How Does Egg Freezing Work?

The process of freezing your eggs is broken into two steps. The first step is when you initially freeze your eggs or embryos, and the second step is thawing and implanting the eggs or embryos. Here’s what you can expect:

Part 1: Egg/Embryo Freezing and Storage

Initial Consultation

The first step is to set up a consultation. The doctor will assess your fertility potential and discuss your options. This is a good time to decide whether egg freezing or embryo freezing is a good option for you. This initial workup will typically include some blood tests and an ultrasound screening to determine your ovarian reserve.

We check hormones like TSH, T4, Prolactin, Free Testosterone, and DHEAS. Also included is testing for HIV 1, 2, Hepatitis B, C, RPR, blood type, Rubella, and a genetic screen. We also include a blood test called AMH. This blood test will help assess your ovarian reserve and will give us some guidance for the amount of stimulation you will require, along with preliminary information about the number of eggs we may obtain.

Ovarian Stimulation

During the ovarian stimulation process, you will receive daily injections of follicle-stimulating hormone (FSH), and Menapur (FSH, LH) to facilitate the development of multiple eggs in the ovaries, so more than one egg will be available for freezing. Patients typically come to the office 3-5 times for ultrasounds, blood work, and monitoring during this 10-14 day period.

Egg Retrieval

Prior to and during the retrieval, the patient is given intravenous sedation by an anesthesiologist. The egg retrieval is performed using a transvaginal ultrasound for visualization of the follicles and a long needle to aspirate the eggs out of the follicles through the wall of the vagina. The eggs are then passed to the embryologist in tubes containing culture media. The procedure requires approximately 15-30 minutes and patients are monitored for approximately 1 hour to ensure safety.

Egg/Embryo Freezing and Storage

If you choose to freeze embryos, then your eggs will be fertilized with your partner’s sperm soon after retrieval and allowed to grow in a petri dish for a few days before they are frozen. If you decide to freeze your eggs, then they are frozen immediately after the retrieval.

The entire freezing process takes about two months. Depending on the number of eggs or embryos that you and your doctor decide to freeze, you may need to undergo more than one egg freezing cycle.

Fertilization Process

Fertilization of the Eggs to Embryos

For women who have frozen eggs, the eggs will go through a special thawing process and will be prepared to be fertilized into embryos. For women who elect to freeze embryos, they will immediately go through the fertilization process. The fertilization process happens when the embryologist receives the eggs, removed them from follicular fluid, and places them in the appropriate media to complete their maturation. After about four hours, the eggs are placed with the sperm, fertilization occurs, and the eggs are placed in an incubator. If injection of the sperm into the egg (ICSI) is indicated, it will be performed at this stage.

Day 1 after Eggs have been Fertilized

Approximately 24 hours after the retrieval, the eggs are checked to see if they fertilized properly and if development of the embryo (fertilized eggs) has begun. The embryos are allowed to develop inside of the incubator for 3-5 days after the retrieval. Incubators control environmental conditions such as temperature, air quality, acidity, and several other factors that may influence the embryos’ development.

Embryo Development

Embryos between day 1 and 3 after retrieval are called “cleavage-stage embryos.” On day 5, the embryos are called “blastocysts.” In some cases, embryos are cultured until day 6. The extended culture of embryos assists in selecting the best embryos for a transfer and limits the number of embryos placed into the uterus to decrease the chance of multiple pregnancy. If an embryo biopsy is desired, it will occur on day 5 or 6.

Part 2: Thawing and Preparing for Pregnancy

Preparation for Pregnancy

Once you are ready to try to become pregnant, you’ll begin a cycle of medication to prepare your uterus. Your doctor may choose to prescribe Lupron or Cetrotide to reduce the chances of ovulation occurring unexpectedly. You’ll also receive estrogen and progesterone medications.

You work closely with your doctor to ensure the process goes as smoothly as possible. At this time, you and your doctor will decide whether to have genetic testing performed on the embryos, along with how many embryos to transfer.

Embryo Transfer

This brief procedure uses an abdominal ultrasound to place the embryos about 1.5 cm from the top of the uterus. You’ll need to keep taking medications to help support the uterus during the early stages of your pregnancy, and your doctor will determine when it is safe for you to stop taking those medications. You will come in for a pregnancy test about 12 days after the embryo transfer, and your doctor will determine if you are pregnant.