In this patient, the first priority is to rule out an ectopic pregnancy. The other possible diagnoses include a threatened miscarriage or early pregnancy failure. She is hemodynamically stable and does not show signs of hemoperitoneum such as abdominal distension, absence of bowel sounds or shoulder tip pain, which might suggest a ruptured ectopic pregnancy. In addition, the absence of cervical motion tenderness, adnexal tenderness and adnexal masses make an ectopic pregnancy less likely, but still do not exclude this diagnosis. Her vaginal examination shows that the cervical os is open. While this is more in favor of an early pregnancy failure, it should be kept in mind that any condition causing pregnancy related bleeding may cause the os to open. Her pelvic ultrasound scan shows an intrauterine gestational sac without fetal cardiac activity, thus establishing the diagnosis to be an early pregnancy failure, i.e. an inevitable miscarriage. She may be managed expectantly or with medical expulsive therapy. As she is Rhesus negative, anti-D immunoglobulin should be administered to prevent sensitization. Antibiotics are not indicated in uncomplicated early pregnancy failure, while methotrexate is used in the treatment of ectopic pregnancy, and is not indicated in this patient.
First trimester bleeding occurs in up to 20% of all pregnancies. Around half of these will end in a miscarriage. Obstetric causes for first trimester bleeding include ectopic pregnancy, threatened miscarriage (where the pregnancy is still viable) and early pregnancy failure. Non obstetric causes are uncommon and include cervicitis, vaginitis, trauma, cervical cancer or polyps. The first priority in these patients is exclusion of an ectopic pregnancy, which is a gynecological emergency. If the patient is hemodynamically unstable or if signs of hemoperitoneum such as abdominal distension, absent bowel sounds and shoulder tip pain are present, a ruptured ectopic pregnancy should be considered and emergency surgery initiated. In those patients who are hemodynamically stable, a focused history and examination may yield further clues. In particular, the presence of cervical motion tenderness, adnexal tenderness or an adnexal mass is suggestive of an ectopic pregnancy, while passage of products of conception or presence of cervical dilation is suggestive of a miscarriage. The next step is to perform a pelvic ultrasound scan. An extrauterine embryo with cardiac activity may be seen in 15% to 20% of patients with ectopic pregnancy and is diagnostic of this condition. In addition, the presence of free pelvic fluid, a tubal ring or a complex adnexal mass is highly suggestive (but not diagnostic) of ectopic pregnancy. Conversely, visualization of an intrauterine gestational sac is suggestive of an intrauterine pregnancy - although in an ectopic pregnancy, this appearance may be mimicked by a pseudosac (a collection of fluid within the endometrial cavity created by bleeding from the decidualized endometrium). Depending on the fetal age, the presence of a yolk sac, fetal pole or fetal cardiac activity may be used to confirm the presence of a true gestational sac. Note that presence of an intrauterine pregnancy does not completely exclude an ectopic pregnancy, as between 1 in 30,000 to 1 in 4,000 pregnancies may be heterotropic (have multiple gestational sacs). This is more common in patients who have undergone assisted reproductive therapy, who should be evaluated especially carefully. A subpopulation of patients may have indeterminate ultrasound findings. In such cases estimation of serum beta-hCG levels should be the next step. In general, when serum beta-hCG levels exceed 1000 to 5000 mIU/ml (the so called "discriminatory threshold"), an intrauterine pregnancy should be visualizable in a pelvic ultrasound scan. Thus, if these patients with equivocal ultrasound findings have a beta-hCG level in excess of the discriminatory threshold, they are very likely to have an ectopic pregnancy. If the beta-hCG level is lower than the discriminatory threshold, the diagnoses are either a non-viable intra-uterine pregnancy, a viable intra-uterine pregnancy with incorrect dates, or an ectopic pregnancy. In such a scenario, serial estimation of beta-hCG levels should be performed, and an ultrasound scan repeated if or when they bypass the discriminatory threshold. If an intrauterine pregnancy is detected, the diagnosis is either a threatened miscarriage or an early pregnancy failure, which should be further classified into either a missed miscarriage, inevitable miscarriage or incomplete miscarriage. If the cervical os is closed and the fetus is viable, the diagnosis is a threatened miscarriage; whereas if the fetus is non-viable, a missed miscarriage is present. If the cervical os is open, but no products of conception have been expelled, the diagnosis is an inevitable miscarriage; while if products of conception have been expelled, an incomplete miscarriage is present. Note that if the cervical os is open and all products of conception have been expelled, the diagnosis is a complete miscarriage - however this condition rarely presents a diagnostic dilemma. If an ectopic pregnancy is diagnosed, surgery or medical therapy (i.e. methotrexate) should be considered, depending on the condition of the patient. If a threatened miscarriage is present, the patient is usually managed expectantly, as a percentage of these pregnancies continue successfully. If a missed, inevitable or incomplete miscarriage is diagnosed, the further management may be expectant, medical or surgical. Surgical modalities of treatment include dilatation and curettage or manual vacuum aspiration. While prompt surgical evacuation of the uterus has been traditionally recommended because of concerns of infection and or coagulation disorders (from retained products of conception), recent evidence shows that medical or expectant management may be considered in a significant proportion of patients. Expectant management has a high success rate of 82% to 96% in patients with incomplete or inevitable miscarriage (where the time to completion is around 9 days), but is only successful in 16% to 76% of patients with missed miscarriage. Although the policy varies by unit, up to 2 weeks of expectant management may be considered. Medical therapy has not been shown to be significantly more effective than expectant management in patients with incomplete or inevitable miscarriage. However, medical therapy for missed miscarriage has a high success rate of over 80%. All patients who are Rhesus negative should be administered anti-D immunoglobulin to prevent sensitization. In addition, if a history of multiple miscarriages is present, further evaluation to detect an underlying cause (such as anti-phospholipid syndrome or uterine abnormalities) should be considered.