What is the difference between a tubal pregnancy and an ectopic pregnancy?
In ectopic pregnancy, implantation occurs in a site other than the endometrial lining of the uterine cavity, i.e., in the fallopian tube, horn of the uterus, cervix, ovary, or abdominal or pelvic cavity. Ectopic pregnancies cannot be carried to term and eventually rupture or involute.
Early symptomatology includes pelvic pain, metrorrhagia, and tenderness to the vaginal touch, especially when the cervix is displaced.
Syncope or hemorrhagic shock may occur upon rupture. Diagnosis is based on beta-hCG measurement and pelvic ultrasound. Treatment consists of laparoscopic or open surgical resection or IM methotrexate injection.
The incidence of ectopic pregnancy is approximately 2/100 diagnosed pregnancies.
Etiology of ectopic pregnancy
Factors that particularly increase the risk of ectopic pregnancy include
Tubal lesions
A history of ectopic pregnancy (risk of recurrence 10-25%)
History of pelvic inflammatory disease (especially Chlamydia trachomatis)
Previous abdominal surgery especially on the fallopian tubes, including tubal ligation
Other specific risk factors for ectopic pregnancy include
Intrauterine device (IUD) contraception
Infertility due to tubal damage
Smoking
History of induced abortion
Pregnancy is less likely to occur when an intrauterine device (IUD) is in place; however, about 5% of these pregnancies are ectopic.
Pathophysiology of ectopic pregnancy
The most common location of ectopic pregnancies is the fallopian tube, followed by the uterine horn. Cervical pregnancies, in a caesarean scar, the ovary, the abdomen or the interstitium of the fallopian tube are rare.
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Heterotopic pregnancies (both ectopic and intrauterine) occur in only 1/10,000 to 30,000 pregnancies, but may be more common among women who have used ovulation induction or assisted reproductive technologies such as in vitro fertilization and gamete intrafallopian tube transfer (GIFT); in such cases, the reported rate of ectopic pregnancies is ≤ 1%.
The structure containing the fetus usually ruptures after 6 to 16 weeks. Rupture results in hemorrhage that may be progressive or rapid enough to cause hemorrhagic shock. Intraperitoneal blood irritates the peritoneum. The later the rupture, the more rapid the bleeding and the higher the mortality.
Symptomatology of ectopic pregnancy
Symptoms of ectopic pregnancy vary and are often absent until rupture occurs. Most patients present with pelvic pain (sometimes in the form of cramping) and/or vaginal bleeding. There may or may not be a delay or absence of menstrual bleeding, and the patient may not know that she is pregnant.
Rupture may be heralded by sudden severe pain, followed by syncope or symptoms of hemorrhagic shock or peritonitis. Rapid hemorrhage is more likely in ruptured ectopic pregnancies.
Pain on mobilization of the cervix, unilateral or bilateral adnexal tenderness on vaginal touch, or an adnexal mass may be present. The uterus may be slightly enlarged (but less than expected from delayed menstruation).
Diagnosis of ectopic pregnancy
Quantitative serum human chorionic gonadotropin beta subunit (beta-hCG)
Pelvic ultrasound
Sometimes laparoscopy
An ectopic pregnancy is suspected in any woman of childbearing age with pelvic pain, metrorrhagia, or unexplained syncope or hemorrhagic shock, regardless of contraceptive use, sexual intercourse, or delayed menses. The results of physical examinations (including pelvic touch) are neither sensitive nor specific.
A ruptured ectopic pregnancy is a surgical emergency because it causes maternal hemorrhage with a risk of death; prompt diagnosis is essential.
The first step is a urine pregnancy test, which is nearly 99% sensitive in diagnosing pregnancies (ectopic and others). When the urine beta-hCG test is negative and the clinical signs are not strongly suggestive of ectopic pregnancy, further testing is unnecessary unless the symptoms recur or worsen.
If the urine beta-hCG is positive or the clinical signs are strongly suggestive of ectopic pregnancy, a quantitative serum beta-hCG measurement and pelvic ultrasound are not indicated.
When the quantitative serum beta-hCG is < 5 mIU/mL, ectopic pregnancy is excluded. When ultrasound detects an intrauterine gestational sac, an ectopic pregnancy is highly unlikely except in the woman who has used assisted reproductive techniques (which increases the risk of heterotopic pregnancy); however, a cornual or intra-abdominal pregnancy may initially present as an intrauterine pregnancy.
Ultrasound images suggestive of an ectopic pregnancy (seen in 16 to 32%) of cases include complex masses (mixed solid and cystic masses), particularly in the adnexa, and fluid effusion from the cul-de-sac of Douglas.
If the serum beta-hCG is above a certain level (called the discriminatory zone), the ultrasound should detect a gestational sac in case of intrauterine pregnancy. This level is usually about 2000 mIU/mL. If the beta-hCG level is above the discriminatory zone and no intrauterine gestational sac is detected, an ectopic pregnancy is likely. The use of the transvaginal route or color Doppler can improve detection rates.
If the beta-hCG level is below the discriminatory zone and the ultrasound is negative, it may be an early intrauterine pregnancy or an ectopic pregnancy. If the initial clinical workup suggests an ectopic pregnancy (e.g., significant peritoneal irritation or hemorrhage), diagnostic laparoscopy may be necessary for confirmation.
When an ectopic pregnancy appears unlikely and the patient is stable, plasma beta-hCG levels can be monitored on an outpatient basis (typically every 2 days). Normally, the level doubles every 1.4 to 2.1 days until day 41; in an ectopic pregnancy (as in non-progressive pregnancies), levels may be lower than expected and do not double as rapidly.
If the beta-hCG level does not rise as expected or falls, the diagnosis of spontaneous miscarriage or ectopic pregnancy should be considered.
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