What could be causing irregular bleeding during the second week of my Loestrin (ethinyl estradiol and norethindrone) pill regimen after 9 months of use?

From the Guidelines

Irregular bleeding during the second week of your Loestrin pill regimen after 9 months of use is likely due to an underlying health condition, such as interactions with other medications, sexually transmitted infections (STIs), pregnancy, thyroid disorders, or new pathologic uterine conditions, which should be investigated and treated if found, as recommended by the 2024 U.S. Selected Practice Recommendations for Contraceptive Use 1. To address this issue, it's essential to explore patient goals, including continued use of the Loestrin pill or consideration of alternative contraceptive methods.

• If an underlying health condition is suspected, it's crucial to investigate and treat the condition or refer for care, as suggested by the guidelines 1.
• Some treatment options may be considered to manage bleeding irregularities, such as hormonal treatment, antifibrinolytic agents, nonsteroidal anti-inflammatory drugs (NSAIDs), or selective estrogen receptor modulators (SERMs), depending on the patient's preferences, treatment goals, and medical history 1. Key considerations include:
• Checking for consistent pill intake and timing, as deviations can affect hormone levels and cause breakthrough bleeding.
• Ruling out medication interactions, such as antibiotics, antiseizure drugs, or herbal supplements like St. John's Wort, which can reduce the effectiveness of birth control pills and cause irregular bleeding.
• Investigating lifestyle factors, such as significant stress, major weight changes, or illness, which can disrupt hormonal balance. If the irregular bleeding continues or is accompanied by concerning symptoms, consulting a healthcare provider is necessary to determine the best course of action, which may include switching to a different formulation or ruling out other conditions like infections, polyps, or fibroids, as recommended by the guidelines 1.

From the FDA Drug Label

Irregular vaginal bleeding or spotting may occur while you are taking drospirenone and ethinyl estradiol tablets. Irregular bleeding may vary from slight staining between menstrual periods to breakthrough bleeding, which is a flow much like a regular period. Irregular bleeding occurs most often during the first few months of oral contraceptive use, but may also occur after you have been taking the pill for some time.

The cause of irregular bleeding during the second week of your Loestrin (ethinyl estradiol and norethindrone) pill regimen after 9 months of use could be due to hormonal changes. It is not uncommon for women to experience irregular vaginal bleeding or spotting while taking birth control pills, even after several months of use. However, if the bleeding occurs in more than one cycle, is unusually heavy, or lasts for more than a few days, you should call your healthcare provider 2.

From the Research

Causes of Irregular Bleeding

• Hormonal changes: The combined oral contraceptive pill (OCP), such as Loestrin, contains estrogen and progestin, which can affect menstrual bleeding patterns 3.
• Breakthrough bleeding: This is a common side effect of OCPs, especially during the first few months of use, but can also occur after 9 months of use 3.
• Progestin potency: The type and dose of progestin in the OCP can influence bleeding patterns, with higher progestin potency associated with fewer bleeding days 3.

Factors Influencing Menstrual Bleeding

• Estrogen and progestin ratio: The balance between estrogen and progestin in the OCP can impact menstrual bleeding, with some studies suggesting that a higher estrogen dose can reduce bleeding days 3.
• Individual variability: Women's responses to OCPs can vary, and some may experience irregular bleeding despite being on the same regimen for an extended period 3.

Potential Effects of Loestrin on Menstrual Bleeding

• Loestrin contains ethinyl estradiol and norethindrone, which can affect menstrual bleeding patterns, but the specific effects on irregular bleeding during the second week of the pill regimen are not well-studied 4, 3.
• The progestin component of Loestrin, norethindrone, has been shown to have a moderate potency, which may influence bleeding patterns 3.

Comparison with Other Contraceptives

• Other combined hormonal contraceptives, such as the contraceptive vaginal ring (CVR), have been studied for their effects on menstrual bleeding, but direct comparisons with Loestrin are limited 5.
• The levonorgestrel-releasing intrauterine system (LNG IUS) has been shown to be more effective in reducing menstrual blood loss compared to combined oral contraceptives, but its effects on irregular bleeding during the second week of the pill regimen are not well-studied 5.