time to transfer #3 in vitro fertilization Flashcards
interactions involving parts of the brain (the hypothalamus and anterior pituitary gland) and the reproductive tract (the ovaries and the uterus).
The hypothalamus is responsible for initiating and controlling a lot of important bodily functions, such as regulating body temperature, controlling your appetite, and releasing hormones that affect many of the body’s organs, including the ovaries. The hypothalamus does the latter by producing a hormone called gonadotropin-releasing hormone or GnRH. Based on its name, you’d expect this hormone to alter the function of gonadal tissue, which it does through an intermediary, the anterior pituitary. In response to the hormone from the hypothalamus, this part of the pituitary gland releases two hormones that affect the ovaries. One of these hormones is follicle-stimulating hormone or FSH, and the other is luteinizing hormone or LH. Together they promote the cyclic alterations in both the structure and function of the ovaries that will be important for in vitro fertilization to have a chance to be effective.
FSH
During the early phase of the menstrual cycle, secretion of FSH exceeds that of LH. The simplest way to remember this is to think about what the name FSH means – follicle stimulating hormone. Follicles are small sacs in a woman’s ovaries that initially contain immature eggs. In response to increasing concentrations of FSH during the early part of the cycle, the follicles increase in size and the egg inside them begin to mature. At just the right time, the concentration of LH exceeds that of FSH, and one of the mature follicles releases its egg from the surface of the ovary into a small tubule that leads to the uterus. This is known as ovulation. Under normal conditions that result in a pregnancy, this mature egg would enter the uterus where it would be fertilized by sperm; well technically, a single spermatozoon.
FSH injections
one goal is to have more than one egg mature simultaneously. This is achieved by administering FSH to the woman via a series of daily injections, with the amount of FSH used being higher than the concentrations normally produced by the anterior pituitary. To determine whether or not the desired effects are being achieved, growth of the follicles can be monitored using ultrasound.
LH-similar injection
When the desired number of follicles are maturing, a compound very similar to LH will be injected to loosen each egg from the wall of its follicle. With the patient sedated a day or so later, the fluid inside each follicle will be aspirated using a fine needle passed through the vaginal canal and into each follicle. This procedure is done using ultrasound to guide the needle into each follicle. The fluid then is examined using a microscope and the eggs will be retrieved.
mixing eggs with sperm
Typically, the eggs and sperm are incubated overnight and examined the following days for evidence of fertilization. About 70% of the eggs will become fertilized and develop into embryos, assuming both the eggs and sperm appear to be normal. Under normal conditions, a few days later an embryo will be transferred into the uterus through a thin catheter passed through the cervix. The other embryos can be stored frozen for future use.
after the eggs are fertilized
they are allowed to progress to the blastocyst stage, which is comprised of more than 100 cells. There are two different types of cells located deep to the rather thin outer zona pellucida layer. The two types of cells include those of the ‘inner mass’ that eventually will develop into the fetus, and the trophoectoderm cells that will form the inner lining of the placenta. A few of the trophoectoderm cells are aspirated and submitted for genetic analysis. Because these cells contain the same DNA as the inner mass cells, analyzing trophoectoderm cells provides the information needed to determine whether the developing embryo and eventually the baby will have mutation for the hemoglobin gene. Most importantly, removal and analysis of a few of these cells will provide this information while leaving developing embryo untouched
last step before embryo transferred to uterus
the laboratory will have developed small fragments of DNA, commonly called ‘probes’, that match the mutation in the hemoglobin gene. These DNA fragments will be used to identify embryos that either have or lack the mutated gene. An embryo lacking the mutation will be selected, transferred into the uterus, where it will develop without either the sickle cell trait or any chance of developing sickle cell anemia. In this way, you can eliminate the possibility of your offspring ever having to worry about this condition.
