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
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). hCH levels in an ectopic pregnancy are usually lower than in uterine pregnancies. No visible intruterine transvaginal utrasonography with a serum hCG higher than 2000 mIU/ml is indicateive of an ectopic pregnancy. The most common site of ectopic pregnancies is in the Fallopian tubes (80% ampullar). An ectopic pregnancy may be seen in gross pathology as a distension of the Fallopian tube. Histopathological findings of ectopic pregnancies are intraluminal chorionic villi and extravillous trophoblast (may be degenerated) with variable fetal parts.
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.
- Hair-like cilia located on the internal surface of the Fallopian tubes carry the fertilized egg to the uterus.
- 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
- The most common site of ectopic pregnancies is in the Fallopian tubes (80% ampullar).
- hCH levels in an ectopic pregnancy are usually lower than in uterine pregnancies.
- No visible intruterine transvaginal utrasonography with a serum hCG higher than 2000 mIU/ml is indicateive of an ectopic pregnancy.
Cilial Damage and Tube Occlusion
- Damage to the cilia or blockage of the Fallopian tubes is likely to lead to an ectopic pregnancy.
- A common cause of Fallopian tubes occlusion and damage to cilia is by scaring of tissues after pelvic inflammatory disease (PID).
- Tubal ligation can predispose to ectopic pregnancy, variably increasing the risk depending on the method used. Seventy percent of pregnancies after tubal cautery are ectopic, while seventy percent of pregnancies after tubal clips are intrauterine. Reversal of tubal sterilization (Tubal reversal) still carries an additional risk for ectopic pregnancy when comparing with normal women.[5]
- Normal pregnancy may still be possible if only one Fallopian tube is occluded.
- A history of ectopic pregnancy increases the risk of future occurrences in about 10%.[6]
Association with Infertility
- Infertility management is 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
- In rare occasions, ectopic pregnancies may occur in women who underwent an hysterectomy. Blastocysts, rather than implanting in the absent uterus, the fetus implants in the abdomen.
- In most of these cases, a laparotomy is indicated.[7]
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
- The most important conditions/diseases associated with ectopic pregnancy include:
- Pelvic inflammatory disease (PID)
- Previous ectopic pregnancy
- Previous surgery on your fallopian tubes
- Fertility treatment, such as in-vitro fertilization (IVF)
- Becoming pregnant while using an intrauterine device (IUD) or intrauterine system (IUS) for contraception
- Smoking
- Increasing age after 40 years old
Gross pathology
Ectopic pregnancy may reveal in gross pathology a distension of the Fallopian tube with thin or ruptured wall, dusky red serosa and hematosalpinx, possibly with fetal parts identified.
Microscopic pathology
Histopathological findings in an ectopic pregnancy may be the following:
- Intraluminal chorionic villi and extravillous trophoblast (may be degenerated); variable fetal parts.
- Decidual change in lamina propria in 1/3; mesothelial reactive proliferation with papillary formation and psammoma bodies.
- Uterus: gestational hyperplasia with Arias-Stella reaction, no enlarged, hyalinized spiral arteries, no fibrinoid matrix.
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.
- ↑ Shah JP, Parulekar SV, Hinduja IN (January 1991). "Ectopic pregnancy after tubal sterilization". J Postgrad Med. 37 (1): 17–20. PMID 1941685.
- ↑ "Ectopic pregnancy: Future fertility - Mayo Clinic Health System".
- ↑ SA Carson, JE Buster, Ectopic Pregnancy. New Engl J Med 329:1174-1181