Endometriosis, Pregnancy and Accuracy of Home Pregnancy Test Kits


Q: I have stage 1 Endometriosis n am on Microgynon 30 constantly for 3 months at a time, followed by 7 day break allowing for period. The last time I had sex was 4 months ago. on my last break from the pill i did not have a normal period as i usually would, but very light spotting. Also lately I have had strange sensations like popping popcorn in my abdomen and severe mid back pain, different to that of which i suffer with the Endo. I carried out a home pregnancy test around 2 months ago which came up negative. I was wondering what the likelihood of being pregnant and my medication producing a false negative result. I take between 6 - 8 tramamdol a day as well as microgynon n mebeverine. Please help as I am growing increasingly anxious as I would now be around 4 months pregnant if I am and cannot get straight forward answer from my GP. Thank you


A:   First of all, may I just remind you that for contraceptive pills to be effective, perfect use should be done. This means that it should be taken at the same time everyday (e.g. 9 PM everyday). Also, it is best to have back-up contraception (e.g. condoms) if you will have sex on Day 1-5 and Day 16-21 of the pill to prevent pregnancy, if that is what you want. For example, if you have unprotected sex on Day 20 (2nd to the last day) of the pill, there is still a chance of becoming pregnant. The viability (lifespan) of the sperm once it is within the female reproductive organs is ~3-5 days. If an egg will be released on Day 22 (first day without the pill), there is a significant chance of conceiving. The vaginal spotting you had can be a side effect of the pill, which is common. With regards to the pain, it is difficult to say what it is. Would you describe it as throbbing? Or pulsating? It could be Mittelschmerz (irritation of intrabdominal fat when an egg is released from the ovary), gastrointestinal origin, or muscle spasm. If the pain is worsening, immediate attention is necessary. Physical exam and possibly further tests are needed to determine the cause of your abdominal pain.
With regards to the medications you are currently taking, let me brief you with the drug categories in pregnancy. Category A are the drugs that has been proven to be safe in human subjects and therefore, beneficial and safe in all trimesters of pregnancy. Category B are the drugs that has been proven to be safe in animal subjects, but there are conflicting or inadequate studies in human subjects; these are used as 2nd options. Category C are the drugs wherein studies showed adverse reactions in animal subjects and there are inadequate studies in human subjects. Risks vs. Benefits should be weighed before using these drugs. Category D drugs are those with proven harmful effects in human subjects, hence, used only when benefits clearly outweigh the risks. Category X are those wherein animals or human subjects have  shown fetal abnormalities based on data from investigations or marketing experience; the risks involved in use of the drug in pregnancy clearly outweighs benefits. Mebeverine is a category A drug; however Tramadol is in category C and Microgynon is in Category X.  Don’t panic just yet. Do remember that a home pregnancy test kit is not 100% accurate. It is best to do it early in the morning (first morning urine upon waking up) as it is the most concentrated. If you really are anxious to know for sure if you are pregnant or not, an ultrasound will be a better idea. In fact, it is the only test that can confirm or rule out pregnancy. It is also unlikely that your medications interacted with the pregnancy test and produced a false negative result. Usual causes of false negative pregnancy test results are: when it is done too early or too late in pregnancy, when the hormone being detected (usually B-hCG but it also depends on the brand) is either too high or too low, incorrect use or inadequate sample. As mentioned previously, it is better to do an ultrasound to confirm pregnancy. I do hope this helps and I wish you all the best.

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