Ultrasound is the primary imaging modality used in pregnancy.1–4 In the first-trimester, pregnant patients who present with vaginal bleeding or abdominal pain, ultrasound can be used to distinguish ectopic pregnancy from threatened abortion or embryonic demise. The primary goal of emergency sonography of the pelvis in the first trimester is to identify an intrauterine pregnancy, which usually excludes the diagnosis of ectopic pregnancy.5 Secondary objectives are to detect extrauterine signs of an ectopic pregnancy, estimate the viability of an intrauterine pregnancy, clarify gestational age, and characterize other causes of pelvic pain and vaginal bleeding. In addition, sonographic detection of free fluid outside of the pelvis can help emergency physicians expedite the care of a patient with a ruptured ectopic pregnancy.6 Emergency point-of-care sonography is not intended to define the entire spectrum of pelvic pathology in early pregnancy. A follow-up comprehensive pelvic ultrasound examination may be indicated after the initial focused point-of-care examination, the timing of which is dictated by the clinical scenario.
Abdominal or pelvic pain and vaginal bleeding are common complaints during early pregnancy. Challenges to emergency or acute care physicians include making the diagnosis of pregnancy and then using available diagnostic tools to determine the etiology of the patient's complaint.
The development of sensitive pregnancy tests has made a missed diagnosis of early pregnancy unlikely. Modern qualitative urine tests for human chorionic gonadotropin (β-hCG) have a threshold of about 20 IU/L and allow detection of pregnancy as early as 1 week postconception (3 weeks' gestational age). False-negative urine tests may occur when the urine is highly dilute (specific gravity <1.010), and obtaining a quantitative serum β-hCG should be considered in such cases.7
Once pregnancy is recognized in a symptomatic or high-risk patient, complications of early pregnancy, particularly ectopic pregnancy, must be considered. Those patients with pelvic or abdominal pain, vaginal bleeding, dizziness, syncope, or any risk factors for ectopic pregnancy need to have the status of their pregnancy evaluated. The location, viability, and gestational age of the pregnancy are important factors in establishing a diagnosis. Other findings such as free intraperitoneal fluid in the pelvis or a pelvic mass may also impact the patient's management.
Many diagnostic tests can be used to detect complications of early pregnancy. Serum β-hCG and progesterone levels, suction curettage, culdocentesis, and laparoscopy yield some information, but none can identify the entire spectrum of pathology like pelvic sonography. Furthermore, other imaging modalities, like CT and MRI, are not commonly used for detecting complications of early pregnancy.
The hormone β-hCG is produced by the trophoblasts during early pregnancy. Serum β-hCG levels rise exponentially in early pregnancy and can be used as a marker to date normal pregnancies. However, abnormal pregnancies have widely varying β-hCG levels, so a single level cannot differentiate a normal intrauterine pregnancy from an ectopic pregnancy or other abnormality.8