Biology·Core Principles

Infertility — Core Principles

NEET UG
Version 1Updated 22 Mar 2026

Core Principles

Infertility is defined as the inability to conceive after 12 months of unprotected intercourse (or 6 months for women over 35). It can stem from male factors (e.g., low sperm count, poor motility), female factors (e.

g., ovulatory disorders like PCOS, blocked fallopian tubes, endometriosis, uterine issues), or a combination of both, sometimes remaining unexplained. Diagnosis involves assessing both partners through semen analysis, hormone tests, and imaging.

To overcome infertility, Assisted Reproductive Technologies (ARTs) are employed. Key ARTs include In Vitro Fertilization (IVF), where fertilization occurs outside the body and embryos are transferred to the uterus; Zygote Intrafallopian Transfer (ZIFT), where in vitro fertilized zygotes are placed in the fallopian tube; Gamete Intrafallopian Transfer (GIFT), where eggs and sperm are placed directly into the fallopian tube for in vivo fertilization; Intracytoplasmic Sperm Injection (ICSI), where a single sperm is injected into an egg; and Artificial Insemination (AI), involving direct introduction of sperm into the female reproductive tract.

These technologies offer pathways to parenthood for many infertile couples.

Important Differences

vs IVF, ZIFT, and GIFT

AspectThis TopicIVF, ZIFT, and GIFT
Full FormIn Vitro Fertilization (IVF)Zygote Intrafallopian Transfer (ZIFT)
Fertilization LocationOutside the body (in vitro)Outside the body (in vitro)
Transferred StageEmbryo (2-8 cell stage or blastocyst)Zygote (fertilized egg)
Transfer LocationUterusFallopian tube
Fallopian Tube RequirementNot required (can bypass blocked tubes)Required (at least one healthy tube)
ProcedureOvarian stimulation, egg retrieval, in vitro fertilization, embryo culture, uterine transfer.Ovarian stimulation, egg retrieval, in vitro fertilization, zygote transfer to fallopian tube.
IVF, ZIFT, and GIFT are all Assisted Reproductive Technologies (ARTs) aimed at helping infertile couples, but they differ fundamentally in where fertilization occurs and what stage of development is transferred, and to which location. IVF involves external fertilization and uterine embryo transfer, making it suitable for blocked fallopian tubes. ZIFT also involves external fertilization but transfers the resulting zygote into the fallopian tube, requiring patent tubes. GIFT, uniquely, facilitates internal fertilization by placing both eggs and sperm directly into the fallopian tube, thus also necessitating healthy tubes. These distinctions are crucial for understanding their indications and mechanisms.
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