Related Experiment Video
Updated: Jun 15, 2026

The Immediate Partial Removal of Cumulus-Oocyte Complexes: A Refined Approach for Rapid Observation of In Vitro Fertilization
Published on: October 18, 2024
[Natural cycle versus ovulation induction cycle in intrauterine insemination]
1Department of Gynecology and Obstetrics, Nanjing University School of Medicine/Nanjing General Hospital of Nanjing Military Region, Nanjing, Jiangsu 210002, China.
Objective:
To compare the results of the natural cycle and ovulation induction cycle in intrauterine insemination (IUI) for infertile couples of different ages.
Methods:
We retrospectively analyzed 746 IUI cycles for 363 infertile couples, who were divided into a natural cycle (NC) and an ovulation induction cycle (OIC) group. The two groups were respectively subdivided into a < 35 yr and a > or = 35 yr age group, and, according to the drugs used, the OIC group was again divided into subgroups of clomiphene citrate + Progynova (CC + P), menopausal gonadotropin (HMG) and CC + HMG. The rates of clinical pregnancy, abortion and delivery were compared among different groups.
Results:
The pregnancy rate was significantly lower in the NC than in the OIC group (11.35% versus 19.61%, P < 0.01), but the rates of abortion and delivery had no significant differences between the two groups (P > 0.05), nor did the rate of clinical pregnancy among the subgroups of CC + P, HMG and CC + HMG (18.00%, 25.00% and 19.35%, P > 0.05). The < 35-year-old patients showed statistically lower rates of pregnancy and delivery in the NC than in the OIC group (P < 0.01 and P < 0.05), while the > or = 35-year-olds exhibited no significant differences in the rates of clinical pregnancy, abortion and delivery between the two groups.
Conclusion:
The ovulation induction cycle could achieve a higher pregnancy rate than the natural cycle in IUI, whether with CC + P, HMG or CC + HMG, particularly for the infertile patients under 35 years. But the natural cycle is preferable for the > or = 35-year-olds.
Related Concept Videos
Ovarian Cycle
In Vitro Fertilization
The IVF process begins with ovarian stimulation, during which reproductive endocrinologists prescribe hormonal medications to stimulate the ovaries to produce multiple eggs instead of the single...
Intrauterine Drug Delivery Systems
Hormonal Control of the Ovarian Cycle
Before puberty, the hypothalamus releases GnRH in a low frequency, low amplitude pulsatile manner. This along with the immature hypothalamic-pituitary-gonadal axis activity, results in low estrogen levels and the absence of a fully functional ovarian cycle. At puberty, GnRH secretion increases in both frequency and...
The Menstrual Cycle
The menstrual phase occurs from days 1 to 5 and involves the shedding of the stratum functionalis, as a uterine...
Hormonal Regulation of the Menstrual Cycle
At puberty, GnRH begins a pulsatile release pattern, which triggers the anterior pituitary gland to secrete follicle-stimulating hormone (FSH) and luteinizing hormone (LH). The frequency and amplitude of GnRH pulses vary across the menstrual cycle, with faster pulses favoring LH release and slower pulses favoring FSH release.

