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Could an Antibiotic Increase Chance of Pregnancy

Published: May 14, 2012
Dear TeenHealthFX,

 

Hi I’m 18 years old and VERY scared I could be pregnant.  I’ve been on the pill about half a year, just recently I’ve been sick and had to take an antibiotic.  I’m still taking my pill at the same time every day but I know you’re not supposed to have unprotected sex taking the pill with an antibiotic as it reduces its efficacy (I don’t know how much though)  well me and my boyfriend knew we had to have sex with a condom so he got one.  When I put it on him I thought it felt a little too lose, but didn’t think too much of it.  When he pulled out before ejaculating he noticed the condom fell off, I found it inside me so I don’t know how much sperm actually got out or when the condom came off.  AGAIN I’m still taking my pill (however also taking an antibiotic) so I’m still afraid this accident could have got my pregnant.  Could this be a big possibility? Could the antibiotic have increased the chances? We are both very scared, but prepared to deal with the consequences of our actions!

Signed: Could an Antibiotic Increase Chance of Pregnancy

Dear Could an Antibiotic Increase Chance of Pregnancy,

 

Whether or not antibiotics can affect the efficacy of birth control pills is not entirely clear. There are two possible ways that certain antibiotics can interfere.

The majority of oral contraceptive pills contain the hormone estrogen that gets processed by specific enzymes in the liver.  There are certain antibiotics, in particular Rifampin and Rifabutin (antibiotics typically used to treat tuberculosis), that may cause the enzymes in your liver to increase the break-down of these hormones and reduce the levels of estrogens in the body thereby lowering the efficacy of birth control pills. This can lead to unwanted pregnancy. For that reason, individuals taking birth control pills should use a second method of birth control when taking these particular antibiotics or other drugs that can increase the break-down of estrogens.  Spotting may be one of the first signs that an antibiotic is interfering with the effectiveness of your birth control pills.

Another way that antibiotics can interfere is by possibly decreasing the re-circulation of estrogens within the body. Although it has not been well proven that unwanted pregnancies can occur through these means, certain antibiotics such as tetracyclines and ampicillins have some better evidence than others. Therefore drug companies always advise to use a backup method when taking antibiotic therapy.

Though the chance of getting pregnant when taking antibiotics while on birth control pills is minimal, you always want to be on the safe side.  Until better data is gathered, people taking birth control pills are recommended to use a second method of birth control while taking these antibiotics (i.e. condoms), which will not only protect from unwanted pregnancy but a sexually transmitted diseases (STD’s) as well. Other categories of medications that may cause a similar interaction with birth control pills include:  Phenobarbital and Carbamazepine (both of which are anti-seizure meds), Griseofulvin (an anti-fungal med), and Topiramate (migraine medication and an anti-seizure med). 

Using a condom can be an effective way to protect against pregnancy as well as STD’s. However it is important that you follow a few basic rules to provide maximum protection. To learn more about the proper use of condoms, checkout TeenHealthFX’s response to “Using Condoms Correctly.”

 

 

If you think that there is a chance that you are pregnant then it would be a good idea to purchase a home pregnancy kit. Home pregnancy tests can be very accurate if used correctly and according to the package instructions. Most home pregnancy tests instructions say to wait until 8 - 11 days after ovulation or after the first day of your missed period.  If you get a positive response you will need to follow up with your doctor or with an Adolescent Health Clinic. They will confirm your pregnancy by using a more accurate blood test. If the test is positive then the medical professionals will help guide you through the next phase. 

 

If you don't have a doctor and live in northern New Jersey, you can call the Adolescent/Young Adult Center for Health in Morristown 973-971-6475 or the Adolescent/Young Adult Center for Health in Summit at 908-522-5757 for an appointment. Outside this area contact a local Adolescent Medicine Specialist, your local teen health center or Planned Parenthood.

 

 

Signed: TeenHealthFX

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