There are three main causes of bleeding in pregnancy. Find out why bleeding in pregnancy should always be checked out by your maternity carer.

What is bleeding in pregnancy?

Bleeding in pregnancy refers to any vaginal blood loss from the time that pregnancy begins until labour commences.

Causes of bleeding in early pregnancy

Bleeding in early pregnancy – up until 20 weeks – may be associated with miscarriage or threatened miscarriage. In most cases a small amount of blood spotting will settle down and the pregnancy will continue normally. If the bleeding becomes heavy then the chance of a miscarriage increases.

For more information on Miscarriage, please visit our article explaining the causes and care available for miscarriage.

What about bleeding in pregnancy if my blood group is Rhesus negative?

If your blood group is Rhesus D negative, which is the case for approximately 15% of women, then any bleeding in pregnancy will be treated with an injection of Anti D. If the mother is rhesus negative this means that her blood does not possess the Rhesus factor, a protein on red blood cells. If her baby is Rhesus positive then the baby will have the Rhesus factor. If there is any cross over of fetal and maternal blood during pregnancy then the mother’s body will develop antibodies to the Rhesus factor, which it recognises as foreign. This could result in the mother rejecting any subsequent babies which are also Rhesus positive.

By giving Anti D to the mother she is prevented from building up antibodies to the Rhesus factor.

It is necessary to report all bleeding in pregnancy, no matter how minor, in order to receive Anti D within 3 days.

Bleeding in pregnancy after 20 weeks

There are three main causes of bleeding in pregnancy after 20 weeks gestation:

  • Placental abruption
  • Placenta praevia
  • Incidental causes

Placental abruption

This refers to the placenta coming away from the wall of the uterus during pregnancy, prior to the birth of the baby.

Usually the placenta is firmly embedded in the wall of the uterus, with large blood vessels bring nutrients and oxygen to the baby and removing waste products, such as carbon dioxide, and returning them to the mother’s blood supply for her to excrete with her own waste products. The blood supply through the placenta is considerable in order to allow the exchange of substances across the placenta. Therefore, if the placenta is separated, or partially separated, from the wall of the uterus the blood loss can be considerable.

Placental abruption can be caused by:

  • A road traffic accident
  • A fall
  • An attack on the mother, involving punches or kicks to the mother’s abdomen. Unfortunately domestic violence increases during pregnancy. If you experience violence in pregnancy or at any time you can contact the Women’s Refuge at the links below.

If placental abruption occurs there is nothing that anyone can do about it. If a woman reports bleeding in pregnancy – and the placenta is situated normally within the womb (not over the cervical opening at the bottom of the uterus) – then placental abruption will be assumed until it can be proven otherwise.

In the cases of light bleeding the baby’s condition will be monitored via the heart beat (a cardiotocograph, or CTG will be done) and a scan will be arranged to observe the location of the placenta in the womb and any signs of bleeding around the edge of the placenta.

In the cases of heavy bleeding, which is very rare, the maternity staff will:

  • Monitor the mother’s condition to find out whether she has lost a life threatening amount of blood
  • Monitor the baby’s condition to find out whether the baby is distressed (short of oxygen)
  • Arrange emergency delivery of the baby if necessary, via Caesarean section.

Placenta Praevia

Placenta praevia means the placenta is coming first. In these instances the placenta is attached to the wall of the womb next to or over the cervix. It occurs in 0.5% of pregnancies at term.

At anomaly scans at 19-20 weeks gestation many low placentas are detected. As the womb stretches during the next few months of pregnancy the location of the uterus appears further from the cervix. Therefore when ‘low placenta’ is diagnosed at early scans, a repeat scan at 34-36 weeks is planned to check the location of the placenta near term.

If the placenta remains low, a plan for safe management of pregnancy and delivery will be made between the woman, her whanau and the maternity professionals. This may involve hospital admission in case of bleeding and planned Caesarean section.

There are different grades of placenta praevia:

Grade 1 – the placenta is partly in the lower segment of the womb, but does not reach the cervical opening.

Grade 2 – the placenta reaches the cervical opening , but does not cover it

Grade 3 – the placenta covers some of the cervix

Grade 4 – the placenta is located centrally over the cervix.

If the placenta praevia is minor (grades 1 and 2) then the baby may be born vaginally, but this is significant because the muscles in the lower segment are not so effective at contracting to prevent haemorrhage in the third stage of labour.

If the placenta praevia is major (grades 3 and 4) then the baby cannot be born vaginally as the opening to the vagina is covered by placenta. In addition to this, the placenta is attached where there is less muscle to prevent haemorrhage during the third stage of labour. Not only will the mother require a Caesarean section, but she is also at increased risk of haemorrhage.

Incidental causes

Occasionally there is no cause found for bleeding in pregnancy. Sometimes there may be a link with sexual intercourse, sometimes with cervical erosion which is common in women who take the contraceptive pill. After a check up to assess mother and baby’s condition and a scan to confirm that all appears normal, the women is discharged home, with no known cause for the bleed.

On arriving at hospital after a vaginal bleed in pregnancy, expect the following:

  • Assessment of the mother through history taking, blood pressure, pulse, appearance, blood loss (always keep your pads, towels etc).
  • Assessment of the fetus, through history of fetal movements, CTG and scan
  • Insertion of an intravenous line to provide fluid replacement for the mother
  • Blood tests for anaemia and blood group
  • A plan will be made depending upon the amount of blood loss and the condition of mother and baby. This may involve delivery, but most often it is ‘wait to see’ if the blood loss resolves. In most cases it does and you return home after 24 hours of no blood loss.

Many women experience violence in pregnancy and at other times. Domestic violence is never acceptable. For advice and support visit from the women’s refuge in New Zealand contact – www.womensrefuge.org.nz

Useful articles

For more information on Miscarriage, click here

To understand more about the Stages of Labour, visit our informative article.

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Paula Skelton is a qualified NZ nurse and midwife, a midwifery & childbirth educator and the mum of three lovely girls.

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