Ectopic pregnancy is the implantation of fertilized ovum outside the uterine endometrial cavity.
Ectopic pregnancy is life-threatening gynecological emergency and a significant cause of maternal morbidity and mortality.
So,
early and accurate diagnosis of ectopic pregnancy is very critical (1).
Although the incidence of ectopic pregnancy is estimated between 1% and 2%,
the majority of these pregnancies are located in the fallopian tube accounting for nearly 95% cases.
However,
about 5% pregnancies implanted in cervix,
ovary,
previous cesarean scar,
interstitial portion of the fallopian tube and abdomen as well as angular ectopic pregnancy and heterotopic pregnancy (2).
Transvaginal ultrasound is the first and the modality image of choice for diagnosis of ectopic pregnancy.
However,
in some ectopic pregnancies,
the ultrasound may be inconclusive; MRI in these situations is useful problem-solving adjunct to ultrasound because MRI provides images with high soft-tissue contrast,
which help to localize the ectopic gestational sac when it is not clearly identified with ultrasound (3).
1. Tubal ectopic pregnancy
The most common site of ectopic pregnancy is fallopian tube.
In the fallopian tube,
the ampulla (70%–80%) is the most common site,
followed by an isthmus (12%) and fimbria (5%).
Most cases of tubal ectopic pregnancy that are detected early can be treated successfully either with minimally invasive surgery or with medical management using methotrexate.
However,
tubal ectopic pregnancy in an unstable patient is a medical emergency that requires prompt surgical intervention (4).
2. Interstitial ectopic pregnancy
Interstitial pregnancies account for 2%–4% of all ectopic pregnancies.
It occurs when implantation takes place in the interstitial or intramyometrial segment of the fallopian tube.
The diagnosis of an interstitial pregnancy is quite challenging because it is difficult to distinguish it from an eccentric intrauterine pregnancy (5).
3. Cervical ectopic pregnancy
Cervical Pregnancy is a rare sub type of ectopic pregnancy accounting for 0.15 – 1 % of all ectopic pregnancies.
Implantation occurs in the lining of the endocervical canal below the level of the internal cervical Os.
A cervical ectopic pregnancy may be misdiagnosed as a miscarriage in progress or as a nabothian cyst (6).
4. Ovarian ectopic pregnancy
Ovarian Pregnancy is a rare sub type of ectopic pregnancy accounting for 1-3 % of all ectopic pregnancies.
It results when a fertilized ovum is retained in the ovary.
An ovarian ectopic pregnancy may be misdiagnosed as corpus luteum cyst or ruptured hemorrhagic cyst if yolk sac or fetal pole are absent (7).
5. Cesarean scar ectopic pregnancy
Cesarean scar pregnancy is rare and represents less than 1% of ectopic pregnancies.
The incidence of cesarean scar pregnancy has steadily increased over the years,
secondary to the rise in cesarean delivery rates.
Cesarean scar ectopic pregnancy occurs when a blastocyst implant in the anterior lower uterine segment at the site of a cesarean scar.
Early diagnosis of cesarean scar pregnancy is essential because of the inherent risk for uterine rupture and uncontrollable hemorrhage.
Most common differential diagnosis of Cesarean scar ectopic pregnancy is cervical ectopic pregnancy (8).
6. Abdominal ectopic pregnancy
Abdominal ectopic pregnancies are extremely rare,
accounting about 0.9%–1.4%,
which can go undetected until very late gestational age.
It occurs when the gestational sac is implanted in the abdominal cavity outside the uterus,
fallopian tube,
and ovaries.
Implantation can occur on omentum,
vital organs,
or great vessels (9).
7. Heterotopic pregnancy
Heterotopic pregnancy is a rare situation accounting about 0.6‑2.5: 10,000 pregnancies.
It occurs when there is intra-uterine and extra-uterine (i.e.
ectopic) pregnancy occurring simultaneously.
Differential diagnoses: Normal intrauterine pregnancy,
a normal intrauterine pregnancy and a ruptured ovarian cyst,
corpus luteum,
or an appendicitis (10).
8. Rudimentary horn pregnancy
Pregnancy in a rudimentary horn of the uterus is a rare condition with reported incidence of 1 in 100,000 to 140,000 pregnancies. The majority of cases are diagnosed late,
after the rupture has occurred. Common misdiagnoses with ultrasonography include an ectopic,
cornual,
intrauterine or abdominal pregnancy (10).