Natural cycle in vitro fertilization (IVF) uses the body's natural fertility rhythms to determine the best time to implant a fertilized egg into the womb. This method may be preferable for some women because it avoids the use of fertility hormones like clomiphene, which can have difficult side effects. Natural cycle IVF is less expensive than using conventional IVF medications and carries a significantly smaller chance of conceiving multiples, but per-treatment success rates are lower. This option works best for women who have regular and predictable menstrual cycles.
The first step in the natural IVF process is tracking the menstrual cycle. This can be done using a fertility calendar or fertility software to predict the days that the woman has the greatest chance of conception. Women using this method should track their daily basal temperatures to aid in prediction. A woman reaches the height of her fertility at the point in her menstrual cycle when lutenin hormone reaches its peak.
Natrual cycle IVF uses the woman's own eggs for conception. Near the height of fertility, an obstetrician or fertility specialist will examine the woman to ensure that eggs are ripening properly in her ovaries. As ovulation approaches, the woman may undergo daily ultrasound procedures to detect the production of viable, mature eggs. If eggs are not developing, a doctor may administer follicle-stimulating hormone (FSH) or human chorionic gonadotropinn (HCG) to encourage production.
A woman will undergo egg harvesting once the fertility specialist has identified a ripened egg. Unlike IFV, when using drugs like clomiphene, a fertility specialist harvests only one egg per treatment. The eggs are usually removed from the ovaries in an office procedure using conscious sedation. The harvesting procedure is facilitated by a transvaginal ultrasound that helps the doctor locate the mature egg.
Aside from the timing of egg harvesting and implantation, natural cycle IVF uses processes similar to conventional IVF. After the egg has been harvested, it will be fertilized. If the egg develops into a viable embryo, it will be placed in the woman's uterus to grow. A pregnancy test administered two weeks after the egg is transferred to the womb will determine if the procedure has been successful.
Fertility clinics claim about a 35% success rate after embryo transfer with natural cycle IVF procedures. This does not account for patients that do not develop viable eggs during the course of treatment or for eggs that fail to fertilize. Some researchers indicate that the actual rate of delivery—when accounting for patients dropping out of the program, spontaneous miscarriage, and other factors—has about half the success rate of traditional IVF.
One of the limitations of natural cycle IVF is that implanting only one fertilized egg results in only one chance per treatment to conceive. This reduces the risk of multiple implantations, but may also increase the number of treatments necessary to successfully achieve pregnancy. Conventional IVF procedures may harvest many eggs at once that can be frozen and implanted at a later time. Women who chose natural cycle IVF will have to complete the entire harvesting procedure each time they wish to try to conceive.