Causes of infertility

Physical causes in women

Disturbance of egg maturation

The production and secretion of hormones are affected by various factors. For example, stress, certain types of medication, weight or metabolic disorders can have a negative impact on hormone balance. Hormone imbalance has a major impact on the natural course of the menstrual cycle. For example, the maturation of eggs and subsequent ovulation may be disturbed or not take place at all.   

Reduced function of the fallopian tubes  

After ovulation, the egg must pass through the fallopian tube, where it is fertilised by sperm. In some women, the fallopian tubes are blocked or damaged. This can be caused by infection (e.g. chlamydia), scar tissue (after surgery or perforated appendix) or endometriosis. Damaged fallopian tubes increase the risk of ectopic pregnancy. If the fallopian tubes are blocked, fertility treatment with IVF is necessary.  

Muscle nodules in the uterus

Muscle nodules in the uterus are also called fibroids. They are benign, but they can interfere with a fertilised egg attaching to the lining, depending on their location.  If there is any doubt that a muscle lump could affect the chance of pregnancy, a 3D scan or hysteroscopy can be done to investigate further. In some cases, it may be necessary to remove the fibroid(s) before fertility treatment.   

Male reproductive ability  

During sexual intercourse, the motile sperm is pushed out through the vas deferens and urethra by muscle contractions during ejaculation. The motile sperm penetrate via the vagina into the cervix and uterus and into the fallopian tubes. If there is a mature egg in the fallopian tube, the sperm try to break down the egg's cell wall and attach themselves inside the cell, thus fertilising the egg. On the way into the fallopian tube, many sperm cells succumb, which is why a single ejaculation contains 200-300 million sperm cells (2-5 ml). If the amount of sperm is significantly below this average, or if the sperm in the ejaculate are not sufficiently motile, the man's reproductive ability may be adversely affected.   

What factors determine sperm quality?  

The causes of involuntary infertility can is a complex interplay of factors which can originate with the woman and/or the man. The most common reason for a fertility disorder in men is insufficient production of normally formed, motile sperm. For "normal" sperm quality, the following factors apply according to WHO guidelines:   

• Amount of ejaculate: 1.5 ml or more 

• Total number of sperm cells in the ejaculate: At least 40 million sperm cells 

• Sperm concentration: At least 20 million sperm/ml 

• Morphology of sperm: At least 15 % normally shaped 

• Sperm motility: At least 50 % with forward motility or 25 % with progressive motility within 60 min. after ejaculation.