Investigations
1st investigations to order
trans-vaginal ultrasound scan
Test
Differentiates between different stages and types of miscarriage.
Specific, fairly prognostic, and would exclude other differential diagnoses of miscarriage.
According to the UK National Institute for Health and Care Excellence guideline, a miscarriage should be considered when trans-vaginal ultrasound reveals a gestational sac with mean diameter ≥25 mm with no visible yolk sac or fetal pole.[69] It is also likely when the crown-rump length of the embryo measures 7 mm or more, with no obvious fetal heart activity.[69][70] A study designed to validate the performance of these cut-off values found that they are not too conservative, but do not take into account gestational age. No advice exists on how to relate gestational age to scan findings and a possible diagnosis of miscarriage.[71]
Guidance from the American College of Obstetricians and Gynecologists advises that an embryo should be visible by transvaginal ultrasonography with a mean gestational sac diameter ≥25 mm. Cardiac motion should be observed when the embryo is ≥7 mm in length. If an embryo less than 7 mm in length is seen without cardiac activity, a subsequent ultrasound examination at a later time may be needed to assess the presence or absence of cardiac activity.[72]
If there is any uncertainty about the viability of a pregnancy, conservative management and ultrasound performed a minimum of 7 days later are recommended, given the real risk of inadvertent evacuation of a desired pregnancy. When diagnosing complete miscarriage on an ultrasound scan, in the absence of a previous scan confirming an intrauterine pregnancy, always be aware of the possibility of a pregnancy of unknown location. Advise these women to return for follow‑up (for example, hCG levels, ultrasound scans) until a definitive diagnosis is obtained.[69]
Result
confirms viability of pregnancy
serum beta hCG titres
Test
Order if uncertain about miscarriage status.
A drop of >50% in 48 hours is suggestive of a failing pregnancy.
A rise in serum hCG of more than 50% over a 48 hour period is suggestive of possible ongoing pregnancy.
Guidelines from the UK National Institute for Health and Care Excellence recommend that women with a decrease of 50%, or an increase of less than 63% in serum hCG concentration should be referred for clinical review in the early pregnancy assessment service within 24 hours.[69]
May be positive up to 21 days after a complete miscarriage.
A combined assay of serum beta hCG and serum progesterone has been found to have a predictive value of 85.7% for inevitable pregnancy loss.[73] If validated in larger clinical trials, this tool may be useful in triaging patients, planning follow-up, and patient counselling.
Result
falling titres indicate a failing pregnancy
Investigations to consider
transabdominal ultrasound scan
Test
Consider for women with an enlarged uterus or other pelvic pathology (e.g., fibroids or an ovarian cyst) above 8 weeks of gestation.
May also be offered to women for whom a transvaginal ultrasound scan is not acceptable, with an explanation of its limitations.
In the UK, the National Institute for Health and Care Excellence recommends that if there is no visible heartbeat on transabdominal ultrasound scan, then the crown-rump length needs to be recorded and a second scan should be performed a minimum of 14 days after the first scan before making a diagnosis.[69]
Result
confirms viability of pregnancy
serum progesterone
Test
Can be ordered if ultrasound findings are inconclusive in a symptomatic patient.
A single serum progesterone titre ranging between 3.2 and 6.0 ng/mL predicts a non-viable pregnancy with a pooled sensitivity of 74.5% and a specificity of 98.4%.[74]
Result
low titres indicate a non-viable pregnancy
urine pregnancy test
Test
Confirms pregnancy, although false negative tests, depending on kit used, are known.
Result
positive
FBC
Test
May indicate degree of blood loss and probable need to transfuse.
Result
low or normal haemoglobin
rhesus blood group
Test
Indicates the need for anti-D immunoglobulin administration.
Result
identifies Rh-negative blood group, if present, in mother
lupus anticoagulant/anticardiolipin antibodies
Test
Consider in recurrent miscarriages.
Presence of anticardiolipin antibodies carries a 3- to 9-fold greater risk of fetal loss in low-risk pregnancies.[42]
Women with a history of at least 3 prior miscarriages and no abnormality other than the presence of antiphospholipid antibodies are likely to have a future miscarriage.
Result
identifies antiphospholipid syndrome
pelvic ultrasound
Test
Congenital malformations can result in early miscarriage depending on the severity and presence of associated chromosomal, vascular, or endocrine pathology.[37]
Acquired structural distortion with large sub-mucous fibroids may also result in pregnancy loss.
Result
congenital or acquired uterine structural abnormalities; polycystic ovarian syndrome
cytogenetic analysis on products of conception
Test
Consider in third and subsequent consecutive miscarriages.[3]
Result
chromosomal/genetic abnormalities
parental karyotype
Test
Consider in recurrent miscarriages when testing of products of conception reports an unbalanced structural chromosomal abnormality.[3]
Result
chromosomal/genetic abnormalities
Use of this content is subject to our disclaimer