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Natural Cycle IVF (nIVF)

Definition - What does Natural Cycle IVF (nIVF) mean?

Natural cycle IVF is a fertility treatment similar to traditional or stimulated in vitro fertilization, but avoids the use of high-dose medications to stimulate the ovaries to produce multiple eggs. The unstimulated, natural cycle IVF is typically used due to its ease and limited side effects. However, it carries a significant risk of a premature rise in the levels of luteinizing hormone (LH) prior to the egg retrieval, often resulting in the cancellation of the IVF cycle.

FertilitySmarts explains Natural Cycle IVF (nIVF)

A natural cycle IVF (nIVF) follows the pattern similar to that of a normal monthly menstrual cycle where several ovarian follicles develop but only one grows to its maximum size to release a single mature egg (i.e. ovulate). This means it is important to track the growth of the follicle so that ovulation does not occur before the egg retrieval is performed. While the tracking can be done via ultrasound and measuring the LH levels, the process entails intensive monitoring and around-the-clock service, which most laboratories are unable to provide. LH levels can surge before time causing premature ovulation and failure to retrieve the one and only available egg afterward. The planning of egg retrieval based on an LH rise then results in cancellation of the natural IVF cycle.

The availability of one egg and only one embryo implies that no embryos can be frozen for a future attempt in case the present natural cycle IVF is unsuccessful. The cumulative success rate of a natural cycle IVF is barely 50% versus 96% following a single traditional IVF cycle. However, the use of anti-inflammatory medications called nonsteroidal anti-inflammatory drugs (aka NSAIDs) has shown to improve the success rate of a nIVF by postponing the rupture of the dominant follicle, reducing the frequency of unwanted premature ovulation, and boosting the percentage of cycles reaching embryo transfer.

Despite the pitfalls of the procedure, the natural cycle IVF is simple, rapid, and does not put a woman at risk of overstimulation of the ovaries due to the avoidance of the high-dose medications to stimulate the ovaries. This is in contrast to a stimulated cycle where ovaries are prone to overstimulation and the resulting complications. A natural cycle IVF also prevents multiple pregnancies and the associated risks.

Natural cycle IVF may be desirable in advanced-age women who have encountered repeated failures with stimulated IVF cycles. A small number of studies show promise in retrieving a mature egg in these women when a hormonal medication called GnRH analog (Gonadotropin-releasing hormone) is used to stimulate the final egg maturation. Although not completely natural, the procedure can enable timely LH surge, ovulation, and egg retrieval.

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