Written by: Caroline Meyer

Spotting blood while you are pregnant can be very frightening. While most causes can be quite innocuous, some vaginal bleeding can be quite dangerous. It is important to contract your care giver if you note any bleeding during your pregnancy. 

During the first trimester, vaginal bleeding can occur from light spotting to extremely heavy bleeding, including large clots. Vaginal bleeding is not uncommon in the first trimester, with around 30% of women experiencing some bleeding during this period. Vaginal bleeding in the second and third trimester is usually related to different causes than that experienced in the first trimester. Any bleeding after week 28 should be treated as an emergency whether or not it includes pain and even if the bleeding appears to be quite mild.   


First trimester bleeding can be caused by a variety of factors. Implantation bleeding can happen then the fertilized egg implants in to the wall of the uterus around the time you would normally have your period. This type of bleeding is usually lighter than your menstrual period and often does not last long. Bleeding can increase the risk of a miscarriage during the early stages of pregnancy as well. In around 2% of pregnancies, the bleeding is caused from an ectopic pregnancy. This is when the foetus implants outside of the uterus and seldom results in a viable pregnancy. An ectopic pregnancy can also be life threatening in some cases. If you experience period like bleeding at any point in the first trimester, you should call your doctor for an evaluation.  

Implantation bleeding usually consists of a small amount of spotting and can present like a very mild period. This is usually no call for concern and often leads to a date of conception being miscalculated at the start.  A threatened miscarriage usually includes cramping along with the bleeding. This can often be caused by an infection such as a UTI, dehydration, certain medications and drugs and physical trauma but occasionally for no apparent reason. In this instance, the foetus has not aborted and remains in the uterus. A completed miscarriage involves cramping and bleeding but an ultrasound confirms that there is no longer a foetus within the uterine space. This is the most common cause of first trimester bleeding and the result is that there is no viable pregnancy. An incomplete miscarriage is when the cervix has opened and you are passing clots, blood and even tissue but not everything has passed out. This can result in an infection and a dilation and curettage may be recommended.  

Blighted Ovum:  This is also known as embryonic failure. This is when the embryo does not develop properly in the correct location even though the ultrasound may show an intrauterine pregnancy. This can result from an abnormal foetus.   

Ectopic Pregnancy: This is when the fertilized egg implants outside of the uterus, usually in the fallopian tubes (tubal pregnancy). This can cause the fallopian tube to rupture and cause bleeding which can be life threatening. Symptoms include bleeding, pain and often dizziness. These are usually discovered before 10 weeks due to the pain they cause. This occurs in around 3% of pregnancies and will result in surgery to remove the foetus which is not viable in this position. Some of the risk factors include prior ectopic pregnancies, previous pelvic inflammatory disease, a history if infertility, Fallopian tube ligation or surgery, smoking, douching daily or having an intrauterine birth control device in place. Around 50% of ectopic pregnancies are in women who do not have any risk factors.  

Molar Pregnancy: This is called gestational trophoblastic disease and is when there is abnormal tissue inside the uterus and not a foetus. This is not life threatening and is generally a non-cancerous tumour that occurs due to pregnancy hormones. There are rare cases of the tissue being malignant and it can also invade the uterine wall and possibly spread further through the body. This may result in treatment by an oncologist.  

Post-coital bleeding is fairly normal during pregnancy and can be seen after sexual intercourse. It is usually nothing to be concerned about.  There may be other reasons for bleeding unrelated to the pregnancy such as an infection or a tear in the vaginal wall or other trauma within the vagina.  


Bleeding later in the pregnancy can be due to an abnormal cervix or vagina or problems with the placenta.   

Placenta Previa: This is a condition where the placenta, which connects your baby to your womb, covers the cervical opening, partially or completely. Bleeding can occur when the cervix thins and dilates and blood vessels from the placenta end up being stretched and rupture. This can be quite serious and is the cause of around 20% of late pregnancy bleeding. Risk factors include previous instances of placenta Previa, multiple pregnancies and prior caesarean deliveries.  

Placental Abruption:  When the placenta pulls away from the wall of the uterus prematurely and results in blood collecting in the space between the uterus and the placenta, this is known as placental abruption. This happens in 0.5% of pregnancies and the cause is not known. Risk factors include cocaine and tobacco use, trauma, high blood pressure and previous abruptions.  

Foetal Vessel Rupture:  This is also very rare, occurring in only 1 of every 5000 pregnancies. This is when the baby’s blood vessels are attached to the membranes and not the placenta. The baby’s blood vessels can pass over the birth canal entrance. This is known as vasa Previa.  

Uterine Rupture:  This is a very rare occurrence and is when the uterus splits and expels the baby fully or partially into to the abdomen. This is extremely dangerous to both the baby and the mother. About 40% of women who experience this have had previous surgery on the uterus such as a Caesarean birth. Other risk factors include trauma, more than 4 previous pregnancies, baby in an abnormal position, excessive use of Oxytocin, forceps delivery, baby’s shoulder being caught on the pelvic bone during the process of labour.  

Other reasons for late pregnancy bleeding include lesions or injury to the vagina or cervix such as cancer, polyps and varicose veins. Another very rare cause is an inherited bleeding problem such as haemophilia. If you have any bleeding conditions, you should advise your doctor at the start of your pregnancy.  


If you find that you are bleeding and you suspect you may be pregnant, it is important to note the type and amount of bleeding so that you can advise your doctor. Take note of clots, tissue and how many pads were used. If you pass any tissue, it should be saved for further examination by your doctor.  

If you experience any other symptoms such an intense thirst, dizziness, fatigue or fainting, this could indicate severe blood loss. Your pulse rate may increase and speed up further upon standing. You may find dizziness also increases when standing. Advise your doctor of these factors and ensure you get immediate assistance. 


If you experience bleeding at any time during pregnancy you should advise your doctor or midwife. Relax as much as possible until you have been examined by your care giver and been advised on possible treatment. You cannot stop the bleeding on your own and should get in contact with your doctor as soon as possible. Stay hydrated and do not do anything strenuous until cleared by your carer. Do not use tampons or a douche. Keep an accurate count of pads used. Bleeding should not be considered normal and your healthcare professional should be consulted if you have vaginal bleeding at any time during your pregnancy. If there are added symptoms and the bleeding is fairly heavy or it is past your first trimester, go to the hospital emergency room for immediate treatment.