Irregular Periods: Causes, Pregnancy Risks, and Medication Effects - Obstetrics and Gynecology

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Irregular menstrual cycle?


Hello, I would like to ask about my girlfriend's menstrual cycle, which has been quite irregular, with cycles of 28, 33, 35, 38, and 42 days.
Her last menstrual period was from October 31 to November 7.
Since then, we have had sexual intercourse on many days, but we used protection each time.
On December 6, my girlfriend had a cold and went to see a doctor, where she took cold medication but did not recover.
She went back to the doctor on December 9 and took more cold medication.
On December 11, she took a pregnancy test, which showed one line.
It has been 45 days since her last menstrual period, and on December 13, she took another pregnancy test, which also showed one line.
She is still taking cold medication.
Will taking cold medication affect her menstrual cycle? What could be the reason for her missed period? Are the pregnancy tests on December 11 and 13 accurate? What is the likelihood of pregnancy?

Xiao Wu, 20~29 year old female. Ask Date: 2023/12/15

Dr. Chen Zhiyu reply Obstetrics and Gynecology


Hello, regarding delayed menstruation, it is recommended to visit a gynecology clinic for evaluation.
Thank you.

Reply Date: 2023/12/15

More Info


Understanding irregular periods and their implications for pregnancy can be quite complex, especially when medications and other health factors are involved. Irregular menstrual cycles can be caused by a variety of factors, including hormonal imbalances, stress, significant weight changes, and underlying health conditions. In your girlfriend's case, her cycle lengths ranging from 28 to 42 days suggest that she may have a condition known as oligomenorrhea, which is characterized by infrequent menstrual periods.

The fact that your girlfriend has had several instances of sexual intercourse with protection reduces the likelihood of pregnancy, but it does not eliminate it entirely. Condoms are generally effective, but no contraceptive method is 100% foolproof. If she has missed her period, it is important to consider other factors that could contribute to this delay.

Regarding the medications she has taken for her cold, certain over-the-counter cold medications can potentially affect menstrual cycles, although this is not common. Ingredients such as pseudoephedrine, found in many decongestants, can sometimes lead to changes in menstrual flow or timing. However, most common cold medications, including antihistamines, are not typically associated with significant disruptions to the menstrual cycle.

The pregnancy tests taken on December 11 and 13, which both returned negative results, are likely accurate, especially if they were taken correctly and at the appropriate time. Home pregnancy tests are designed to detect the hormone hCG (human chorionic gonadotropin) in urine, which is produced shortly after a fertilized egg attaches to the uterine lining. If the tests are negative and her period has not arrived, it may indicate that she is not pregnant. However, it is also possible that she tested too early, especially if her cycle is irregular.

Given that her last menstrual period was from October 31 to November 7 and she has not had a period since, it is advisable for her to consult a healthcare provider. A doctor can perform a blood test for pregnancy, which is more sensitive than home urine tests, and can also evaluate her menstrual irregularities.
In summary, while the medications she has taken may have some effect on her menstrual cycle, the more pressing concern is to rule out pregnancy and understand the underlying causes of her irregular periods. If her period does not arrive soon, or if she continues to experience symptoms that concern her, seeking medical advice is the best course of action. Additionally, maintaining a healthy lifestyle, managing stress, and keeping track of her menstrual cycle can help in understanding her reproductive health better.

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