Could I be pregnant?

[WorriedGirl87]

Am i pregnant? I am 18 years old and I have been on birth control for over a year. This month I took anti-biotics during the first week and I know that it can make birth control less effective. I have not missed a pill but I have been taking them at different times each night. My boyfriend and I had sex twice this month but also used the withdrawal method each time. It is now one week before my period is due and I have began spotting light brown. Is it possible that this could be a sign of pregnancy?

[Dr. Tamer Fouad]

Hello,

Many things have to be taken into consideration when evaulating abnormal vaginal bleeding in a women taking contraceptive pills.

Assessment of abnormal uterine bleeding associated with hormonal contraception should include history and physical examination (including pelvic examination), assessment of compliance with hormonal contraception, a pregnancy test and a Pap smear. If necessary certain laboratory tests may be required (eg, hemoglobin level, thyroid-stimulating hormone level, prolactin level). Tests for Chlamydia trachomatis and Neisseria gonorrhoeae, can be ordered and a pelvic ultrasonography and endometrial biopsy may be indicated.[1]

The type of pill used (mini-pills have to be taken exactly at the same time with no delays), the antibiotic and timing of sexual intercourse are all very important.

Not all antibiotics decrease the efficacy of contraceptive pills. Those that are said to interact with contraceptive pills include:[2]

Amoxicillin
Ampicillin
Carbamazepine (Tegretol)
Ethosuximide (Zarontin)
Metronidazole (Flagyl)
Phenobarbital
Phenytoin (Dilantin)
Primidone (Mysoline)
Rifampin (Rifadin)
Tetracycline
Troglitazone (Rezulin)
Macrolide antibiotics such as Erythromycin

One common cause of spotting is low progesterone. It’s the hormone progesterone that helps to maintain the uterine lining for pregnancy and when progesterone level drops, the menstrual cycle occurs. In women who are deficient in progesterone, they will see spotting several days to a week before their cycle is due. This can also cause minor infertility and early miscarriage.

Sperm may be contained in the small amount of lubricating fluid a man releases prior to ejaculation. For this reason genital contact or withdrawal method (‘being careful‘) could cause pregnancy if fertile mucus is present at the vaginal entrance.

I recommmend that you take a pregnancy test if you do not get your period. If that is negatve take another test the week after. Please inform your physician at all times. In most cases it turns out to be nothing.

References:
==========
1. Approach to common side effects. In: Wallach M, Grimes DA, Chaney EJ, et al., eds. Modern oral contraception: updates from The Contraception Report. Totowa, N.J.: Emron, 2000:70-6.
2. Hatcher RA, Trussel J, Stewart F, Cates W Jr, Stewart GK, Guest F, et al. Contraceptive technology. 17th rev. ed. New York: Ardent Media, 1998:451-3.

[WorriedGirl87]

I still am not clear on the statistics or chances of me being pregnant, i know all the statistics about withdrawal alone but not withdrawal and the use of birth control. What are my chances?

[Dr. Tamer Fouad]

I couldn't possibly give you an honest assessment without the points I have mentioned above: The type of pill used, the antibiotic and timing of sexual intercourse.

Best regards.

[WorriedGirl87]

The type of pill I have been on for the last four months is Ortho-Tricyclen Lo. Before that I was on regular Ortho Tricyclen for about a year. The name of the anti biotic is Sulfameth/Trimethoprim wich was substituted for Septra DS tablets used for the treatment of a UTI. I think I only used the anti-biotic for about 3-4 days after Jan.1 because i realized that it could decrease the efficacy of the birth control. The timing of intercourse was on Jan. 1 (the last day of my last menses cycle) and on Jan. 8. Both times we used the withdrawal method. Using this information what do you think is my risk of pregnancy?

[Dr. Tamer Fouad]

Sulfameth/Trimethoprim may decrease the effectiveness of contraceptive pills.

However, let me state that there is little convincing evidence to show a systematic interaction between other antibiotics and oral contraceptive steroids. Rifampin (Rifadin) is the only antibiotic that has been shown to decrease estrogen and progestin levels by hepatic enzyme induction and to significantly reduce the efficacy of oral contraceptive pills.[1-4]

However, current studies may not have separately evaluated the minority of women whose metabolism of contraceptive steroids makes them more vulnerable to OC failure.[1-3,5,6] Given the significant consequences of unintended pregnancy, some experts recommend a conservative approach, including patient education and backup forms of birth control.[1,7]

The second sexual encounter occured during the seven days when the antibiotic would potentially decrease the effectiveness of the contraceptive pill. It also occured during the pre-ovulatory relatively infertile phase.

