What abruption is

Tommy's definition is the clearest: "Placental abruption is when some or all of the placenta separates from the wall of the womb during pregnancy." Because the placenta is your baby's oxygen supply, the amount that separates and the speed at which it happens drive everything else.

It sits inside the wider category of antepartum haemorrhage, which Green-top Guideline No. 63 defines as "bleeding from or in to the genital tract, occurring from 24+0 weeks of pregnancy and prior to the birth of the baby". The guideline names abruption and placenta praevia as "the most important causes of APH, although these are not the most common", and reports that APH "complicates 3-5% of pregnancies". Tommy's puts abruption itself at "around 1 in 100 pregnancies".

Why a scan cannot rule it out

This is the single most important clinical fact on this page, and it is stated unambiguously in Green-top Guideline No. 63: "Placental abruption is a clinical diagnosis and there are no sensitive or reliable diagnostic tests available. Ultrasound has limited sensitivity in the identification of retroplacental haemorrhage."

The same section notes that "ultrasound can be used to diagnose placenta praevia but does not exclude abruption", and that "the Kleihauer test is not a sensitive test for diagnosing abruption" - it is performed in rhesus D-negative women to quantify fetomaternal haemorrhage and work out the dose of anti-D immunoglobulin needed.

So if you are told your scan looked normal, that is not the same as being told you have not had an abruption. The assessment that matters is clinical: your symptoms, your abdomen, your observations and your baby's heart rate.

Concealed bleeding, and why the visible loss misleads

The guideline warns that "the amount of blood coming from the introitus may not represent the total blood lost (for example in a concealed placental abruption)", and that blood loss "is often underestimated". It therefore tells clinicians to "assess for signs of clinical shock", and adds that "the presence of fetal compromise or fetal demise is an important indicator of volume depletion".

Tommy's describes the same phenomenon from the other side: "Some people have lower back pain. This may happen if there is a concealed abruption. This is where the blood is behind the placenta, so you may not have any vaginal bleeding." It also notes that "most people with placental abruption have vaginal bleeding. But even though this is the most common symptom, not everyone will have this."

Pain is variable too: "Some feel as if their tummy is bruised, while others describe the pain as very severe or even excruciating." Frequent contractions that do not stop, or a bump that feels tense or hard, are also described. On examination, Green-top Guideline No. 63 says "the tense or 'woody' feel to the uterus on abdominal palpation indicates a significant abruption", whereas "a soft, non-tender uterus may suggest a lower genital tract cause".

How blood loss is graded

These definitions are used to decide urgency, and they are useful for understanding why two people with "some bleeding" get very different responses:

Spotting - "staining, streaking or blood spotting noted on underwear or sanitary protection".
Minor haemorrhage - "blood loss less than 50 ml that has settled".
Major haemorrhage - "blood loss of 50-1000 ml, with no signs of clinical shock".
Massive haemorrhage - "blood loss greater than 1000 ml and/or signs of clinical shock".

Recurrent APH is the term used when there are episodes on more than one occasion, and it changes the monitoring plan in labour.

What increases the risk

Green-top Guideline No. 63 says "the most predictive is abruption in a previous pregnancy", citing a large Norwegian study that "reported a 4.4% incidence of recurrent abruption (adjusted OR 7.8, 95% CI 6.5-9.2)", and notes that "abruption recurs in 19-25% of women who have had two previous pregnancies complicated by abruption".

Other risk factors it lists include pre-eclampsia, fetal growth restriction, non-vertex presentations, polyhydramnios, advanced maternal age, multiparity, low BMI, pregnancy following assisted reproduction, intrauterine infection, premature rupture of membranes and abdominal trauma "both accidental and resulting from domestic violence".

Tommy's separates the evidence by strength. Strong evidence: chronic high blood pressure, pre-eclampsia, cocaine use, intrauterine infection, uterine abnormality, previous abruption, and oligohydramnios. Weaker evidence: previous caesarean, PPROM, not being a first baby, being over 40, and carrying more than one baby. It also states that "smoking can double the risk of having a placental abruption", and that abdominal trauma such as a car accident, serious fall or domestic violence increases risk - with the important instruction that you should be seen after any such injury even if "there does not need to be bleeding or bruising".

How it is managed

Tommy's describes management by gestation and severity. If you are more than 34 weeks, "you may be recommended to give birth straight away"; a vaginal birth may be possible if you and your baby are well and labour is progressing, and a caesarean if either of you is unwell. Under 34 weeks with a small abruption and both of you well, monitoring may continue "to give your baby more time to develop before being born", often as an inpatient, with birth recommended by 37 to 38 weeks to reduce the risk of stillbirth. If you or your baby are very unwell before 34 weeks, birth may be by emergency caesarean.

Green-top Guideline No. 63 adds two points about labour. Tocolysis "is contraindicated in placental abruption". And continuous electronic fetal monitoring is recommended for anyone in labour with active bleeding, for preterm labour after major or recurrent minor APH, and where "there has been any clinical suspicion of an abruption".

NICE guideline NG133 lists placental abruption among the features that may justify planned early birth in pre-eclampsia, which is a reminder that abruption often arrives attached to another condition rather than alone.

Afterwards, and the next pregnancy

Abruption is frightening in a way that follow-up appointments do not always acknowledge. Ask for a debrief: what was found, how much placenta was involved, whether a cause was identified, and what it means next time.

Given the recurrence figures above, a future pregnancy is usually managed as higher risk from the start. Green-top Guideline No. 63 is candid that prevention is thin ground: it found no conclusive evidence of benefit from folic acid supplementation, and "no good data to support a role for antithrombotic therapy (low dose aspirin +/- low molecular weight heparin) in the prevention of abruption in women with thrombophilia". Stopping smoking remains the one modifiable factor with a clear effect size attached to it.

Placental Abruption