**3. Risk factors**

Multiple factors contribute to the relative risk of ectopic pregnancy although some patients may not have any risk factor yet developed ectopic pregnancy. In theory, any thing that hampers or delays the migration of the embryo to the endometrial cavity could predispose women to ectopic pregnancy. Age, marital status, and parity have been found not to be significant risk factors for ectopic pregnancy (Anorlu et al, 2005). The reported aetiological factors for ectopic pregnancy include pelvic inflammatory disease, post abortal sepsis, postpartum sepsis, previous ectopic pregnancy, reversal of previous tubal sterilization, tubal spasm, long defects of the fallopian tubes and psychological and emotional factors (Doyle et al, 1991).

**Pelvic inflammatory disease**: Pelvic inflammatory disease from inappropriate obstetric care or from unsafe abortion is a risk factor for ectopic pregnancy (Onwuhafua et al, 2001). These infection causes distortion in the genital tract and the fallopian tube in particular. Unsafe abortion leads to post abortal sepsis. Induced abortion and sexually transmitted disease increases the risk four fold and nine-fold respectively (Anorlu et al, 2005). Also, multiple sexual partners predispose the patient to acquiring sexually transmitted disease. Pelvic inflammatory disease is a major risk factor for developing ectopic pregnancy in Nigeria (Olarewaju, 1994, Egwuatu & Ozumba, 1987). Induced abortion as a significant risk factor for ectopic pregnancy was not observed in studies from countries where abortion is legalised (Atrash et al, 1997). This is because qualified medical personnel carry it out under aseptically clean environment with sterile instruments. Biologically the adolescent is particularly at risk of sexually transmitted disease because the columnar epithelium, which is susceptible to *Chlamydia* and *gonococci* organism extends from the endocervical canal to the ectocervix making it fully exposed to pathogens. Adolescents also lack immunity to certain pathogens. Early sexual debut may also lead to adolescent pregnancy which is often unwanted and which usually end up with induced abortion in unsafe places and in the hands of quacks. Late age of sexual debut on the other hand, significantly reduces the risk of ectopic pregnancy (Anorlu et al, 2005). In a study in France by Coste J et al, found that *Chlamydia trachomatis* seropositively appeared to be an important risk factor in the development of ectopic pregnancy. Pelvic inflammatory disease is a risk factor for ectopic pregnancy especially salpingitis. A case control study conducted showed that the risk of ectopic pregnancy was showed that the risk of ectopic pregnancy was increased four fold with induction of ovulation (Fernandez et al, 1991).

**Assisted conception**: Ectopic pregnancy is one of the recognised complications of in-vitro fertilization and embryo transfer (Okohue et al, 2010). Ectopic pregnancy can present following an in vitro fertilization procedures. A high index of suspicion is necessary even in cases with previous bilateral salpingectomies or easy embryo transfer.

**Intrauterine contraceptive device (IUCD):** The use of intrauterine contraceptive device increases the risk of developing an ectopic pregnancy almost four fold (Anorlu et al, 2005).

**Previous history of ectopic pregnancy**: Previous history of an ectopic pregnancy increases the risk for another ectopic pregnancy. The risk of recurrent ectopic pregnancy is 12-18 % (Jurkovic, 2007). Every woman with a previous ectopic pregnancy would be at a high risk of recurrence of another ectopic pregnancy. This should be excluded when a patient with a previous ectopic pregnancy presents in early pregnancy.

**Tubal surgery**: Scarring following tubal surgery causes anatomical abnormalities of the fallopian tube, which presents abnormal embryo transport increase the risk of ectopic pregnancy (Doyle et al, 1991).

**Previous caesarean delivery**: There has not been any evidence of increased risk of ectopic pregnancy related to previous caesarean section (Kendrick et al, 1996). However, there are reports of ectopic pregnancies implanting on previous caesarean section scars. Endometrial and myometrial disruptions or scaring can predispose to abdominal pregnancy implantation (Fylstra, 2002).
