Many women reach perimenopause with a very common belief: when the menstrual cycle starts to become irregular, fertility is over.
In reality, this is precisely the stage when one of the most frequent confusions in women’s health after forty begins.
Perimenopause does not coincide with the end of fertility.
It coincides with the end of its predictability.
And that is an important difference.
For this reason some women discover an unexpected pregnancy when they thought it was no longer possible, while others, in the very same years, encounter difficulties when trying to conceive. It is not a contradiction. It is the result of the way the reproductive system changes during the menopausal transition.
Understanding what is actually happening in the body allows informed decisions, whether a pregnancy is desired or whether it should be avoided.
What is perimenopause and what happens to the ovaries
Menopause is defined as the absence of menstruation for twelve consecutive months. Everything that happens before belongs to perimenopause, a phase that can begin around the age of forty and last several years.
As explained by the American College of Obstetricians and Gynecologists, the menopausal transition is characterized by progressive variations in ovarian function and not by a sudden interruption of reproductive activity.
During perimenopause the ovaries do not suddenly stop working. They continue producing hormones, but they do so irregularly. The first change concerns ovulation, which no longer occurs with the regularity typical of the fertile years.
Progesterone tends to decrease because many cycles become anovulatory. Estrogen instead fluctuates. It can be low in some months and relatively high in others. This explains why some women experience hot flashes while others, in the same period, have breast tenderness, heavy cycles, or symptoms that change rapidly.
From an endocrinological perspective, perimenopause is a phase of hormonal variability rather than a stable hormonal deficiency, as also described by the North American Menopause Society clinical recommendations on the menopausal transition.
As long as even a single ovulation can occur, pregnancy remains biologically possible.
Can you get pregnant in perimenopause?
Yes, it is possible.
Fertility decreases with age but does not disappear before established menopause. The presence even of sporadic menstruation indicates that ovarian activity has not yet ceased. Ovulation can occur even after weeks or months of apparent inactivity.
The key point is that ovulation becomes unpredictable.
A woman may have very distant cycles and ovulate in isolation without evident signals. If that moment coincides with unprotected intercourse, conception can occur.
This unpredictability explains many unexpected pregnancies after forty. Educational fertility materials also highlight that, during perimenopause, ovulation may appear sporadically and cannot be reliably predicted.
Why fertility after 40 decreases but does not disappear
Fertility is not an on-off switch. It is a progressive process.
With age ovarian reserve decreases and, above all, oocyte quality changes. Oocytes more frequently present chromosomal abnormalities, reducing the probability of conception and increasing the risk of miscarriage.
The American College of Obstetricians and Gynecologists describes fertility decline as a continuous biological phenomenon that accelerates after age 37 but does not abruptly stop.
According to the American Society for Reproductive Medicine, the monthly probability of natural pregnancy decreases to around 10% at age forty and becomes even lower after 45. It is not a high probability, but it is still real.
Less likely does not mean impossible. During perimenopause, fertility still exists, but it is inconsistent.
What happens after 45
After 45 natural fertility becomes much rarer, but not impossible. The reduction in ovarian reserve is marked and oocyte quality is more frequently compromised; however, the ovaries may still occasionally produce oocytes.
The main change concerns the probability that an embryo is genetically healthy. With increasing age, chromosomal abnormalities linked to oocyte cell division become more frequent. For this reason, even when conception occurs, the likelihood of miscarriage in the first weeks increases.
This does not represent an absolute contraindication to pregnancy but a condition requiring closer medical monitoring.
Irregular cycles and ovulation: why it is difficult to predict
For years many women use cycle regularity as a fertility indicator. During perimenopause this reference loses reliability.
Months without ovulation may be followed by a late ovulation. Some cycles are shorter, others much longer. In some situations ovulation may occur even before the first menstruation after a long interval.
For this reason natural methods based on calendars or fertile-day counting become unreliable. It is not possible to establish with certainty when ovulation will occur.
Unexpected pregnancy in this phase does not depend on high fertility but on the difficulty of anticipating the single fertile moment.
