The first successful pregnancy and live birth resulting from
IVF were achieved during an unstimulated natural cycle
(1). Soon thereafter, natural IVF was replaced by stimulated
IVF because of the very high cancellation rates of natural
cycles, and stimulated treatment became the standard in
IVF. However, ovarian stimulation is not free from negative
consequences and risks, including ovarian hyperstimulation
syndrome. (OHSS), which affects up to 5–10% of IVF cycles
and can be life-threatening (2). Multiple pregnancies occur
in approximately 30% of pregnancies in patients who undergo
the COH protocol and this phenomenon is related to increased
risks of pregnancy loss, obstetrical complications,
prematurity and neonatal morbidity with long-term damage.
The long-term side effects however remain largely unknown.
Ovarian cancer and gestational trophoblastic disease may be
associated with the chronic use of gonadotrophins (3). Nevertheless,
the interest in natural IVF cycle treatment has
been renewed in recent years because of the increased efficiency
of IVF technology. With the increasing awareness
of side effects of ovarian stimulation and better understanding
of ovarian physiology in relation to ovarian follicular
growth and maturation, IVF in natural cycles has gained
great attention and interest for both normal responder and
poor responder patients (4).
1.1. Advantages
Natural IVF cycles are simple, inexpensive and rapid and
side effects associated with ovarian stimulation are eliminated.
Natural cycle offers a more physiological, less drugoriented,
lower risk and more patient-friendly approach
(4). Natural IVF cycles might be more efficient for obtaining
ideal embryos. It can be repeated on a monthly basis, and
the overall chances of success are therefore higher. Some patients
might prefer several successive natural IVF cycles instead
of stimulated IVF cycles, which can only be repeated
once a month (5). It has been reported that the clinical pregnancy
rate with stimulated IVF has reached approximately
25–30% (6). However, repeated stimulated cycles should
span over several months to allow for the ovaries to recover.
Further, if stimulated IVF cycles are repeated, the pregnancy
rate will obviously decrease. |
