Step 1: Ovarian Stimulation

Duration: 8-14 days

Injectable gonadotropins (FSH and/or LH) stimulate multiple follicles to grow simultaneously. Natural cycles produce 1 dominant follicle; IVF stimulation aims for 10-20 follicles. Monitoring involves serial transvaginal ultrasounds (every 2-3 days) and blood estradiol levels to track follicular growth and adjust medication doses.

• GnRH agonist (Lupron) or antagonist (Cetrotide/Ganirelix) prevents premature ovulation
• Estradiol typically rises 200-300 pg/mL per mature follicle
• Follicles are considered mature at 17-20 mm diameter
• Overstimulation risk (OHSS) increases with >20 follicles or E2 >3,000 pg/mL

Step 2: Trigger Shot

Duration: Single injection, 36 hours before retrieval

When lead follicles reach 18-20 mm, a "trigger shot" is administered to induce final oocyte maturation (resumption of meiosis). The timing is precise: retrieval must occur 34-36 hours later, before natural ovulation would occur.

• hCG trigger mimics the natural LH surge
• GnRH agonist trigger causes endogenous LH/FSH surge (lower OHSS risk)
• Agonist trigger requires modified luteal support
• Timing must be exact: too early = immature eggs, too late = ovulation

Step 3: Egg Retrieval

Duration: 15-30 minutes

Transvaginal ultrasound-guided aspiration of follicular fluid containing oocytes. A thin needle is passed through the vaginal wall into each ovary. Performed under conscious sedation or general anesthesia. Average retrieval yields 8-15 eggs depending on age and response.

• Not all follicles contain eggs; expected yield is ~75-80% of follicles
• Embryologist identifies and grades oocytes immediately
• Partner provides semen sample same day (or frozen sperm is thawed)
• Post-procedure: 1-2 hours monitoring, mild cramping/bloating expected for 2-5 days
• Serious complications rare (<1%): bleeding, infection, ovarian torsion

Step 4: Fertilization

Duration: Day 0-1

Mature (MII) oocytes are inseminated with prepared sperm. Two methods: conventional IVF (sperm placed around the egg in a dish, 50,000-100,000 motile sperm per egg) or ICSI (single sperm injected directly into the oocyte). Normal fertilization is confirmed by the presence of two pronuclei (2PN) at 16-18 hours.

• Typical fertilization rate: 60-80% of mature eggs
• ICSI is required for severe male factor, prior fertilization failure, or PGT
• Abnormal fertilization (1PN or 3PN) embryos are discarded
• Rescue ICSI can be attempted if conventional IVF shows no fertilization at 6 hours

Step 5: Embryo Culture

Duration: Days 1-5/6

Embryos are cultured in specialized media in incubators that maintain precise temperature (37°C), pH, humidity, and gas concentrations (5-6% CO2, 5% O2). Embryologists assess development at key checkpoints: 2-cell (day 1), 4-cell (day 2), 8-cell (day 3), morula (day 4), blastocyst (day 5-6).

• Day 3 transfer: 6-8 cell embryo (used less frequently now)
• Day 5 transfer: blastocyst stage (100+ cells) - allows better embryo selection
• Approximately 40-60% of fertilized eggs reach blastocyst stage
• Time-lapse imaging (EmbryoScope) allows continuous monitoring without disturbing culture
• Gardner grading system for blastocysts: expansion (1-6), ICM grade (A-C), TE grade (A-C)

Step 6: Embryo Transfer

Duration: 5-10 minutes

One (or rarely two) embryo is loaded into a thin catheter and placed into the uterine cavity under ultrasound guidance. The procedure is painless and does not require anesthesia. The decision to transfer fresh vs. frozen embryos depends on OHSS risk, PGT results, and endometrial readiness.

• Single embryo transfer (SET) is now standard of care for women <38
• Elective single embryo transfer reduces twin rate from ~30% to ~1-2%
• Full bladder improves ultrasound visualization
• Embryo is placed 1-2 cm from the fundus
• Bed rest after transfer is NOT shown to improve outcomes

Step 7: Luteal Support & Pregnancy Test

Duration: 9-12 days after transfer

Progesterone supplementation maintains the endometrial lining during the implantation window. Beta-hCG blood test at 9-12 days post-transfer confirms biochemical pregnancy. A value >50 mIU/mL with appropriate doubling (every 48-72 hours) is reassuring. Viability ultrasound at 6-7 weeks confirms clinical pregnancy (heartbeat).

