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What is a Pregnancy of Unknown Location ?

Almost all pregnancies implant in the uterus or womb, where they can grow safely and carry to term if desired.  These are called “intra-uterine pregnancies”.  Once a pregnancy grows large enough, it can be seen on an ultrasound.  This happens by 5 weeks’ gestation for ultrasounds done through the vagina (internal or ‘vaginal’ ultrasounds) and 7 weeks’ gestation for ultrasounds done through the belly (abdominal ultrasounds). Once a pregnancy can be seen inside the uterus, we know it will grow safely without endangering the woman’s life, and that it will respond to the abortions performed in clinics like Cabbagetown Women’s Clinic (CWC).  Very rarely, pregnancies can implant outside of the uterus, where they present danger to the pregnant woman; these are called Ectopic pregnancies.


Ectopic pregnancies have implanted outside of the uterus (most of the time in a fallopian tube but they can implant in other areas too like around the ovaries, for example).  These pregnancies will never be able to grow to term and, once large enough, can cause explosion of the tube (called a ‘ruptured ectopic pregnancy’) and internal bleeding.  Ruptured ectopic pregnancies are very rare, but these are the most common cause of death in the first trimester and account for 4% (1out of 25) of all pregnancy deaths in the US.  It is important to diagnose an ectopic pregnancy as soon as possible and treat it appropriately to save the pregnant patient’s life.  An ectopic pregnancy needs special treatment with injection or a specialized surgery.  Ultrasound is used by some abortion providers to locate a pregnancy and, hopefully, ensure that more specialized care is not needed.


If an ultrasound shows a pregnancy in the correct spot (i.e. inside the womb), the chances of an ectopic pregnancy is almost zero (1/50 000 approximately).  Many abortion providers do a quick ultrasound and note when a normal pregnancy has been seen.  Then we know that the patient is safe and that the abortion will most likely work.  When we do an ultrasound and the uterus has no visible pregnancy, we call this situation a “Pregnancy of Unknown Location” or PUL for short.  A PUL means the situation is one of the following 3 possibilities.


  •  Early intra-uterine pregnancy that is growing


This is the most common possibility when a pregnancy cannot be seen with an ultrasound.  A pregnancy less than 5 weeks’ gestation can be invisible even on a trans- vaginal ultrasound.  Because in Canada, we have good access to technology for monitoring menstrual cycles, to pregnancy tests, and to pregnancy management such as abortion, many pregnant patients know they are pregnant before reaching 5 weeks gestation.  In this case, the woman is pregnant, the pregnancy is NOT in a dangerous location, but it is still invisible to ultrasound.


  • Spontaneous miscarriage has occurred


One out of every 4 to 5 pregnancies will end in the first trimester (i.e. the first 12 to 14 weeks of pregnancy).  This is usually due to the sperm and egg having combined in an abnormal way, which causes genetic problems in the developing embryo.  These embryos (the fetus at the very early days after getting pregnant is called an embryo) would never survive or would produce very sick term babies.  Thankfully, female bodies have evolved to detect these abnormal pregnancies very early, and stop them from growing.  An early miscarriage will ensue which, in very very early pregnancy, can occur even without any cramping or bleeding.  After the pregnancy ends, it can take up to 6 weeks for the urine pregnancy test to return to negative.  In this scenario, the pregnant patient has a positive pregnancy test, there is no visible pregnancy in the womb and this is because the pregnancy has already been expelled or absorbed.  This is the second most common reason to have a PUL.


  • Ectopic pregnancy


A rare cause of PUL is ectopic pregnancy (explained above), where there IS a growing pregnancy which cannot be seen in the uterus because it isn’t there.  It is outside of the uterus.  Ectopic pregnancies account for less than 0.5% of pregnant women.  When ectopic pregnancies are small, they are not dangerous, and the goal of medical care is to diagnose them before they grown large enough to become dangerous.  This is why ectopic pregnancies are diagnosed earlier in women who present to an abortion clinic (because their pregnancies are being monitored earlier to ensure their abortion can be done safely).


FYI… this is medicine.. the list of possibilities in the PUL scenario does not end there.  There are always more rare situations that the doctor is trained to keep in mind (but I’ll leave these to your capable medical providers to explain further).


How do we keep patients safe when they have a PUL?


As explained above, most patients with PULs are NOT having ectopic pregnancies.  If they want an abortion right away (i,e. rather than waiting 1-3 weeks for their pregnancies to grow big enough to be seen on ultrasound or to rule/out a miscarriage), they can have an abortion.  At CWC we keep our patients safe by:


  1. doing a blood level of their pregnancy hormones (which should indicate that the pregnancy is early enough that not seeing it is normal)

  2. doing a second blood level of their pregnancy hormone after the abortion to ensure that it is decreasing.  If the hormone level is decreased by more than half within 1 week (or more than 80% at 7-14 days) it means the pregnancy is no longer continuing. It has either already spontaneously aborted or, more likely, it has responded to the abortion.  As mentioned above, if an abortion worked (pill or surgical abortion) the pregnancy was most likely inside the uterus.

  3. Finally, we do a pregnancy hormone level at 4 weeks after the abortion, to make sure that there is NO MORE detectable pregnancy hormone in the blood.  When there is no more pregnancy hormone detectable, then we can rest assured that there is no more pregnancy (ectopic or otherwise).


During this time, we teach our patients the signs and symptoms that should prompt going to the emergency room (ER).  These are individualized to the pregnant patient’s symptoms at the time of assessment at CWC.  In general however, if you have a positive pregnancy test, are not yet sure of the location of the pregnancy, and are experiencing abdominal pain, vaginal bleeding, feeling faint or fainting, you should go to ER where they can check blood levels and ultrasound testing to ensure you’re safe. Also, if you have an intra-uterine device (IUD) and a positive pregnancy test, you also need an ultrasound to locate the pregnancy right away (it can be done safely outside of ER if you have no pain or bleeding and are feeling well).




N.B. CWC recognizes that not all of our patients are gendered female. Very rarely, there are pregnancies in the uteruses of trans-men and we provide safe, respectful services to these patients. We use words such as females to denote biological females (a term which includes trans-men).

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