Perimenopause is the transitional phase preceding menopause, marking the natural slowing of reproductive function. This period begins when the ovaries gradually produce fewer hormones and typically lasts for several years. Many people mistakenly believe that once perimenopause starts, the ability to conceive ends entirely. However, fertility is diminished but not fully eliminated, meaning perimenopause does not equal infertility.
How Fertility Changes During Perimenopause
The decline in fertility is rooted in changes to the ovarian reserve, the remaining supply of viable eggs. The number and quality of eggs steadily decrease throughout reproductive life. By perimenopause, the pool of remaining follicles is smaller, and released eggs are more likely to have chromosomal abnormalities, increasing the risk of early pregnancy loss.
Fluctuating hormone levels, particularly estrogen and progesterone, directly impact the regularity of the menstrual cycle. Estrogen levels can swing widely, and while the body attempts to compensate by increasing follicle-stimulating hormone (FSH), the response from the aging ovaries is inconsistent. This hormonal variability often leads to erratic or skipped ovulations, making the timing of conception a challenge.
Menstrual cycles often become irregular, varying in length, flow, and timing. Ovulation may occur less frequently, or cycles may become anovulatory, meaning no egg is released. While the likelihood of becoming pregnant decreases significantly, it is not zero. As long as a period is still occurring, even sporadically, spontaneous ovulation remains a possibility.
Continued Need for Contraception
Since ovulation remains possible, even if erratic, birth control is still necessary for individuals who wish to prevent pregnancy. Pregnancy rates drop as the menopausal transition advances, but unintended pregnancy remains a risk until full menopause is confirmed. A notable percentage of women in their mid-to-late 40s still become pregnant without contraception.
Contraception should be continued until a healthcare provider confirms that menopause has been reached. For individuals under the age of 50, some guidelines recommend continuing contraception for two years following the last menstrual period to account for long intervals between cycles. Hormonal birth control methods, such as combined hormonal contraceptives, can also help regulate irregular bleeding and manage symptoms like hot flashes.
Discuss contraceptive options with a medical professional, as age-related health changes, such as increased risk for cardiovascular issues, may limit the suitability of certain methods, particularly those containing estrogen. Some hormonal methods, like progestin-only options, can also mask the irregular cycles that signal the progression of perimenopause. A doctor can help determine the most appropriate method that balances pregnancy prevention with symptom management.
Strategies for Conceiving
For individuals trying to conceive during perimenopause, the primary challenge is the uncertainty of ovulation. Even with irregular cycles, tracking methods like monitoring basal body temperature and cervical mucus can help identify the less frequent fertile windows. Ovulation predictor kits, which detect the surge of luteinizing hormone (LH), can also be helpful, though they may be harder to interpret with highly fluctuating hormones.
If natural conception attempts are unsuccessful, a fertility specialist can perform assessments to determine the remaining reproductive potential. Common tests include the Anti-Müllerian Hormone (AMH) blood test, which estimates the ovarian reserve. Elevated Follicle-Stimulating Hormone (FSH) levels, especially when measured early in the menstrual cycle, can also indicate declining ovarian function.
Assisted Reproductive Technologies (ART), such as in vitro fertilization (IVF), offer a medical pathway to conception, though success rates decline significantly with age due to egg quality. For women over 40, IVF success rates using their own eggs are considerably lower. Using donor eggs from a younger individual can dramatically improve the chances of a successful pregnancy, as egg health is the main limiting factor.