Sometimes the fallopian tubes become blocked either by the surrounding organs that can ‘strangle’ the narrow tube, such as adhesions following a previous surgery to the abdomen or infections such as appendicitis or peritonitis, or internally from infection. In the latter case, the most frequent cause is infection from chlamydia, which acts upon and distorts the delicate surface of the tubes’ pipes.
Other common causes of blocking are endometriosis or previous ectopic pregnancies with or without surgical removal of the fallopian tube while congenital abnormalities are rare.
Of course, when a fallopian tube is blocked, the egg cannot encounter the sperm, and so fertilisation does not occur. When only one fallopian tube is blocked, the chances of fertilisation are reduced but not by exactly 50%, since it has been found that sometimes the egg released by one ovary may travel in the opposite fallopian tube–.
If both fallopian tubes are blocked or have been surgically removed, clearly there is no possibility of natural conception. This is precisely why IVF was invented, to offer the possibility of the egg encountering the sperm without the mediation of the fallopian tubes.
Hydrosalpinx is a special case of blocked fallopian tube since inflammatory fluid is produced and collects inside it, which may destroy the embryo that will be transferred in the case of IVF. So, even though hydrosalpinx is not a threat to a woman’s overall health, for women who are going to undergo IVF it is recommended to have the blocked fallopian tubes removed laparoscopically.
The percentage of women with blocked fallopian tubes may exceed 30%, even in women who have already achieved pregnancy or birth and are attempting a subsequent pregnancy. The patency of fallopian tubes is diagnosed either conventionally with salpingography, or with other methods such as laparoscopy, hysteroscopy, and in some cases hysterosalpingo-contrast-sonography (HyCoSy), a special form of ultrasound.