Spotting and Bleeding during Pregnancy

Written by

Rob Buist

Published on


Some vaginal bleeding – including spotting – is common in pregnancy and in most situations we don’t find a cause or the cause is completely benign and not threatening to your health or that of your baby. Having said that bleeding or spotting should never be assumed to be normal and it is a symptom that ALWAYS warrants a clinical assessment and sometimes further investigations such as an ultrasound.

We usually divide bleeding in pregnancy into two groups:

  • Bleeding that arises from the lower genital tract (the vulva, the vagina or the cervix), and
  • Bleeding that arises from within the uterus.

And then we think of the causes of bleeding in relation to the trimesters of pregnancy.

Lower Genital Causes of Bleeding

Anything that can affect the lower genital tract when you are not pregnant can affect you during pregnancy. In addition pregnancy causes a much greater flow of blood to your cervix so that organ is more likely to bleed during pregnancy. So bleeding after sexual intercourse is more common in pregnancy simply because the cervix has more blood vessels on it and these are more likely to bleed if they have been, er, bumped. 

Some women have perfectly benign things like polyps on their cervix that can bleed during pregnancy. Unfortunately a very small number of women have more serious conditions like abnormal cells on their cervix or even early cervical cancers. This is why if you do experience bleeding in your pregnancy your Doctor will – quite correctly – insert a speculum into your vagina and visually check your cervix. This procedure cannot harm your baby.

This is also why you should keep yourself up to date with your PAP smears.

Bleeding in the First Trimester

Women who experience bleeding in the first trimester understandably worry about the possibility of a Miscarriage occurring. Fortunately most first trimester bleeding does not indicate a miscarriage but it is important to check your baby’s welfare with an ultrasound at the earliest opportunity if this worrying symptom occurs. Usually the bleeding is caused by one of your blood vessels within your uterus being “exposed” as the uterus expands during the first trimester. As long as this blood vessel is not underneath the placenta it usually causes no harm to your baby. Indeed sometimes the ultrasound people can even see a little blood inside your uterus – this is called a sub chorionic or extra membranous haematoma and the vast majority of these haematomas resolve without harming your baby.

Tragically sometimes bleeding in the first trimester is the beginning of a miscarriage – one of the most miserable experiences you can suffer. It is really important to remember though that:

  • Miscarriages are very common – depending upon your age somewhere between 20 and 30 percent of pregnancies end in a miscarriage, and
  • In the OVERWHELMING majority of situations a miscarriage is unavoidable, unpreventable and there is nothing you, God or your caregivers could have done to prevent it – and NOTHING you did caused it. The very great majority of miscarriages are caused by a lethal chromosomal abnormality – usually a Trisomy or Triploidy – in the baby that was determined at the moment of conception. 

We also must not forget ectopic, or tubal, pregnancies. A pregnancy implanting in the fallopian tube can cause bleeding although pelvic pain usually accompanies the bleeding. Ectopic pregnancies can very rarely rupture and cause internal bleeding so the combination of bleeding and significant pelvic pain is an ectopic pregnancy until proved otherwise so it is important that you seek medical attention urgently – even by attending the Emergency Department if this condition is a possibility.

Bleeding in the Second and Third Trimesters

There are a couple of potentially serious conditions that can cause bleeding in the latter stages of pregnancy although – again – most episodes of bleeding are inconsequential (but must be checked out). The specific conditions that can be concerning are:

  • Placenta Praevia. This is where the placenta has implanted in the lower part of the uterus such that is it close to, or covers the cervix. These days the possibility of a Praevia is usually picked up at your 19(ish) week “morphology” ultrasound scan where the ultrasound people check how close (or otherwise) your placenta is to your cervix. Now a low placenta at your morphology scan does not necessarily mean you have Placenta Praevia – approximately 90 percent of low placentas at 19 weeks move away from the cervix during the second half of pregnancy in order to allow a vaginal birth. 
  • Placental Abruption. This is a rare but potentially catastrophic complication in which part or – God forbid – the entire placenta simply separates from the wall of the uterus. The blood vessels that had been supplying the placenta continue to flow and cause vginal bleeding that can be severe. Large placental abruptions usually necessitate urgent delivery of your baby, often by emergency caesarean section. Placental Abruptions are more common in pregnancies complicated by high blood pressure (including Preeclampsia) or where there are concerns about your placenta’s functioning – most commonly if you have a Small For Gestational Age baby on board.

Now of course the majority of episodes of spotting or bleeding in the second and third trimesters are not due to Placenta Praevia or Abruptions but – again, and at risk of being repetitive – they should be checked out promptly by your caregivers.

A couple of other things about bleeding in pregnancy

As your baby’s arrival nears your cervix begins to change in preparation for the birth. It softens, thins and can even begin to dilate without you experiencing painful contractions. Sometime – not always – this process results in the loss of your cervical mucus plug (it really does look like mucus). We also call this loss your “show”. Now remember I said the cervix has many blood vessels on it when you are pregnant – so your “show” often includes some blood. Usually this is old brown blood but sometimes it can appear fresh. As long as the blood is mixed with mucus this is not concerning unless you experience ongoing fresh bleeding with or without significant pain. Again if you are unsure you should contact your Caregiver.  

The final issue about bleeding in pregnancy is your Blood Group. We are all either Blood Group A, B, O or AB. These are our most important (of many) blood groups. Second in line is your Rhesus, or Rh, Factor (this has something to do with Rhesus Monkeys but I can’t recall why). You can only be Rh Positive or Negative (and you must be one or the other). If you are Rh Negative and your partner (the person who – er – knocked you up) is Rh Positive there is a 75 percent (trust me) chance your baby is Rh Positive. If this is the case and your baby’s blood cells get into your circulation then you can mount a harmful immune response against your baby AND future babies. Common events that cause vaginal bleeding can also cause your baby’ blood to enter your circulation so we commonly give Rh Negative women an injection called Anti D in order to prevent future problems. 

Accordingly it is important that you know your blood group and if you are Rh Negative.