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Natural Conception

What happens normally – Menstrual Cycle

The first day of the cycle coincides with the first day of menstruation (red blood before 2:00 PM). In the hypothalamus of the brain, the secretion of FSH (follicle-stimulating hormone) has already begun, which acts on the ovaries, promoting the maturation of about 1000 follicles per month (each follicle contains only one egg). Eventually, one follicle will mature – the dominant follicle – and will lead to ovulation (while the rest are destroyed) around the 14th day of the cycle. With the release of the egg, the empty follicle, the corpus luteum, begins to produce progesterone to prepare the endometrium for possible implantation. During these days, the so-called implantation window opens, and the endometrium becomes receptive to the embryo in case of conception.

When is my ovulation?

The average duration of the cycle is 28 days, but it can vary between 21 and 35 days. The first half of the cycle before ovulation is called the follicular phase of the cycle, and its duration varies from cycle to cycle and from woman to woman, while the second half after ovulation is called the luteal phase and always lasts 14 days. Because most women have a 28-day cycle, it is commonly believed that ovulation occurs on the 14th day (28-14=14). This is incorrect because if you have a 35-day cycle, ovulation occurs on the 21st day (35-14=21), and if you have a 21-day cycle, ovulation happens as early as the 7th day (21-14=7)!

What is menstruation?

In the second half of the cycle (in the luteal phase), the endometrium, the inner lining of the uterus, which has thickened and filled with glands to receive the fertilized egg, is shed if no conception occurs. The signal for menstruation is given by the abrupt decrease in female hormones. Therefore, menstruation clears the body of the remnants of the dissolved endometrium, which are useless in the absence of pregnancy, and prepares the organism for a new cycle.

What are my fertile days?

Human reproduction results from the union of sperm with the egg. The egg lives for only 24 hours. If sexual intercourse occurs on fertile days, sperm can survive in the vagina for about 3 days. Therefore, although there is technically only one fertile day, due to the long lifespan of sperm and the relative instability of ovulation, around 6-7 days around ovulation are considered fertile and risky.


Sperm travel through the vagina, cervix, and uterus to reach the fallopian tubes. The fallopian tube, with the help of its cilia, captures the freshly released egg after ovulation. In the fallopian tube, fertilization of the egg by a single sperm occurs. The fertilized egg (zygote) remains in the fallopian tube for the next 3-4 days, dividing into 2, 4, 8, 16 cells as the tube guides it towards the uterine cavity. This highlights the significant nutritional role of the fallopian tubes, which unfortunately cannot be detected by falloposcopy, as it only shows whether the tubes are open or not (a hydraulic role) and not their functional integrity.


Then, on the 5th day, in the form of a blastocyst (composed of about 60-120 cells), the embryo migrates to the uterine cavity, embeds itself in the endometrium (“conception”), and continues its development. Implantation is the most complex process, requiring the cooperation of dozens of hormonal, biochemical, immunological, and paracrine factors.

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