Here's what happens if you get pregnant on birth control

Yes, you can get pregnant while on birth control. Here’s what you need to know, whether you’re using the pill, an IUD or another method.

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When Alison Smerek found out she was pregnant with her first child 14 years ago, she’d been on the combined birth control pill (which contains both estrogen and progestin) for close to a decade, and had always been very careful about taking it consistently. When Smerek, then 28, peed on a stick and got a positive result, she thought, I don’t know what I’m going to do. To say it was unplanned is to put it mildly. She and her then-boyfriend, Dean, weren’t even living together in their new home yet, and she was just days into a new job when she got confirmation from her doctor that she was expecting. But after that initial shock, she was overjoyed that they were having a baby. Today, Dean, who is now her husband, says that it was fate, and jokes they wouldn’t have gotten off their butts to get life in gear if it hadn’t been for the surprise baby.

Smerek’s story is not unusual. According to a survey of 3,200 women conducted in 2016 by the Society of Gynaecologists and Obstetricians of Canada (SOGC), one in five of them had an unplanned pregnancy. Though many birth control methods are highly effective, it’s not rare for people to get pregnant while using contraception.  Alt text 5 methods of birth control moms love

Indeed, many of the people Dustin Costescu, an OB/GYN at Hamilton’s McMaster University, sees who have an unplanned pregnancy have been using contraception. “Birth control greatly reduces the chance of having an unplanned pregnancy, but it’s not perfect,” he says. “This is a common experience and so women should never feel ashamed for missing their pills or for having a pregnancy while using birth control.” Here’s what you need to know about the risks of getting pregnant while using birth control.

Getting pregnant while on birth control pills

The birth control pill is popular with Canadian women. According to the Canadian Health Measures Survey released by Statistics Canada in 2015, some 16 percent of non-pregnant Canadian women aged 15 to 49 had taken either the combined pill or the progestin-only pill in the month before they were polled. And it is quite effective, though definitely not perfect. Amanda Black, a professor of obstetrics and gynaecology at The Univeristy of Ottawa, notes that both the combined and the progestin-only pill have an eight percent failure rate with typical use. The main reason for failure? People don’t take it consistently. For those taking the combined pill, it’s especially important to take it every day during the first week of your pack, says Costescu. “If you miss any, even a single pill in that first week, there may not be enough estrogen to keep you from ovulating, and then there’s a risk of getting pregnant,” he says, explaining that the lull in hormones during the previous week off already begins the process of making an egg, so missing a pill in the first seven days can trigger ovulation. There’s even less room for error with the progestin-only pill, where being more than three hours late with your dose is a risk for pregnancy.

The pill can also fail because of illness where you are vomiting or have diarrhea, because it might not have had time to be absorbed into your system, before it’s, ahem, expelled. In terms of medications, some anti-seizure medications can affect absorption and interfere with the hormone levels of the pill, says Black. And there is a chance that St. John’s Wort could also affect the pill’s ability to work, she notes.

If you do get pregnant
People who use a combined pill where they take a one-week break usually have what’s called a withdrawal bleed, which is when the body mimics a period because of a hormone drop at the end of a cycle. But the pill can also mask the easiest sign of pregnancy to notice: a missed period.

“Some women taking a birth control pill will continue to have regular withdrawal bleeds, but other women may have very minimal withdrawal bleeding, or they may be taking it continuously because they want to avoid having a monthly withdrawal bleed,” Black explains. So, your first sign might be breast tenderness, nausea, abdominal girth changes or fatigue.

If you suspect you are pregnant, your first step is to take a home pregnancy test, says Black. If the test is positive, stop taking the pill. (Don’t stop before then or you will put yourself at risk of getting pregnant.) The hormones in the pill that you’ve been exposed to so far will not harm the fetus, says Black. Costescu agrees.“Pregnancy is a high sex hormone state, and so it’s very similar to the clinical effects of being on the pill,” he says. “And the placenta actually keeps these hormones from getting to the developing pregnancy, anyway. They’re filtered out.”

Getting pregnant with an IUD

IUDs are a very effective method of birth control, says Costescu. The copper IUD’s failure rate is a mere 0.8 percent, while a hormonal IUD has a failure rate of just 0.2 percent. A copper IUD is immediately effective when placed, and the hormonal type is effective within five days after being placed, he explains. And, since you don’t have to do anything after it’s in place, and you’ve had a follow-up to make sure it was inserted properly, there’s no chance for user error.

