Miscarriage is the spontaneous loss of an intrauterine pregnancy before 24 weeks gestation. It occurs in approximately 10 – 24% of all clinical pregnancies.1
The major risk factors for miscarriage are increasing maternal age and the number of previous miscarriages.1
Most miscarriages (~80%) are diagnosed under 13 weeks, with the risk of miscarriage decreasing as gestational age increases.
In the first trimester, the most common cause of miscarriage is a chromosomal abnormality (50-60%). Autosomal trisomy is the most common abnormality (e.g. trisomy 16). The most common single chromosomal anomaly is 45X karyotype.
Maternal age is related to aneuploidy risk, with increasing maternal age increasing aneuploidy risk (and therefore increasing the risk of miscarriage).
In the second trimester miscarriage is commonly due to an incompetent cervix (e.g. due to previous cervical surgery) or systemic maternal illness.
A speculum examination should be performed to assess the cervical os, rule out other sources of bleeding (e.g. cervical/vaginal pathology), quantify the bleeding and assess for visible products of conception.
If an ectopic pregnancy is suspected, a bimanual examination should also be performed. Adnexal tenderness or a mass, and cervical motion tenderness, may be present in an ectopic pregnancy.
Relevant laboratory investigations may include:
Full blood count: in patients who have significant blood loss and/or evidence of hypovolaemia
Beta-HCG: provides an indication as to whether the pregnancy is progressing (see below)
Group and save / cross-match: if significant bleeding
Antibody screen: rhesus negative women undergoing a surgical procedure to manage miscarriage will require anti-D rhesus prophylaxis
A transvaginal ultrasound should be performed in any patient presenting in early pregnancy with vaginal bleeding and/or abdominal pain.
The aim of ultrasound scanning is to assess for an intrauterine pregnancy or evidence of an ectopic pregnancy (adnexal pathology or the presence of free fluid in the abdomen).
In addition, the ultrasound can assess fetal viability at that point in time.
If the ultrasound scan is inconclusive for an intrauterine pregnancy (i.e. there is a pregnancy of unknown location), serial beta-HCG measurements are performed. Serum beta-HCG levels should increase by more than 63% in 48 hours in a progressing pregnancy. Ectopic pregnancy is not excluded, although it is unlikely.
Beta-HCG levels that fall by more than 50% in 48 hours indicate a failing pregnancy (potential miscarriage).
Beta-HCG levels that fall by less than 50%, or fail to rise by more than 63%, over 48 hours require clinical review to exclude an ectopic pregnancy.
All patients require an assessment of their haemodynamic status.
Patients who present with significant haemorrhage, and/or evidence of haemodynamic instability, require an ABCDE approach and urgent senior input from the obstetrics & gynaecology team.
A speculum examination should be performed and products of conception should be removed. Products of conception in the cervical os can lead to cervical shock due to vagal stimulation.
Continued bleeding in a haemodynamically unstable patient warrants surgical management.
There are two options for the surgical management of miscarriage:
Manual vacuum aspiration (MVA): can be performed under local anaesthetic on the ward, involves manual suction aspiration of the uterus
Surgical evacuation: usually performed in theatre under general anaesthetic, an electronic suction device is used to remove products of conception
Surgical management should be performed in patients with significant bleeding who have retained products of conception. Surgical management is also used when medical management or expectant management has been unsuccessful.
Rhesus negative patients undergoing surgical management of miscarriage should be given anti-D rhesus prophylaxis.
Medical management involves the use of a prostaglandin agent (misoprostol) to induce uterine contractions and effacement of the cervix.
A pregnancy test should be performed three weeks after medical management. If positive, imaging for retained products of conception will be required.
Expectant management involves waiting for spontaneous passage of the products of conception, without any medical or surgical intervention.
A pregnancy test should be performed three weeks after expectant management providing pain and bleeding settles. If positive, imaging for retained products of conception will be required.
If no bleeding has occurred, or worsening pain or bleeding, women require repeat assessment and alternative management.
Psychological implications of miscarriage
All patients should be offered support following a miscarriage. The Miscarriage Association provides information and a helpline for patients.3
It is important to have a sensitive approach and an opportunity for both the women and her partner, to ask any questions.
Recurrent miscarriage is defined as three or more miscarriages. These patients require a specialist review to assess for an underlying cause of miscarriage.