Subchorionic haemorrhage (haematoma): bleeding behind the pregnancy sac

The Chelsea and Westminster NHS trust leaflet describes a subchorionic haematoma (SCH) as bleeding or a build-up of blood between the wall of the uterus and the sac or membranes that protect the developing baby, or, later in pregnancy, underneath the placenta itself. Tommy's describes the pooling of blood in the womb around the sac in which the embryo is developing.

You may hear subchorionic haemorrhage, subchorionic haematoma or intrauterine haematoma used for the same finding. The trust says the cause is unclear and that partial separation of the membranes from the wall of the uterus is thought to be the explanation.

The trust says bleeding can range from spotting to heavy bleeding with clots, usually without pain although some people have mild cramping. Tommy's says symptoms include bleeding and stomach pain. Sometimes there are no symptoms and the haematoma is found incidentally on an ultrasound; occasionally it cannot be seen on scan at all.

If you bleed in early pregnancy you will be offered an ultrasound, which will show the haematoma if it is present, according to the trust. The wider process of an early pregnancy unit visit, including blood tests and a vaginal scan, is described by the RCOG and Tommy's. Any bleeding should be checked, and Tommy's advises contacting your GP or maternity unit.

The trust says SCH is not considered normal but is not unusual, and can occasionally be associated with increased risk of miscarriage. This is more likely if the haematoma is larger, if the person is older, if it is diagnosed earlier in pregnancy, or, later on, if it lies behind the placenta rather than just behind the membranes. If the pregnancy continues there is a small increased risk of early labour or early breaking of the waters, placental abruption and blood-pressure-related problems later, though the trust says evidence for these is limited. Tommy's lists placental abruption, early and late miscarriage and preterm premature rupture of membranes among possible complications and says your healthcare professional will talk through what it means for your care.

These are risks to be aware of, not predictions. The trust is explicit that most pregnancies affected by an SCH progress normally and end in the delivery of a healthy baby.

The trust says no follow-up is required for most women with a viable pregnancy inside the womb. Those who are still bleeding 14 days after the scan, or whose bleeding worsens, should contact the early pregnancy unit. If the haematoma is large compared with the pregnancy sac, the bleeding is moderate to heavy and ongoing, or you have had recurrent miscarriages, monitoring with follow-up scans is often all that is recommended.

The trust says that if you bled after 12 weeks and are rhesus negative you will be offered an anti-D injection, and that progesterone pessaries may be offered, although benefit for SCH itself has not been proven; if you have had a previous miscarriage and bleed in early pregnancy, progesterone pessaries can help improve outcome and will be offered. Treatment decisions are individual, and it is for your clinician to advise whether any of this applies to you.

On activity, the trust advises going about daily life with few changes, says there is no evidence for bed rest, and recommends avoiding strenuous activity or sexual intercourse, with greater risk the larger the haematoma.

The NHS says to call 999 if you are pregnant and bleeding with severe tummy pain, shoulder pain, feeling faint or dizzy, or heavy bleeding that soaks a pad soon after putting it on. The trust leaflet says to go to the nearest A&E if you have significant pain or heavy or worsening bleeding that concerns you. Tommy's says soaking 2 pads in an hour is a reason to seek urgent help, and Tommy's and the NHS both recommend getting any bleeding checked. Local referral routes differ between nations.