• Beta-hCG < 5 = negative; 5-25 = indeterminate; >25 = positive
• Progesterone typically continued through 10-12 weeks gestation
• Chemical pregnancy (positive hCG that does not progress) occurs in ~10-15% of IVF transfers
• Ectopic pregnancy rate in IVF: ~2-5%

Long Agonist (Lupron) Protocol

GnRH agonist (Lupron) started in the mid-luteal phase of the prior cycle to suppress the pituitary (downregulation), followed by gonadotropin stimulation. This "long protocol" provides the most controlled stimulation and was historically the most common approach.

Best for: Young patients with normal ovarian reserve, PCOS (good response expected)

Antagonist Protocol

Gonadotropin stimulation begins on cycle day 2-3 without prior suppression. A GnRH antagonist (Cetrotide or Ganirelix) is added when the lead follicle reaches 13-14 mm (usually day 5-7) to prevent premature ovulation. Now the most commonly used protocol worldwide.

Best for: Most patients, especially OHSS-risk patients (allows agonist trigger), poor responders

Mini-IVF (Minimal Stimulation)

Uses lower doses of gonadotropins, often combined with oral medications (Clomid or Letrozole). Aims for 3-8 eggs rather than 10-20. Reduces cost and side effects but may require more cycles to achieve pregnancy.

Best for: Older patients, diminished ovarian reserve, patients wanting lower medication exposure, cost-conscious

Natural Cycle IVF

No stimulation medications; retrieves the single egg from the natural dominant follicle. Success rates are low per cycle but cumulative rates can be reasonable with multiple attempts. Sometimes modified with low-dose gonadotropins.

Best for: Patients who cannot tolerate stimulation, religious/ethical objections to creating multiple embryos, DOR patients who recruit only 1 follicle regardless

Dual Stimulation (DuoStim)

Two stimulation cycles within a single menstrual cycle: conventional follicular phase stimulation followed by a second stimulation in the luteal phase. Doubles the number of oocytes retrieved per calendar month.

Best for: Time-sensitive patients (cancer diagnosis), severely diminished ovarian reserve

PGT-A (Aneuploidy Screening)

Screens embryos for missing or extra chromosomes (aneuploidy). Identifies embryos with the correct number of 46 chromosomes (euploid) for transfer.

Accuracy: 98-99% for detecting chromosomal abnormalities | Method: Next-generation sequencing (NGS) of 5-10 trophectoderm cells biopsied from Day 5-7 blastocyst

Cost: $3,000-$6,000 per cycle (in addition to IVF cost)

Indications

• Maternal age ≥35 (aneuploidy risk increases exponentially)
• Recurrent pregnancy loss (≥2 miscarriages)
• Repeated implantation failure (≥3 failed transfers)
• Prior aneuploid pregnancy (e.g., trisomy 21)
• Severe male factor infertility
• Elective — to select the best embryo and reduce time to pregnancy

PGT-M (Monogenic/Single Gene)

Tests embryos for a specific known genetic mutation that runs in the family. Prevents transmission of serious genetic diseases to offspring.

Accuracy: >98% diagnostic accuracy for targeted mutations | Method: Customized probes designed for the specific family mutation + linked STR markers (haplotyping). Requires 2-4 weeks of test development before IVF cycle.

Cost: $5,000-$10,000 (including custom probe development)

Indications

• Both parents are carriers of autosomal recessive disease (CF, sickle cell, Tay-Sachs)
• One parent carries autosomal dominant disease (Huntington's, BRCA1/2, Marfan)
• X-linked conditions (Duchenne muscular dystrophy, hemophilia A)
• HLA matching for existing affected sibling needing stem cell transplant ("savior sibling")

PGT-SR (Structural Rearrangements)

Screens embryos from parents with known chromosomal structural rearrangements (translocations, inversions, deletions, duplications) to select balanced/normal embryos.

Accuracy: >95% for detecting unbalanced rearrangements | Method: NGS or array CGH to detect segmental imbalances resulting from meiotic segregation errors

Cost: $4,000-$8,000 per cycle

Indications

• Reciprocal translocations (most common — affects 1 in 500 people)
• Robertsonian translocations (affects 1 in 1,000 people)
• Inversions (pericentric or paracentric)
• Deletions or duplications
• Recurrent miscarriage with known structural rearrangement in either parent