Can you get pregnant without having a period?
A frequent question concerns temporary absence of menstruation. Many women interpret several months without a period as a sign that menopause has already occurred.
In reality ovulation always precedes menstruation. This means that the first ovulation after a long interval may occur before the first subsequent cycle. In other words, ovulation can occur without having had menstruation in the preceding months.
If unprotected intercourse happens in that period, pregnancy is possible even without recent cycles.
If you do not want a pregnancy: contraception is still necessary
One of the most common misunderstandings is stopping contraception when the cycle becomes irregular.
Recommendations on contraception in women over 40 emphasize that fertility may persist throughout perimenopause and protection should be maintained until menopause is confirmed.
Menopause can only be diagnosed after twelve consecutive months without menstruation. Before that moment ovarian activity may still resume.
If you desire a pregnancy
When pregnancy is sought, the most important factor becomes biological time.
After forty it is not advisable to wait long before specialist evaluation. Understanding whether ovulation is still present and assessing ovarian reserve helps guide: it does not necessarily mean immediately resorting to assisted reproduction, but understanding real possibilities and monitoring ovulation.
Risk of miscarriage and why it increases
One of the most delicate aspects of pregnancy in perimenopause concerns early pregnancy loss. It depends mainly on the genetic quality of the oocyte.
With age the probability of chromosomal distribution errors during oocyte division increases. If the embryo has an incorrect chromosome number, pregnancy often stops naturally in early stages. It is a biological mechanism.
Metabolic impact of pregnancy after 40
As maternal age increases, not only does the probability of conception change, but also the body’s metabolic response to pregnancy. Gestation is, in itself, a physiologically demanding condition: it increases energy requirements, modifies insulin sensitivity, changes blood pressure, and requires important cardiovascular adaptations. After forty, these adaptations may become more complex.
One of the main aspects concerns glucose regulation. With age, the likelihood of reduced insulin sensitivity increases. During pregnancy, especially in the second and third trimester, the body becomes physiologically more insulin resistant in order to ensure adequate energy supply to the fetus. If this overlaps with age-related metabolic predisposition, the risk of gestational diabetes may increase. The guidelines of the American College of Obstetricians and Gynecologists and the World Health Organization identify advanced maternal age as a major risk factor for this condition.
Another element concerns blood pressure. Pregnancy requires significant cardiovascular adaptation: circulating blood volume increases and the heart works harder. After 40, particularly in the presence of risk factors such as overweight or family history of hypertension, the likelihood of developing gestational hypertension or preeclampsia increases. Again, this is not an inevitable outcome but a greater vulnerability that requires careful monitoring.
There is also the aspect of lipid metabolism. During pregnancy, triglycerides and cholesterol physiologically increase. In an organism already characterized by metabolic changes typical of perimenopause, this increase may be more pronounced. For this reason, a balanced lifestyle before conception becomes even more important than at younger ages. If you are experiencing cycle changes or doubts about the phase you are going through, it may be useful to better understand how to recognize perimenopause.
It is important to underline that “greater risk” does not mean “negative outcome.” Many pregnancies after 40 proceed without complications. However, pre-conception evaluation and personalized monitoring allow early identification of possible issues and timely intervention.
From a clinical perspective, discussing metabolic impact is not meant to discourage but to prepare. A pregnancy at this stage of life requires greater awareness, more prevention, and structured medical support. With the right information and adequate guidance, it can be experienced with serenity and safety.
Tests that help understand fertility in perimenopause
Some tests provide useful indications, although they cannot predict pregnancy with certainty.
Anti‑Müllerian hormone offers an estimate of ovarian reserve. FSH and estradiol help evaluate ovarian response. Transvaginal ultrasound with antral follicle count completes the assessment.
Do you have doubts about your fertility?
If you recognize yourself in these changes or have questions about pregnancy at this stage of life, you can speak with a gynecologist specialized in perimenopause from the Pausetiv team.
A personalized evaluation helps understand what is really happening in your body and which options are most appropriate for you.
Book an orientation call with Pausetiv.
