Miscarriage is the spontaneous termination of a pregnancy. Early miscarriage is before 12 weeks gestation. Late miscarriage is between 12 and 24 weeks gestation.
There are several definitions to remember relating to miscarriage:
- Missed miscarriage – the fetus is no longer alive, but no symptoms have occurred
- Threatened miscarriage – vaginal bleeding with a closed cervix and a fetus that is alive
- Inevitable miscarriage – vaginal bleeding with an open cervix
- Incomplete miscarriage – retained products of conception remain in the uterus after the miscarriage
- Complete miscarriage – a full miscarriage has occurred, and there are no products of conception left in the uterus
- Anembryonic pregnancy – a gestational sac is present but contains no embryo
A transvaginal ultrasound scan is the investigation of choice for diagnosing a miscarriage.
There are NICE guidelines (2019) and local protocols for diagnosing a miscarriage on ultrasound. Always check local and national guidelines when managing patients.
There are three key features that the sonographer looks for in an early pregnancy. These appear sequentially as the pregnancy develops. As each appears, the previous feature becomes less relevant in assessing the viability of the pregnancy. These features are:
- Mean gestational sac diameter
- Fetal pole and crown-rump length
- Fetal heartbeat
When a fetal heartbeat is visible, the pregnancy is considered viable. A fetal heartbeat is expected once the crown-rump length is 7mm or more.
When the crown-rump length is less than 7mm, without a fetal heartbeat, the scan is repeated after at least one week to ensure a heartbeat develops. When there is a crown-rump length of 7mm or more, without a fetal heartbeat, the scan is repeated after one week before confirming a non-viable pregnancy.
A fetal pole is expected once the mean gestational sac diameter is 25mm or more. When there is a mean gestational sac diameter of 25mm or more, without a fetal pole, the scan is repeated after one week before confirming an anembryonic pregnancy.
Less Than 6 Weeks Gestation
Women with a pregnancy less than 6 weeks’ gestation presenting with bleeding can be managed expectantly provided they have no pain and no other complications or risk factors (e.g. previous ectopic). Expectant management before 6 weeks gestation involves awaiting the miscarriage without investigations or treatment. An ultrasound is unlikely to be helpful this early as the pregnancy will be too small to be seen.
A repeat urine pregnancy test is performed after 7 – 10 days, and if negative, a miscarriage can be confirmed. When bleeding continues, or pain occurs, referral and further investigation is indicated.
More Than 6 Weeks Gestation
The NICE guidelines (2019) suggest referral to an early pregnancy assessment service (EPAU) for women with a positive pregnancy test (more than 6 weeks’ gestation) and bleeding.
The early pregnancy assessment unit will arrange an ultrasound scan. Ultrasound will confirm the location and viability of the pregnancy. It is essential always to consider and exclude an ectopic pregnancy.
There are three options for managing a miscarriage:
- Expectant management (do nothing and await a spontaneous miscarriage)
- Medical management (misoprostol)
- Surgical management
Expectant management is offered first-line for women without risk factors for heavy bleeding or infection. 1 – 2 weeks are given to allow the miscarriage to occur spontaneously. A repeat urine pregnancy test should be performed three weeks after bleeding and pain settle to confirm the miscarriage is complete.
Persistent or worsening bleeding requires further assessment and repeat ultrasound, as this may indicate an incomplete miscarriage and require additional management.
Misoprostol is a prostaglandin analogue, meaning it binds to prostaglandin receptors and activates them. Prostaglandins soften the cervix and stimulate uterine contractions.
Medical management of miscarriage involves using a dose of misoprostol to expedite the process of miscarriage. This can be as a vaginal suppository or an oral dose.
The key side effects of misoprostol are:
- Heavier bleeding
Surgical management can be performed under local or general anaesthetic.
There are two options for surgical management of a miscarriage:
- Manual vacuum aspiration under local anaesthetic as an outpatient
- Electric vacuum aspiration under general anaesthetic
Prostaglandins (misoprostol) are given before surgical management to soften the cervix.
Manual vacuum aspiration involves a local anaesthetic applied to the cervix. A tube attached to a specially designed syringe is inserted through the cervix into the uterus. The person performing the procedure then manually uses the syringe to aspirate contents of the uterus. To consider manual vacuum aspiration, women must find the process acceptable and be below 10 weeks gestation. It is more appropriate for women that have previously given birth (parous women).
Electric vacuum aspiration is the traditional surgical management of miscarriage. It involves a general anaesthetic. The operation is performed through the vagina and cervix without any incisions. The cervix is gradually widened using dilators, and the products of conception are removed through the cervix using an electric-powered vacuum.
Anti-rhesus D prophylaxis is given to rhesus negative women having surgical management of miscarriage.
An incomplete miscarriage occurs when retained products of conception (fetal or placental tissue) remain in the uterus after the miscarriage. Retained products create a risk of infection.
There are two options for treating an incomplete miscarriage:
- Medical management (misoprostol)
- Surgical management (evacuation of retained products of conception)
Evacuation of retained products of conception (ERPC) is a surgical procedure involving a general anaesthetic. The cervix is gradually widened using dilators, and the retained products are manually removed through the cervix using vacuum aspiration and curettage (scraping). A key complication is endometritis (infection of the endometrium) following the procedure.
Last updated August 2020