There are two tubes on either side which connect the ovaries to the uterus. These are the fallopian tubes, and in the majority of the cases, this is where the fusion between the egg and the sperm happens. If there is any problem in either of the fallopian tubes, then the egg cannot travel down into the uterus and there cannot be fusion. Tubal infection or salpingitis and blocked fallopian tubes are some of the most common causes of infertility. In some cases, the sperm may travel up the fallopian tube halfway till the area of blockage and fuse with the egg. This is known as ectopic pregnancy, which is out of place.
Tubal infection is often a result of sexually transmitted diseases including trichomonas, gonococci, and chlamydia. Other general bacteria like strep and staph also produce salpingitis. In most cases, tubal ligation per se is not an issue. However, it can cause problems like blocked tubes or hydrosalpinx. In these cases, the complications arise. In some women, treating these could be the cure for their infertility itself. Blocked fallopian tubes can stop the eggs from traveling down the ovaries and fuse with the sperm. If the block is removed, then infertility is solved. Similarly, if the tubes are filled with pus as a result of the infection, then it does not produce a conducive environment for fertilization.
With IVF being used as a treatment for infertility, the tubes need to be cleared for infection or blockages. These might continue to pose problems and reduce the overall success rate of IVF. These are easy to diagnose so that the infection can be completely cleared and pus drained if required. Surgical debridement can also be done if required so that the tubes are cleared. In some cases, a part of the tube may be removed so that the issue is addressed completely. A course of antibiotics is often required to completely clear the infection. After that, once ovulation is stimulated, then the eggs can travel down so that they can be retrieved and frozen for further use.
Undetected blocked fallopian tubes of silent infection (chronic salpingitis, which does not present with any symptoms) can be one of the causes of failure to conceive with IVF. This can be quite demotivating for both the couple and the medical team. With IVF, there is no clear role for the fallopian tubes, as the eggs can be retrieved from the ovaries and placed directly in the uterus. So, in severe cases of infection, the tube(s) may be even completely removed to improve chances of fertility.