The one risk is that over the five-year life of your IUD, there is a three to five percent chance it may be expelled by your body. “If someone does notice they suddenly have heavy bleeding with clots with an IUD inside, that could be a sign that the IUD’s been expelled,” Black explains. If this happens, do a string check to make sure the IUD is still in place; if you can’t find the string, make an appointment with your health-care provider so they can make sure everything is where it should be and, in the meantime, use backup birth control, such as condoms.

If you do get pregnant
It may be quite rare, but some people do become pregnant with an IUD. For those who use a copper IUD, the first sign of pregnancy would still likely be a missed period. But many women on hormonal IUDs either have no period or have a very light one, which can make it trickier to use as a gauge. For those women, sudden breast tenderness and nausea might be the first clues that they’re pregnant. But, if you just got your IUD, don’t assume that pregnancy is necessarily to blame for these symptoms. Costescu notes that within the first three months of a hormonal IUD placement it’s possible to feel breast tenderness, mild nausea and some pelvic cramping.

If you suspect you’re pregnant, take a home pregnancy test. If it’s positive, it’s important to see a health-care provider as soon as possible to get an ultrasound. It’s an urgent matter because if you get pregnant with an IUD there is a higher chance that it will be an ectopic pregnancy, which means the embryo has implanted in one of your fallopian tubes rather than in your uterus, which can be dangerous, and needs to be treated right away.

If it’s not ectopic and you want to continue the pregnancy, your health-care provider will likely recommend you have the IUD removed if the strings are visible, since a pregnancy with an IUD in place is slightly higher risk says Costescu.

“Although many pregnancies will go on to term without difficulty, there is a higher risk of pre-term birth and of premature breaking of the waters,” he explains. Black adds you can rest assured that an IUD will not cause fetal abnormalities.

There is a small risk of miscarriage when an IUD is removed, but Costescu says it’s hard to put a number to that since there aren’t studies and many early pregnancies don’t go on to be viable.

If your doctor can’t find the strings, the IUD must stay put, and you will be monitored with ultrasounds throughout your pregnancy to make sure that all is well. For example, your health-care provider will keep eye on the IUD in relation to how close it is to the amniotic sac, as the device could rupture this.

Getting pregnant with the patch, ring or shot

There are a few more options when it comes to birth control, and these include the patch, the vaginal ring and the Depo-Provera shot. Black says the failure rate for typical use of the patch and the ring is the same as the pill: eight percent. The Depo-Provera shot has a failure rate of just six percent with typical use.

With all three types of contraception, adherence is the biggest risk factor. They need to be used as directed to work effectively. Costescu says with the patch, which you replace once a week (think of it like a bandage), one issue is that it may accidentally fall off. With the ring, he explains that replacing it on time (users self-insert a new ring in their vagina once a month) is key. And it can only be removed for short periods of time if you want it to remain effective. “Some women choose to remove the NuvaRing when they’re sexually active, and we recommend that it only be removed for up to three hours; so, it can’t be taken out, for instance, for an overnight date,” he says.

Black adds that the same medications that make the pill less effective would have a similar effect on the patch and ring.

With Depo-Provera shots, Costescu notes, you must visit a health-care provider every three months to get the shot. He also says that the shot may be a good option if you’re on anti-seizure medication, as the high dose of hormones that come with this type of birth control means those medications may not interfere with its effectiveness.

If you do get pregnant
With the patch and ring, you would be getting withdrawal bleeding every month, so a key sign that you’re pregnant would be a missed period.

If you suspect you’re pregnant, the first step is to take a home pregnancy test. If the results are positive, then make an appointment with your health-care provider. Don’t stop using your birth control method until you’ve gotten a positive result.

But with the Depo-Provera shot, women don’t get their period every month. It is great from a pregnancy prevention point of view, says Cotescu, but, “when people conceive on it, because they are expecting not to have a period it’s quite common that they get diagnosed later in the pregnancy,” he explains. So, he recommends having a low threshold when it comes to pregnancy testing if you think you might be pregnant while on this form of birth control.

Thankfully, none of these types of contraception will harm a developing fetus, since the natural hormonal state you’re in while pregnant is so similar to the one you’re in while on these forms of birth control, he says.

Read more: 
What happens after you go off the birth control pill?
Everything you need to know about birth control 

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