Definition and types

By assisted fertilization in humans we understand the use of manipulation methods on one or both gametes in order to achieve a pregnancy, regardless of the cause of infertility and the degree of manipulation.

We believe this could be a useful classification.

In vivo fertilization:

  • Artificial Insemination by Husband’s Sperm (AIH).

  • Artificial Insemination by Donor’s Sperm (AID).

  • In vitro fertilization.

By type of transfer:

  • Transcervical, intrauterine.

  • Gamete intrafallopian transfer (GIFT).

  • Zygote intrafallopian transfer (ZIFT).

  • Tubal embryo transfer (TET).

By type of insemination:

  • Spontaneous or conventional.

  • Intracytoplasmic sperm injection or microinjection (ICSI).


  • Preimplantation diagnosis.

  • Frozen embryo transfer.

  • Oocyte donation.

Artificial insemination with husband’s sperm (AIH).

Artificial insemination with husband’s sperm is one of the most common techniques. The technique consists of depositing some sperm, which has been prepared in the laboratory by using techniques aimed at improving quality, preferably in the uterine cavity.

The most common indications are:

  • Inability to ejaculate in the vagina (psychogenic or organic impotence, severe hypospadias, retrograde ejaculation and vaginal dysfunction).

  • Infertility due to male factor, in which there is a deficit in the number, motility or morphology of sperm.

  • Cervical factor.

  • Immune or unexplained infertility.

Artificial insemination with donor’s sperm (AID).

  • Male Factor not suitable for ICSI.

  • ICSI failure.

  • Hereditary disease in men.

  • Women with no partners.

  • Protected intercourse with HIV-positive male.

  • Rh isoimmunization.

In vitro fertilization (IVF).

IVF consists of facilitating the fusion of sperm and egg in a dish in the laboratory, outside the human body. If fertilization occurs within the first 48 hours, the embryos are transferred to the uterine cavity through the cervix between 2 and 6 days after fertilization.

When the tubes of the patient are normal, transfer through them has been advocated, either of gametes (sperm and oocytes), which we call GIFT, zygotes (ZIFT) or embryos (TET). These alternatives are not commonly used nowadays, since they are not more effective than transcervical transfer, but should be considered in cases of difficulty in the cervical canal and even for religious reasons (the Catholic Church authorizes GIFT).

IVF is indicated for:

  • Tubal pathology.

  • Endometriosis.

  • Esterilidad masculina ( pero con más de 5 millones por ml).

  • Immune infertility.

  • Infertility without a cause.

  • Any cause of infertility whose initial treatment has failed.

Intracytoplasmic sperm injection (ICSI).

Several procedures have been developed along the last 6-7 years which are aimed at solving the problem of severe male infertility by means of micromanipulation and microinjection of a single sperm cell into the cytoplasm of the oocyte (ICSI), which has emerged as a technique to solve these cases.

ICSI can be carried out with ejaculated sperm or that obtained by microepididymal sperm aspiration (MESA) or testicular sperm aspiration (TESA) from a biopsy. They will be discussed in detail in the corresponding section.

Embryo cryopreservation.

Cryotechnology is a necessary part of IVF programs in order to avoid the risk of multiple pregnancies resulting from the transfer of large numbers of embryos as well as to avoid having to dispose of surplus embryos from large cohorts of oocytes. Today it is a routine procedure that increases the IVF process cumulative pregnancy rate.

It is indicated for:

  • Preserving surplus embryos of IVF as only a limited number are transferred in order to avoid multiple pregnancies.

  • Preserving embryos biopsied during genetic preimplantation diagnosis.

  • Preserving all frozen embryos in the event of serious hyperstimulation risk so that they can be transferred in the next cycle or because the woman will be subjected to a therapy which will result in her ovarian function to stop.

  • Assisting to embryo donation with 2 purposes:

    • Avoid synchronization between donor and recipient.
    • Maintain quarantine until HIV negativity has been confirmed.

Oocyte donation.

As a result of certain social and employment reasons, women delay the time of conception and after the age of 40 we find a decrease in fertility due to various factors: reduced embryo implantation capacity, a higher rate of abortions and an increased occurrence of genetic abnormalities.

This means that in many cases only egg donation can be offered as an assisted reproduction technique.

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