioning. For example, egg donation can work for women aged 55 or even 60. However, the main limitations are the risks during pregnancy, particularly from age 50 onwards. We have to consider the possibility of premature delivery, preeclampsia (a severe illness with hypertension, which increases with age), and gestational diabetes, all of which pose risks to both the mother and the baby. These are the reasons why there are age limitations, and it’s important to be aware of these risks.
Inheritance is important, and you may indeed have more chances to get pregnant because of these events from your grandmother and great-grandmother. However, as I always say, each person’s situation is different. For every woman, getting pregnant after 40 years old is going to be more difficult. I’m not saying it’s impossible, but age can make it more challenging. That said, your inheritance might mean that you have a good ovarian reserve, as you mentioned—14 follicles is very, very good for your age. The other issue we need to consider is egg quality.
Yes, you can achieve pregnancy, but I can’t predict the future. My advice is that you try naturally for six months, and if you don’t achieve pregnancy by then, even if you’ve had a child before, I recommend seeking help for an IVF treatment. That could potentially increase your chances of getting pregnant.
I understand you perfectly because I have patients over 40 years old every single day with the same problem. I’m not saying that we can’t achieve a pregnancy, I’m only saying that it’s going to be more difficult. It’s not that we are old—today, a 40-year-old woman is very young because we live much longer than before. However, the problem is that our own biological clock hasn’t changed with society, so when we say we’re 40 years old, we are considered a little older, and we have fewer chances of success. This is something that, for now, can’t be changed if we want to use our eggs. As I said, maybe you can still have a pregnancy, but if it’s been difficult, my advice is to consider treatment before it becomes too late.
There is no strict limitation here. As I say, the limits are typically age-related. You can try as many attempts as you want, but normally, if you’ve been through, for example, two embryo transfers that didn’t work, even with very good quality embryos from a donor, then we would need to see if there are other issues. Typically, this would mean we could ask for more tests, such as checking the uterus or assessing blood clotting if you have a problem with that, to see if any other factors could be affecting implantation.
There is no maximum number of attempts; you can try as many as you want. However, this process is also psychologically very difficult, so we always have to acknowledge that each person has their own limit. Medically, the only limitation would be age, but I would recommend that if you’re going ahead with another treatment, you might want to look into other things that were not tested before, as they could potentially explain why we haven’t had success with implantation so far.
It’s very difficult to know your exact percentage, but obviously, we are around that percentage because of the egg quality, as I mentioned. This means that most of the embryos we can achieve, either naturally or through IVF treatment, could be chromosomally abnormal. So, the chances of getting pregnant are going to be much lower than before, and even the miscarriage rates are going to be higher. I can’t give you a specific percentage, but my advice is that if you’ve already been trying for 3 years and haven’t achieved a successful pregnancy, you should probably consider treatment to increase your chances.
Insemination is normally not an option from 38 years onwards, so I think that the option, obviously, will be IVF. However, we would need to know much more about you to give you the best advice. But normally, yes, that would be the treatment for you.
The greater the number of eggs in one cycle, the better. I mean, we could always accumulate eggs to have better chances, meaning to have more embryos in an IVF treatment. But normally, it’s true that not only age but also ovarian reserve, sometimes if it’s very low earlier than expected, can mean that the quality could be worse than what age alone might suggest. I mean, the better the response to treatment, normally—though not always—the quality should be better, and at least the chances are going to be better than in a treatment where we achieve fewer eggs.
I mean, normally, egg quality is constant. It doesn’t mean that all the eggs are going to be the same, but if we can have a general idea, normally if the quality is bad, it will be that way throughout all cycles. And if the quality is good, it should stay that way. This is biology, as I say, as you say.
So, obviously, in a person with very bad-quality eggs, we could always achieve a good egg that develops into a good embryo and, obviously, into a developing pregnancy. But, I mean, if we’ve been through many treatments and the quality is always bad, then maybe the advice is to change the eggs, for example, with egg donation. I mean, there is no treatment for egg quality. That’s the difficult part, yes.
