What are the different types of In Vitro Fertilization (IVF)?

Types of In Vitro Fertilization (IVF)

IVF encompasses several distinct technical approaches, with conventional IVF (c-IVF) and intracytoplasmic sperm injection (ICSI) being the two primary methods, alongside specialized variations including in vitro maturation (IVM), embryo cryopreservation, and oocyte cryopreservation. 1

Primary IVF Techniques

Conventional IVF (c-IVF)

• In conventional IVF, retrieved oocytes are placed together with prepared sperm in culture medium, allowing natural fertilization to occur outside the body. 2
• This technique involves ovarian stimulation with follicle-stimulating hormone (FSH) for approximately two weeks from the onset of menses, followed by ultrasound-guided transvaginal oocyte retrieval under intravenous sedation. 3
• For couples with non-male factor infertility, conventional IVF should be the preferred method over ICSI, as it achieves higher implantation rates (30% vs 22%) and requires significantly less laboratory time (23 minutes vs 74 minutes). 4
• The fertilization rate with c-IVF is approximately 92.6% in appropriate candidates. 5

Intracytoplasmic Sperm Injection (ICSI)

• ICSI involves direct injection of a single sperm into each mature oocyte using micromanipulation techniques, originally developed for severe male factor infertility. 2, 6
• ICSI should be reserved specifically for severe male factor infertility, particularly when pre-wash total motile sperm count (TMSC) falls below 3 million. 3
• For men with low TMSC, ICSI overcomes male factor infertility issues that would prevent successful conventional IVF. 1
• Despite widespread use, ICSI offers no advantage over conventional IVF in non-male factor cases and may produce lower rates of high-quality embryos (52.7% vs 63.3%). 5, 4, 7

Specialized IVF Variations

Single Embryo Transfer (SET) vs Multiple Embryo Transfer

• IVF with elective single embryo transfer (eSET) has become increasingly preferred to minimize multiple pregnancy rates while maintaining acceptable pregnancy rates. 3
• When IVF-eSET achieves ongoing pregnancy rates exceeding 38%, it becomes the preferred treatment over intrauterine insemination with ovarian stimulation (IUI-OS). 3
• Single embryo transfer should be strongly considered in patients with tubal factor infertility to minimize ectopic pregnancy risk, which increases up to 20-fold with multiple embryo transfer. 8

In Vitro Maturation (IVM)

• IVM involves retrieving immature oocytes and maturing them in laboratory conditions before fertilization, providing an alternative for patients with specific fertility challenges or limited egg availability. 1
• This technique avoids the need for extensive ovarian stimulation protocols required in conventional IVF. 1

Modified Natural Cycle (MNC) IVF

• MNC-IVF involves minimal or no ovarian stimulation, retrieving the naturally developing oocyte(s) during a woman's regular menstrual cycle. 3
• This approach reduces medication costs and multiple pregnancy risks but typically yields fewer oocytes per cycle. 3

Fertility Preservation Techniques

Embryo Cryopreservation

• Embryo cryopreservation is the most established fertility preservation method, involving conventional IVF followed by freezing of fertilized embryos for future use. 3
• This technique has been highly successful in women under 40 years of age. 1
• The process requires approximately 2-6 weeks delay in cancer treatment if performed before oncologic therapy, depending on timing within the menstrual cycle. 3

Oocyte Cryopreservation

• Oocyte (egg) cryopreservation involves ovarian stimulation and retrieval followed by freezing of unfertilized eggs, suitable for women without partners or those who prefer not to create embryos. 3, 1
• The American Society of Clinical Oncology recommends this technique for fertility preservation before cancer treatments. 3, 1

Ovarian Tissue Cryopreservation

• This experimental technique involves surgical removal and freezing of ovarian tissue for later reimplantation. 3, 1
• It may be considered when time constraints prevent standard ovarian stimulation protocols. 3

Important Clinical Considerations

Common pitfalls to avoid:

• Do not use ICSI routinely for non-male factor infertility—it provides no benefit and increases costs without improving outcomes. 4, 7
• Above a pre-wash TMSC of 3 million, conventional IVF is more cost-effective than ICSI; below 3 million, ICSI becomes necessary. 3
• ICSI raises unresolved concerns regarding gamete selection, potential damage, and offspring health conditions. 6
• Despite no evidence of increased congenital abnormalities, ICSI may be associated with higher rates of major birth defects compared to unassisted conception. 3

Patient age significantly impacts all IVF techniques, with fertilization rates correlating inversely with maternal age (r = -0.13, P < 0.006). 5