The pre-ovulatory relatively infertile phase is a variable number of infertile days after menstruation. During this phase the follicle is still maturing and the cervical mucus is thick and impenetrable to sperm. The problem with the pre-ovulatory phase is that is variable in length and one cannot know for sure when the fertile phase will start. Remember, the sperm can survive up to 7 days waiting for the ovum to be released. Unprotected sex during the pre-ovulatory period is risky for those wanting to avoid pregnancy.

Now given the fact that you used the withdrawal method as well, I would say your chances are very slim. However, make sure if you don't get your period that you use a pregnancy test starting on the first day of your expected menstrual period.

References:
==========
1. Dickinson BD, Altman RD, Nielson NH, Sterling ML. Drug interactions between oral contraceptives and antibiotics. Obstet Gynecol 2001;98:853–860.
2. DeRossi SS, Hersh EV. Antibiotics and oral contraceptives. Dent Clin N Am 2002;46:653–664.
3. Fazio A. Oral contraceptive drug interactions: important considerations. South Med J 1991;84:997–1002.
4. Zachariasen RD. Loss of oral contraceptive efficacy by concurrent antibiotic administration. Women Health 1994;22:17–26.
5. Neely JL, Abate M, Swinker M, D’Angio R. The effect of doxycycline on serum levels of ethinyl estradiol, norethindrone, and endogenous progesterone. Obstet Gynecol 1991;77:416–420.
6. Orme ML, Back DJ. Factors affecting the enterohepatic circulation of oral contraceptive steroids. Am J Obstet Gynecol 1990;163:2146–2152.
7. Back DJ, Grimmer SF, Orme ML, et al. Evaluation of committee on safety of medicines yellow card reports on oral contraceptive-drug interactions with anticonvulsants and antibiotics. Br J Clin Pharmacol 1988;25:527–532.

[WorriedGirl87]

I am glad that you assess that my chances of pregnancy are very slim, but on the other hand i am very worried about my spotting. It has been a little over 3 days now and I am still spotting light brown and cramping moderately throughout the day. The cramping feels like i am about to start my period but i just continue to spot light brown and that is all. Since I started spotting I have began to take my pill at or about the same time every night in an attempt to stop the spotting, but it has not let up yet. What do you think this is a result of? Could it be implantation bleeding? Or as a result of the anti-biotics? (I have never spotted before on the pill or with this or any previous anti-biotcs). Or could it just be from taking the pill at a different time each nght earlier in the month?? I am scared and nervous because something like this has never happened before. Please let me know what you think it could be...

[Dr. Tamer Fouad]

Hello,

Spotting that occurs about a week before the cycle is due – and only lasts for less than one day – is possibly considered implantation spotting. This happens as a result of the fertilized egg burrowing into the uterine lining. Or another reason for seeing implantation spotting may be due to a slight rise in estrogen and drop in progesterone before the corpus luteum takes over the production of progesterone. The corpus luteum takes over the production when the implanted fertilized egg signals the body that pregnancy has occurred and that the lining must be maintained. Keep in mind that spotting that continues for days is not implantation spotting.

Sometimes early in pregnancy you may have spotting or a brownish discharge at the time your period would normally come. If you have spotting at the time of your normal period rather than your usual amount of flow, and you have had sex without using birth control, you should check a pregnancy test.

Like I said earlier, in women who are deficient in progesterone, they will see spotting several days to a week before their cycle is due.

Another reason spotting may occur could be uterine fibroids, which are fairly harmless, but need to be kept an eye on. Endometriosis, birth control pills are a few other reasons spotting may occur. The most harmful reasons for spotting are possible sexually transmitted diseases and some cancers.

In your case I think its probably a hormonal problem that is related to your irregular intake and / or antibiotic intake. All you have to do is wait for a few more days and check using a pregnancy test. Unfortunately, that's the only way to rule out pregnancy for sure, even if your chances are minimal.

Best regards.

[WorriedGirl87]

My flow picked up a few days ago and turned from light to dark brown and I had to start wearing "lite" tampons and then this morning the dark brown turned to bright red and the flow has picked up a little more. I believe that this is the beginning of my period, which has now happened one day sooner than usual.

If my flow continues to increase to become more like a regular period should i still take a pregnancy test? Or does this now mean that i am definitely NOT pregnant??? Please let me know as soon as possible. Thank You for all your help.

[Dr. Tamer Fouad]

Like I said earlier, most probably you do not have anything. It is still advisable to get a pregnancy test to confirm you are not pregnant.

Best regards.