Ectopic pregnancy pathophysiology
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Moises Romo M.D.
Overview
Normal physiology
- The normal site of implatation for a pregnancy is always the uterus, most of them occuring the upper third and posterior walls of the uterine body (corpus uteri); lower implantations may cause a placenta previa.
- Normaly, after fecundation, the blastocyst begins to implant in the endometrium at day 7 after fecundation (8-10 days after ovulation in most successful cases) and is completed by day 9.[1][2] By this time the level of HCG is usually higher than 5000mIU/mL.
- The discriminatory level of hCG for a pregnancy is around 1000 mIU/mL.[3][4]
- In most normal pregnancies at an hCG level below 1,200 mIU/ml, the hCG usually doubles every 48-72 hours. At levels below 6,000 mIU/ml, the hCG levels normally increase by at least 60% every 2-3 days.
Pathophysiology
Cilial Damage and Tube Occlusion
Hair-like cilia located on the internal surface of the Fallopian tubes carry the fertilized egg to the uterus. Damage to the cilia or blockage of the Fallopian tubes is likely to lead to an ectopic pregnancy. Women with pelvic inflammatory disease (PID) have a high occurrence of ectopic pregnancy. This results from the build-up of scar tissue in the Fallopian tubes, causing damage to cilia. If however both tubes were occluded by PID, pregnancy would not occur and this would be protective against ectopic pregnancy. Tubal surgery for damaged tubes might remove this protection and increase the risk of ectopic pregnancy. Tubal ligation can predispose to ectopic pregnancy. Seventy percent of pregnancies after tubal cautery are ectopic, while 70% of pregnancies after tubal clips are intrauterine. Reversal of tubal sterilization (Tubal reversal) carries a risk for ectopic pregnancy. This is higher if more destructive methods of tubal ligation (tubal cautery, partial removal of the tubes) have been used than less destructive methods (tubal clipping). A history of ectopic pregnancy increases the risk of future occurrences to about 10%. This risk is not reduced by removing the affected tube, even if the other tube appears normal. The best method for diagnosing this is to do an early ultrasound.
Association with Infertility
Infertility treatments are highly variable and specific to individual patients. In vitro fertilization is used for patients with damaged tubes, which are an inherent risk factor for ectopic pregnancy. Ectopic pregnancies have been seen with in vitro fertilization, but this is an uncommon complication and quickly diagnosed by the early ultrasounds that these intensively surveyed patients undergo.
Hysterectomy
Ectopic pregnancy occasionally occurs in women who have had a hysterectomy. Rather than implanting in the absent uterus, the fetus implants in the abdomen, and must be delivered via caesarean section.[5]
Other
Patients are at higher risk for ectopic pregnancy with advancing age. Also, it has been noted that smoking is associated with ectopic risk. Vaginal douching is thought by some to increase ectopic pregnancies; this is speculative. Women exposed to diethylstilbestrol (DES) in utero (aka "DES Daughters") also have an elevated risk of ectopic pregnancy, up to 3 times the risk of unexposed women.
Associated conditions
Gross pathology
Microscopic pathology
| Organs | Light microscope | Electron microscope | Images |
|---|---|---|---|
| Organ 1 | Characteristic 1a | Characterstic 1b | Image 1 |
| Organ 2 | Characteristic 2a | Characterstic 2b | Image 2 |
| Organ 3 | Characterstic 3a | Characterstic 3b | Image 3 |
References
- ↑ "Implantation - Embryology".
- ↑ Goldstein SR (May 2008). "Early pregnancy: normal and abnormal". Semin Reprod Med. 26 (3): 277–83. doi:10.1055/s-2008-1076146. PMID 18504702.
- ↑ Goldstein SR, Snyder JR, Watson C, Danon M (August 1988). "Very early pregnancy detection with endovaginal ultrasound". Obstet Gynecol. 72 (2): 200–4. PMID 3292977.
- ↑ Bree RL, Edwards M, Böhm-Vélez M, Beyler S, Roberts J, Mendelson EB (July 1989). "Transvaginal sonography in the evaluation of normal early pregnancy: correlation with HCG level". AJR Am J Roentgenol. 153 (1): 75–9. doi:10.2214/ajr.153.1.75. PMID 2660539.
- ↑ SA Carson, JE Buster, Ectopic Pregnancy. New Engl J Med 329:1174-1181