Parenting Australia

Assisted Conception

All women are born with a finite number of eggs. Each woman is genetically predetermined as to when those eggs will run out and for each woman this end point will be different. However, in general fertility starts to decline after the age of 35 and pregnancy rates are extremely low by the mid forties.

Other causes of reduced fertility are ovulation disorders, endometriosis, blocked fallopian tubes, uterine anomalies and uterine polyps and fibroids. Male issues relating to sperm quality can affect a third of couples. Just one of these factors on its own, if mild, won't necessarily stop a pregnancy from happening but it could take a lot longer than normally expected. However, the negative effects on fertility are multiplied if more than one abnormality is present.

Assisted conception can increase the chance of pregnancy in two ways; first, by increasing the number of eggs available for fertilization and second, by increasing the number of sperm that get to where the egg is. In vitro fertilization (IVF) means fertilization of eggs in the laboratory. Follicle stimulating hormone (FSH) is used daily by injection to recruit as many follicles as possible in one cycle. As a woman ages there are fewer numbers of follicles left in the ovaries and no amount of FSH will stimulate more follicles than are available to be recruited. The ovaries response to the injection is monitored by several ultrasounds to measure the growth of the follicles. Usually it takes 11 to 14 days for the follicles to develop and they need to reach a size of 18mm to reliably produce fertilizable eggs. In order to grow the follicles, normal ovulation needs to be suppressed and this is done with a second drug either started before the stimulation begins (agonist cycle) or introduced in the middle of the cycle (antagonist cycle). When the follicles are ready a trigger injection of Human chorionic gonadotropin (hCG) is given to set into motion everything that will make ovulation happen, causing the egg in the mature follicle to be fertilizable and loosening it from the wall of the follicle so that it comes out at egg collection.

The eggs are retrieved transvaginally under ultrasound guidance. Either a general anaesthetic or sedation is used to minimize discomfort. The egg is found within the fluid aspirated from each follicle. The egg is fertilized with the sperm in one of two ways. In conventional IVF sperm are left in a plastic dish with the eggs and a random sperm penetrates each egg. If the sperm is suboptimal then a single sperm can be injected directly into each egg. This process is called Intracytoplasmic sperm injection (ICSI).

The subsequent embryos that develop are transferred to the uterus either on day 2 ( 2 to 4 cell stage), on day 3 ( 4 to 8 cell stage) of day 5 ( blastocyst stage). The day of transfer is based on the quality and number of embryos available. Progesterone in the form of a vaginal pessary or gel is given over the next several weeks to support the uterine lining and keep it receptive for pregnancy. Any surplus embryos which are good enough are frozen for future use.

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