Ovule production of a woman's ovary must be strong and one for a time. This process is called ovulation. Other important factor is your husband must have a good healthy sperm ejection. Third factor is you have to do the intercourse on your fertile period. Fourth fact is fallopian tube and the womb must be healthy. Ovule and sperm contacts in fallopian tube. Therefore fallopian tube must be clear. The zygote grow in womb and womb must be prepare the facilities for a successful growth.
There are some difficulties to avoid fertilization. 25 percent of those due to the difficulties of ovule emitting. This is stimulated by hormones. Specially a reduction of hormone generation of hypothalamus and pituitary glands affect to difficulties of ovulation. Or it can be happened due to a physical defect of ovary.
Polycystic Ovary Syndrome (PCOS)
There can be form complicated changes on Hypothalamus, Pituitary and Ovary due to this syndrome. There can be difficulties on hormone emission of those organs. Here a woman can also form a diabetes status due to insulin resistance. Increases hair formation on face and all over the body.
There are two hormones help to continue menstrual cycle correctly. These hormones are Follicle Stimulation Hormone (FSH) and Luteinizing hormone (LH) and both of these generate in Pituitary gland. High stress, high weight or large weight loss can affect to reduce the action of hypothalamus. Irregular menstrual cycle or fully stopped menstrual cycle is the symptoms.
Premature Ovarian Insufficiency
A wrong signal due to self immunization fault is caused for this. Here ovules damage before mature. This can be happen because of genetic problem. And this can also happen due to Chemotherapy which is doing on cancer treatments.
High prolactin secretion
Prolactin reduces the emission of estrogen. Basically a fault of pituitary gland is caused for this. And this also can happen due to a drug or other external issue.
Failures of fallopian tube
This also cause to difficulties of pregnancy. When fallopian tube blocks sperms could not be able to come through it. If it comes to the ovule and successful fertilization happens, zygote could not be able to come to the womb.
Causes for fallopian tube blocks
Pelvic Inflammatory Disease
Chlamydia and Gonorrhea like sexual transmission diseases responsible for this. And also incorrect placements of birth control systems, damage due to illegal abortions and intercourse in menstruation may cause for this. Because germs can enter easily on such actions. Surgeries, specially surgeries for ectopic pregnancy may also cause for this disease. Pelvic tuberculosis also reduce the softness of fallopian tubes.
Endometriosis
Because of some reason menstrual blood goes up and enter to the cavity abdominal and forms clots. This causes to endometriosis. This will results a unusual large pain during the menses. And also you may feel a pain on sexual intercourse. To identify this disease we normally use a laparoscopy test.