Offer women who attend an early pregnancy assessment service (or out-of-hours gynaecology service if the early pregnancy assessment service is not available) a transvaginal ultrasound scan to identify the location of the pregnancy and whether there is a fetal pole and heartbeat. [2012]
Consider a transabdominal ultrasound scan for women with an enlarged uterus or other pelvic pathology, such as fibroids or an ovarian cyst. [2012]
If a transvaginal ultrasound scan is unacceptable to the woman, offer a transabdominal ultrasound scan and explain the limitations of this method of scanning. [2012]
Inform women that the diagnosis of miscarriage using 1 ultrasound scan cannot be guaranteed to be 100% accurate and there is a small chance that the diagnosis may be incorrect, particularly at very early gestational ages. [2012]
When performing an ultrasound scan to determine the viability of an intrauterine pregnancy, first look to identify a fetal heartbeat. If there is no visible heartbeat but there is a visible fetal pole, measure the crown–rump length. Only measure the mean gestational sac diameter if the fetal pole is not visible. [2012]
If the crown–rump length is less than 7.0 mm with a transvaginal ultrasound scan and there is no visible heartbeat, perform a second scan a minimum of 7 days after the first before making a diagnosis. Further scans may be needed before a diagnosis can be made. [2012]
If the crown–rump length is 7.0 mm or more with a transvaginal ultrasound scan and there is no visible heartbeat:
seek a second opinion on the viability of the pregnancy and/or
perform a second scan a minimum of 7 days after the first before making a diagnosis. [2012]
If there is no visible heartbeat when the crown–rump length is measured using a transabdominal ultrasound scan:
record the size of the crown–rump length and
perform a second scan a minimum of 14 days after the first before making a diagnosis. [2012]
If the mean gestational sac diameter is less than 25.0 mm with a transvaginal ultrasound scan and there is no visible fetal pole, perform a second scan a minimum of 7 days after the first before making a diagnosis. Further scans may be needed before a diagnosis can be made. [2012]
If the mean gestational sac diameter is 25.0 mm or more using a transvaginal ultrasound scan and there is no visible fetal pole:
seek a second opinion on the viability of the pregnancy and/or
perform a second scan a minimum of 7 days after the first before making a diagnosis. [2012]
If there is no visible fetal pole and the mean gestational sac diameter is measured using a transabdominal ultrasound scan:
record the size of the mean gestational sac diameter and
perform a second scan a minimum of 14 days after the first before making a diagnosis. [2012]
Do not use gestational age from the last menstrual period alone to determine whether a fetal heartbeat should be visible. [2012]
Inform women that the date of their last menstrual period may not give an accurate representation of gestational age because of variability in the menstrual cycle. [2012]
Inform women what to expect while waiting for a repeat scan and that waiting for a repeat scan has no detrimental effects on the outcome of the pregnancy. [2012]
Give women a 24‑hour contact telephone number so that they can speak to someone with experience of caring for women with early pregnancy complications who understands their needs and can advise on appropriate care. See also recommendation 1.2.1 for details of further information that should be provided. [2012]
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. (See also recommendations on human chorionic gonadotrophin measurements in women with pregnancy of unknown location.) [2012, amended 2019]
When carrying out a transvaginal ultrasound scan in early pregnancy, look for these signs indicating there is a tubal ectopic pregnancy:
an adnexal mass, moving separate to the ovary (sometimes called the 'sliding sign'), comprising a gestational sac containing a yolk sac or
an adnexal mass, moving separately to the ovary, comprising a gestational sac and fetal pole (with or without fetal heartbeat). [2019]
When carrying out a transvaginal ultrasound scan in early pregnancy, look for these signs indicating a high probability of a tubal ectopic pregnancy:
an adnexal mass, moving separately to the ovary (sometimes called the 'sliding sign'), with an empty gestational sac (sometimes described as a 'tubal ring' or 'bagel sign') or
a complex, inhomogeneous adnexal mass, moving separate to the ovary.
If these features are present, take into account other intrauterine and adnexal features on the scan, the woman's clinical presentation and serum hCG levels before making a diagnosis. [2019]
When carrying out a transvaginal ultrasound scan in early pregnancy, look for these signs indicating a possible ectopic pregnancy:
an empty uterus or
a collection of fluid within the uterine cavity (sometimes described as a pseudo-sac; this collection of fluid must be differentiated from an early intrauterine sac, which is identified by the presence of an eccentrically located hypoechoic structure with a double decidual sign [gestational sac surrounded by 2 concentric echogenic rings] in the endometrium).
