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Becoming Pregnant While on Birth Control

Becoming Pregnant While on Birth Control

What? How could this happen?! Are some of the familiar exclamations from women when they find out they are pregnant on birth control. It can be frustrating, depressing even. Well, it’s more common than you would imagine. Almost half of the over 6 million pregnancies in the United States, every year are whoops babies

While some methods are more effective than others, correct use of contraception is important for effectiveness. Most birth control methods work effectively with ‘perfect use’, meaning the method is always used correctly. Some methods are less effective with ‘typical use’ — not using the method correctly and consistently. Take a look at the effectiveness of the most common types of birth control and how you can lower your chances of a surprise pregnancy.

The Birth Control Pill

If used perfectly, oral contraceptives which contain hormones that stop ovulation, are a great way to prevent pregnancy, with a 99.7% effectiveness rate. With the combined contraceptive also known as ‘the pill’ you have a smaller chance of getting pregnant. The combined pill contains artificial versions of the female hormones, estrogen and progesterone that prevent ovulation, which is when the ovaries release an egg for fertilization. Since most women have busy schedules, a lot of women forget to take the pill every day. Typically reducing its effectiveness to 91%.

Unlike combination birth control pills, the progestogen-only pill also known as the minipill does not contain estrogen. The minipill also has a lower progesterone dose than that in the combination birth control pill. The minipill thickens the cervical mucus and thins the lining of the uterus (endometrium), preventing sperm from reaching the egg. It also suppresses ovulation, though not consistently. Other reasons why your birth control pill may not work include: 

  • If you take antibiotics while on the pill. Every pill packet has a warning label in fine print that says taking antibiotics may lessen the efficacy of the pill. But unfortunately, most people don’t read the fine print.
  • You’re not taking the pills at the same time each day or you miss a day. Birth control pills should be taken at around the same time each day. If you miss your window you should use a backup birth control method for the next 2 days or avoid having sex. Set a daily alarm reminding you to take your pill at the correct time each day.
  • You are vomiting or have diarrhea for more than 48 hours
  • You’re obese. Birth control pill does not work as well in very overweight women.

Long-active reversible contraceptive (LARC) methods

These methods have no user failure.

  • Contraceptive implant/ Nexplanon. This is a small flexible plastic rod that’s placed under the skin in your upper arm by a doctor or nurse. It works by releasing the hormone progestogen into your bloodstream to prevent pregnancy. The implant lasts for 3 years, but can be taken out earlier. It has more than 99% effectiveness with perfect use.
  • Intrauterine system (IUS). An IUS is a small, T-shaped plastic device that’s put into your womb (uterus) by a doctor or nurse. It releases the hormone progesterone to stop you getting pregnant and lasts for 3 to 5 years depending on the brand, but can be taken out earlier. It is more than 99% effective.
  • Intrauterine device (IUD). An IUD, sometimes called ‘coil’ or ‘copper coil’ is a small T-shaped and copper device that’s put into your womb by a doctor or nurse. It works by releasing copper to stop you getting pregnant, and protects against pregnancy for between 5 and 10 years depending on the type but can be taken out at any time. It is worthwhile to note that older types are less effective. It also has more than 99% effectiveness.

Contraceptive Injection

The injection lasts for 8 or 13 weeks, depending on the type. For perfect use it is more than 99% effective, while for typical use it has around 94% effectiveness.

Diaphragms and caps

A contraceptive diaphragm or cap is a circular dome made of thin, soft silicone that’s inserted into the vagina before sex. It covers the cervix so sperm cannot get into the womb to fertilize an egg. This method is 92% to 96% effective when used with spermicide and 71% to 88% without.

Patch and ring

The contraceptive patch is a small sticky patch that releases hormones into your body through your skin to prevent pregnancy. It is more than 99% effective with perfect use, and 91% with typical use. The vaginal ring — a small soft, plastic ring that you place inside your vagina releases a continuous dose of estrogen and progestogen into the bloodstream to prevent pregnancy. It is more than 99% effective when used correctly.


This is the only type of contraceptive that can prevent pregnancy and protect against sexually transmitted infections (STIs). There are two types of condoms: the external condom, worn on the penis and the female condom worn inside the vagina. The external condoms are more effective than the female condoms. But there is still the risk of the condom splitting.

Natural family planning 

Also known as fertility awareness is where a woman monitors and records different fertility signals (cervical secretions and basal body temperature) during her menstrual cycle to work out when she’s likely to get pregnant. If done correctly it is 99% effective.


A permanent method of contraception which included the female sterilization and male vasectomy. This is the most effective method of contraception.

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