An overview of in-vitro fertilization (IVF)

IVF is a good starting point to understand assisted reproductive technology (ART). Other ART procedures are variations of the IVF “theme”.

Normally it takes the time of two menstrual cycles (two months) to complete one cycle of IVF.

If pre-implantation genetic test for aneuploidy (PGT-A), i.e., “counting embryo’s chromosomes”, is planned, one more month is needed. 

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Ms. Santos is in a new relationship. She wishes for pregnancy but had a tubal ligation. She is here to find more information about IVF, such as cost, treatment duration, time commitment, likelihood of success.  

I told her it usually takes two months: payment and tests in the first month, and IVF, in the following month (or a few months later). It consists of the following parts: baseline ultrasound/IVF start, stimulation/monitoring/trigger, egg retrieval, embryo transfer, and pregnancy test. 

Cost 

Each clinic has its own fee schedule. Typically, the fees cover three areas: laboratory (which handles eggs, sperm, embryos), provider (i.e. physician who oversees the whole IVF process, retrieves eggs from the ovary, and transfers embryos to the uterus), and medication (to stimulate the ovary so it produces as many eggs as possible within safety). Each area makes up roughly a third of the total cost. 

Clinics collect the fees of the first two areas; patients are responsible for the medication. The fees may be fully, partially, or not covered by the patient’s medical insurance. So is the cost of medication by patient’s prescription plan. To reduce medication cost, some clinics help patients obtaining medication from out of the country. It is legal but takes more time. 

There may be added cost if PGT-A is planned. The fees have two parts: one is payable to the IVF laboratory (that biopsy the embryos), the other, to the outside laboratory that counts the chromosomes. Insurance may or may not foot the bill. 

Preparation (blood and other tests) 

This takes about one month (one menstrual cycle). It can be performed the month before the IVF treatment or a few months prior so as to collect and evaluate test results.  Below is a partial list. 

• Menstrual cycle day 3 antral follicle count (AFC), and estradiol, FSH, and anti-Mullerian hormone (AMH).  

• Infectious diseases, including syphilis, HIV, hepatitis B and C 

• Antibodies against Rubella (German measles) and Varicella (chicken pox) 

• Liver, kidney and thyroid function, blood group (ABO) and type (Rh), and blood count 

• Evaluation of the uterine cavity by one of the following methods, Sono-hysterogram (SHG), hystero-salpingogram (HSG), office hysteroscopy, or conventional hysteroscopy in the operating room 

• Pap smear 

• Semen analysis (sometimes a frozen sample as a backup) 

• Carrier screening for recessive-gene diseases (optional) 

• Deciding on whether to have PGT-A (optional). 

Some of the above are self-explanatory; others may not be so obvious. Some are explained briefly here. More detailed discussions will appear in future posts.   

Menstrual cycle day 3 blood tests are designed to assess the “ovarian reserve”. Providers use the results to make an educated guess about the regimen and the strengths of each medication (the “stimulation protocol”). It is hoped that such a regimen enables the ovaries to produce the highest number of eggs. The first day of full flow is counted as day 1. Some providers take results from days 2, 4 or 5.  

German measles causes deformities in the fetus; pregnant women are at high risk to die when contracting chicken pox. Immunity against German measles and chicken pox protects the fetus and the mother, respectively. Women can be vaccinated if they are not immune.  

Uterine cavity assessment ensures the best environment for implantation. In addition, the condition of Fallopian tubes may be assessed simultaneously. Fluid in the Fallopian tube (hydrosalpinx) hinders implantation.  

Carrier screening tests help us finding individuals who are carriers of disease(s) caused by recessive-gene(s) - cystic fibrosis is a good example. Blood test is the only method to find carriers, because they cannot be distinguished from true normal individuals.  

PGT-A uses molecular biology technology to “count” the chromosomes of embryos. Normal embryos have 46 chromosomes, twenty-three from each parent. Embryos with anything but 46 chromosomes have low chance of implantation. Even if they do implant, there is high probability of miscarriage. Rare live births are associated with multiple problems. One such example is Down’s syndrome; afflicted individuals have 47 chromosomes. 

Stimulation (i.e. ovulation induction), monitoring and trigger 

Most protocols use menstruation as a reference point to begin stimulation (i.e. to begin medication). Birth control pills may be used to delay the start for logistical or other reasons. If an individual does not have predictable menstruation (such as individuals with PCOS), the menstruation may be induced by Provera. 

Baseline ultrasound is a safety check before stimulation. The rule of thumb is all cysts (follicles) in the ovary are < 10 mm. Some providers have a higher threshold, 15 mm. 

Two or three medication is used daily typically. Almost all are delivered by sub-cutaneous injections using very fine needles. Pain from the needle is a rare complaint. The time of injections, usually in the evening, should be constant. But, one- or two-hours deviation does not matter that much.  

Monitoring ensures best response (and prevents complications such as ovarian hyper-stimulation). Blood test (estradiol) and trans-vaginal ultrasound (size and number of follicles) are performed. The former assesses the biochemical response of the ovaries, the latter, the physical response. Dosage adjustment may be necessary. 

The first monitoring visit is normally after three days of injections. Later visits are normally every two days. The stimulation takes 10 to 12 days – sometimes longer. Patients are usually asked to come as early as 7:00 AM to ensure results are available before noon. The visit usually takes an hour or less. 

The final step of stimulation is “trigger”. The “trigger shot” matures the eggs, making them fertilizable by the sperm. The trigger shot is usually a subcutaneous injection, to be given at a specific time, such as 9:00 or 11:30 PM. It is decided based on the time of planned egg retrieval, typically 36 hours prior. The time to inject the trigger shot is very critical. It needs to be strictly adhered to. More information about trigger may be seen in my prior post. 

