Basic Principles of IVF

Understanding the Basic Principles of IVF

In vitro Fertilization (IVF) is one of the most common and highly-successful Assisted Reproductive Technologies utilized today to help women overcome conception difficulties. To understand how IVF works, we start with the basics of natural conception and then explore how IVF treatment can help to overcome obstacles that are inhibiting conception. Please note that the results of the infectious disease screening tests must be available prior to starting stimulation in anticipation of IVF. (See Evaluation & Testing for details.)

Natural Conception

In natural conception, fertilization takes place in the fallopian tube. In fact, the fallopian tube has three specific functions:

  1. it must pick up the ovulated oocyte
  2. it must provide a good environment for fertilization to occur and
  3. it must transport the resulting embryo to the uterus, so that implantation can take place.

When the fallopian tube is not functional or other impediments to fertility are present, the function of the fallopian tube can be substituted by IVF.

IVF Overview

The three basic principles of IVF are: Removal of eggs from the ovary, their fertilization in the laboratory, and subsequent placement of the resulting embryos in the uterus.

Ovarian Stimulation & Egg Retrieval

Most commonly, the ovaries are stimulated with injectable fertility medications, so that multiple eggs are available at the time of retrieval. (Specifics are provided in the IVF Cycle Detail section.) During the egg retrieval procedure, ultrasound is used to guide a hollow needle directly into each follicle. The liquid which surrounds each egg is then sucked out (“aspirated”). This procedure is called an “aspiration”. The fluid is carried to the laboratory, where the egg is isolated from the remainder of the fluid and placed in a dish filled with nutrient media for the purpose of fertilization.

Fertilization and ICSI

Eggs are combined with sperm in the laboratory by adding sperm to the dish containing the egg. In cases of severe male infertility, the sperm may not be able to penetrate the egg and therefore a procedure called “intra-cytoplasmic sperm injection” (or ICSI) must be utilized. In this procedure, each egg is picked up by a holding pipette and then is injected with one sperm. Fertilization by ICSI is not as efficient as conventional insemination in which the sperm are simply added to the egg, but it is an excellent way to achieve fertilization in cases where conventional insemination would surely fail.

Embryo Transfer & Luteal Phase Support

Following successful fertilization of the eggs, the resulting embryos are maintained in the laboratory for a variable period of time before being replaced in the body. Most commonly, embryos are placed in the uterus after three days of culture in the laboratory. In the case of blastocyst transfer, the embryos are maintained in the lab for five or six days. If tubal embryo transfer is planned, the embryos are placed in the fallopian tube 24 to 48 hours after aspiration.

Embryos are most commonly placed into the uterine cavity by trans-cervical transfer. This procedure is similar to an intra-uterine insemination (IUI) in that a catheter is used to negotiate the cervix and to place the embryos in the uterus. The embryos are maintained in the uterine cavity by surface tension.

The embryo transfer process is critical to the success of all high-tech fertility procedures. Even perfect quality embryos placed into a perfectly prepared uterus may fail to implant during an IVF cycle if they are not placed in a correct location or if a uterine contraction (cramp) causes the transferred embryos to move from their proper location. The doctors of USC Fertility are experts at this delicate, yet critical procedure. Furthermore, our program uses the full-bladder technique to help straighten the uterine axis, a special soft catheter to minimize trauma to the uterus and simultaneous ultrasound to visualize the correct placement of the transferred embryos. The embryo transfer is always practiced at least twice: once at the time of egg retrieval or at the time of endometrial biopsy for recipients of egg donation, and a second time just before embryo transfer is achieved. In rare instances, we may recommend a tubal embryo transfer.

We are very much aware of the critical nature of this essential part of the fertility process and are always working toward attaining the highest possible success.

Luteal Phase Support with Progesterone Supplementation

In most instances, progesterone supplementation is used after embryo transfer – during the ‘luteal phase’, or second half of a woman’s cycle, to help ready the endometrium to receive an embryo for implantation. The most common dose is 200 mg vaginally twice daily. The progesterone is continued until the end of the first trimester if the pregnancy is successful, or until the second negative pregnancy test.