Causes of Infertility — Core Principles

Core Principles

Infertility is defined as the inability to achieve pregnancy after 12 months of regular, unprotected intercourse (or 6 months if the female is over 35). It can be primary (never conceived) or secondary (previously conceived but now unable). Causes are diverse and can originate from the male partner, female partner, or a combination of both, with some cases remaining unexplained.

Male infertility often stems from issues with sperm production (e.g., low count, poor motility, abnormal shape due to conditions like varicocele, hormonal imbalances, or genetic defects), sperm transport blockages, or ejaculatory dysfunction.

Female infertility commonly arises from ovulatory disorders (like PCOS, premature ovarian failure), fallopian tube damage or blockage (often from PID or endometriosis), uterine abnormalities (fibroids, polyps, congenital defects), or cervical factors.

Age is a significant factor for female fertility, with a decline after 35. Lifestyle choices such as smoking, excessive alcohol, drug use, and extreme weight also contribute to infertility in both sexes.

Understanding these broad categories is crucial for diagnosis and treatment.

Important Differences

vs Secondary Infertility

Aspect	This Topic	Secondary Infertility
Definition	Inability to conceive after 12 months (or 6 months if female >35) of unprotected intercourse, having never conceived before.	Inability to conceive after 12 months (or 6 months if female >35) of unprotected intercourse, after having conceived at least once previously.
Prior Pregnancy History	No prior successful pregnancy (live birth, miscarriage, ectopic).	At least one prior successful pregnancy (live birth, miscarriage, ectopic).
Common Causes (Examples)	Congenital abnormalities, severe genetic conditions, long-standing hormonal imbalances (e.g., untreated PCOS from adolescence), severe endometriosis.	Acquired conditions like pelvic inflammatory disease (PID) after a previous pregnancy, Asherman's syndrome (intrauterine adhesions from D&C), age-related decline in ovarian reserve, new onset male factor issues, lifestyle changes.
Diagnostic Approach	Often involves a comprehensive initial workup for both partners, looking for fundamental reproductive issues.	May focus more on acquired conditions or changes since the last pregnancy, though a full workup is still necessary.

Primary infertility refers to couples who have never achieved a pregnancy, whereas secondary infertility applies to couples who have conceived at least once before but are now unable to do so again. This distinction is important because while some causes can be common to both, secondary infertility often points towards acquired conditions or changes that have occurred since the last successful pregnancy, such as new infections, surgical complications, or age-related decline. Understanding the history helps guide diagnostic investigations and treatment strategies, as the focus might shift from congenital issues to acquired ones.