Egg retrieval 

Egg retrieval is performed under I.V. general anesthesia. The anesthetics are delivered through the I.V. line. Occasionally, a plastic device is placed in the mouth to help breathing. The follicles are punctured by a needle passing through a guide attached to the trans-vaginal ultrasound probe. So far, I have not heard patients complain of pain during the retrieval (or throat pain after the retrieval). As general anesthesia is used, patients do not eat or drink after midnight the night before. Retrieval takes place as early as 7:00 AM. 

Pelvic pain after the retrieval is due to bleeding from multiple sites of follicle punctures. It is similar to ovulation pain, which is caused by bleeding from the ovulation site. On the night of retrieval, most people do well. Some need Ibuprofen or Tylenol; few need stronger pain medication, such as hydrocodone. Almost all said they were able to resume normal duties the day after. 

Unless frozen sperm is used, the male partner is asked to produce a fresh sperm sample while the retrieval is taking place. Whereas male partners may not have to come in other visits, egg retrieval is the visit that he is absolutely needed. He produces fresh semen and serves as a designated driver. 

Fertilization 

The eggs stay in the incubator for four to six hours before receiving sperm. The traditional way is insemination, where sperm is added to the culture medium. Nowadays, intra-cytoplasmic sperm injection (ICSI) delivers one sperm to each egg by injection. Either way, fertilization of eggs is examined the following morning. 

Normally, embryologists make embryos from all eggs and freeze unused embryos for the future. Sometimes, patients request to freeze some eggs for religious or other reasons. Due to attrition (more below), this is not practical when fewer than eight or six eggs are retrieved. 

Embryo transfer (fresh embryo transfer, no PGT-A) 

If no test is planned on the embryos, they may be put back to the uterus five days after retrieval. This procedure is embryo transfer. Most embryos develop to blastocyst stage by this time; they are called blastocysts. Sometimes they are called “day 5 embryos”. Occasionally, embryos are transferred three days after retrieval, at six to eight cell stage. 

Embryo transfer is performed under real-time, trans-abdominal ultrasound. It is not painful. Patients come with a partially full bladder so the uterus may be visualized by the ultrasound. A catheter is placed inside the uterus to deliver the embryo(s). It is like intrauterine insemination. 

Air bubbles and embryo(s) are placed inside the catheter to aid visualization - embryos are microscopic but air bubbles appear as bright spots on ultrasound. Once air bubbles are seen inside the uterus, it can be assumed that embryos are also inside the uterus. The assumption is valid once the embryologist checks the catheter, confirming no embryos are still in the catheter. This completes the transfer procedure. Patients may empty their bladders now. 

Later on, remaining blastocysts are frozen. Embryologists check and freeze more blastocysts one day later, six days after egg retrieval. 

Pregnancy test 

Pregnancy test is performed ten days after embryo transfer. This is usually about 30 days from the beginning of stimulation. If a blood hCG is performed, the level ranges from 50 to 200 mIU/mL. 

Embryo transfer (frozen embryo transfer, when there is PGT-A) 

If PGT-A is planned, there will be no embryo transfer five days after egg retrieval. Instead, the embryos are biopsied and frozen (kept in liquid nitrogen) individually. Once the PGT-A results are available, the normal ones can be used. This is called frozen embryo transfer, and usually takes place after the next menstruation. The procedures are the same as fresh embryo transfer. 

Embryo biopsy for PGT-A 

Embryo biopsy normally takes place five days after retrieval (sometimes after six days). The embryos have 150–200 cells, divided into outside and inside cell groups. They are called trophectoderm and inner cell mass, respectively. The former develops into the placenta, and the latter, the fetus. Both are stem cells, capable of replenishing themselves. Five to eight cells are removed from the outside cell group and sent to a laboratory to “count” the chromosomes. 

The PGT-A results usually are available in 10 days, when the menstruation begins. Once menstruation begins, it takes 21 – 25 days to prepare the uterus. Pregnancy test is 10 days after embryo transfer. 

Probability of live birth (IVF success) 

The Center of Disease Control (CDC) publishes national IVF results every year based on data collected from all IVF clinics across the country. It is a good resource for potential IVF patients. (https://www.cdc.gov/art/artdata/index.html)

The report by the CDC tabulates IVF success based on why an individual needs IVF (for example, male factor, endometriosis...etc.). Different diagnoses have different impacts on IVF success. In addition, advanced age and higher body weight are associated with lower success. The table below shows the impact of age on IVF success regardless of diagnosis (2020 data). (https://nccd.cdc.gov/drh_art/rdPage.aspx?rdReport=DRH_ART.ClinicInfo&rdRequestForward=True&ClinicId=9999&ShowNational=1) 

The CDC website also has an “IVF success estimator” (below). It calculates the probability of having a live birth based on age, body weight, and diagnoses (i.e. the reason for IVF treatment). It is good to know that the estimator provides the probability for a group of individuals with the same conditions. It is a good reference; individual’s outcome is likely to vary. (https://www.cdc.gov/art/ivf-success-estimator/index.htmlhttps://www.cdc.gov/art/ivf-success-estimator/index.html)

Attrition   

Attrition is another important concept in IVF. Reduction occurs at every step along the timeline of IVF treatment. The number of follicles is almost always higher than the number of eggs retrieved. Not all eggs are mature, and, therefore, only a fraction of retrieved eggs can be fertilized. On average, 70% eggs become fertilized, 50% fertilized eggs develop to blastocysts, and 50% blastocysts have 46 (normal) chromosomes. 

Update 1: A link to CDC ART report was added on 1/5/2024