If these features are present, take into account other intrauterine and adnexal features on the scan, the woman's clinical presentation and serum hCG levels before making a diagnosis. (See also recommendations on human chorionic gonadotrophin measurements in women with pregnancy of unknown location.) [2019]
When carrying out a transabdominal or transvaginal ultrasound scan in early pregnancy, look for a moderate to large amount of free fluid in the peritoneal cavity or Pouch of Douglas, which might represent haemoperitoneum. If this is present, take into account other intrauterine and adnexal features on the scan, the woman's clinical presentation and hCG levels before making a diagnosis. [2019]
When carrying out a transabdominal or transvaginal ultrasound scan during early pregnancy, scan the uterus and adnexae to see if there is a heterotopic pregnancy. [2019]
All ultrasound scans should be performed or directly supervised and reviewed by appropriately qualified healthcare professionals with training in, and experience of, diagnosing ectopic pregnancies. [2012, amended 2019]
There was good evidence that, when seen on ultrasound, the presence of an adnexal mass with features of an early pregnancy (a gestational sac containing a yolk sac or fetal pole, with or without a heartbeat) was a reliable indicator for ectopic pregnancy.
Other features such as a complex inhomogeneous adnexal mass, adnexal mass with an empty gestational sac, empty uterus, a collection of fluid in the uterine cavity or free peritoneal fluid might indicate a suspicion of an ectopic pregnancy, but the evidence showed they are not reliable enough features on their own to diagnose an ectopic pregnancy. The committee used their knowledge and experience to recommend that other scan features, clinical presentation and serum human chorionic gonadotrophin (hCG) levels should therefore be used as well to confirm or rule out the diagnosis of ectopic pregnancy.
Full details of the evidence and the committee's discussion are in evidence review A: diagnostic accuracy of ultrasound features for tubal ectopic pregnancy.
The recommendations will not change the amount of ultrasound scanning that is carried out but will standardise practice across the NHS. By defining the features that should be used to indicate the presence of an ectopic pregnancy, or a suspicion of an ectopic pregnancy (which can then be investigated further), the diagnosis of ectopic pregnancy should be improved and so risks to women will be reduced.
Be aware that women with a pregnancy of unknown location could have an ectopic pregnancy until the location is determined. [2012]
Do not use serum hCG measurements to determine the location of the pregnancy. [2012]
In a woman with a pregnancy of unknown location, place more importance on clinical symptoms than on serum hCG results, and review the woman's condition if any of her symptoms change, regardless of previous results and assessments. [2012]
Use serum hCG measurements only for assessing trophoblastic proliferation to help to determine subsequent management. [2012]
Take 2 serum hCG measurements as near as possible to 48 hours apart (but no earlier) to determine subsequent management of a pregnancy of unknown location. Take further measurements only after review by a senior healthcare professional. [2012]
Regardless of serum hCG levels, give women with a pregnancy of unknown location written information about what to do if they experience any new or worsening symptoms, including details about how to access emergency care 24 hours a day. Advise women to return if there are new symptoms or if existing symptoms worsen. [2012]
For a woman with an increase in serum hCG levels greater than 63% after 48 hours:
Inform her that she is likely to have a developing intrauterine pregnancy (although the possibility of an ectopic pregnancy cannot be excluded).
Offer her a transvaginal ultrasound scan to determine the location of the pregnancy between 7 and 14 days later. Consider an earlier scan for women with a serum hCG level greater than or equal to 1,500 IU/litre.
If a viable intrauterine pregnancy is confirmed, offer her routine antenatal care. See the NICE guideline on antenatal care.
If a viable intrauterine pregnancy is not confirmed, refer her for immediate clinical review by a senior gynaecologist. [2012]
For a woman with a decrease in serum hCG levels greater than 50% after 48 hours:
inform her that the pregnancy is unlikely to continue but that this is not confirmed and
provide her with oral and written information about where she can access support and counselling services; see also recommendation 1.2.1 for details of further information that should be provided
ask her to take a urine pregnancy test 14 days after the second serum hCG test, and explain that:
if the test is negative, no further action is necessary
if the test is positive, she should return to the early pregnancy assessment service for clinical review within 24 hours. [2012]
For a woman with a decrease in serum hCG levels less than 50%, or an increase less than 63%, refer her for clinical review in the early pregnancy assessment service within 24 hours. [2012, amended 2019]
For women with a pregnancy of unknown location, when using serial serum hCG measurements, do not use serum progesterone measurements as an adjunct to diagnose either viable intrauterine pregnancy or ectopic pregnancy. [2012]