Risk Factors & Pathogenesis
Ectopic pregnancy occurs in the fallopian tube in over 95% of cases. Other locations for ectopic pregnancies are rare: abdominal, ovarian or cervical. The most common location in the fallopian tube for ectopic pregnancies to occur is the ampulla (70.0%); other locations, such as the isthmus (12.0%), the fimbria (11.1%) and the cornua (2.4%), are less common (Figure 1). The ampullar portion of the fallopian tube is more distendable than other areas. Ectopic pregnancies in this location may result in tubal abortion and not be recognized clinically. The isthmus of the fallopian tube is not able to expand to accommodate a growing ectopic pregnancy and is more prone to rupture.
Locations of fallopian tube ectopic pregnancy. Adapted from reference 54.
Patients with certain risk factors are known to be at higher risk of developing ectopic pregnancy. Patients who have had a previous ectopic pregnancy, who have had previous tubal surgery, who have documented tubal pathology, who have known in utero diethystilbestrol exposure or who are undergoing assisted reproductive technologies are at relatively high risk of developing an ectopic pregnancy if they were to become pregnant. Patients with infertility, previous genital infections including gonorrhea and chlamydia, or who have greater than one lifetime sexual partner are at moderately increased risk. Overall, patients who have an intrauterine device (IUD) or who have had a tubal ligation are at decreased risk of ectopic pregnancy compared with nonpregnant controls. However, if women become pregnant with an IUD in place or after a tubal ligation, they are at increased risk for having an ectopic pregnancy compared with women who conceive without an IUD or tubal ligation ( Table 1 ).
Ectopic pregnancies may occur owing to impaired migration of the fertilized ovum in the fallopian tube, resulting from inflammation, hormonal or other factors. If the passage of the fertilized ovum is slowed and hatching occurs prior to the ovum reaching the endometrial cavity, the embryo may implant in the fallopian tube. Intrinsic factors to the embryo do not seem to contribute to ectopic pregnancy. In a series analyzing the chromosomes of abnormally implanted embryos, no karyotype abnormalities were noted.[6,7] Research is now focusing on the molecular signaling at the time of blastocyst implantation and identifying abnormalities in this event that may further explain the etiology of ectopic gestations.
Women's Health. 2008;4(1):79-87. © 2008 Future Medicine Ltd.
Cite this: Ectopic Pregnancy: Diagnosis and Management - Medscape - Jan 01, 2008.