2 June 2016

How does Ovulation work?

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Trying for a baby brings many questions to mind, about human biology and the reproductive cycle – topics we may only have touched on in science class at school. One such question is how ovulation and the process of conception work - exactly.

The first step for any woman planning to get pregnant is to understand the timing of the menstrual cycle. The time from the start of your period to ovulation (when hormones in your body trigger the release of an egg) varies from woman to woman. On average ovulation occurs about 8-14 days after the day of your first period starts. However, it can range between 8 and 18 days depending on the length of your cycle.

At ovulation, an egg is released from the ovaries. It is picked up by and travels down one of the fallopian tubes towards the uterus where, if intercourse has taken place within the last four days, it may meet sperm.

Eggs live and can be fertilised for 12-24 hours after being released. Sperm can live and stay active in your body for between 48 hours and 5 days.

Hormones control the events leading up to and beyond ovulation. The pituitary gland produces two critical hormones:

• Follicle stimulating hormone (FSH)
• Luteinising hormone (LH)

Hormones also prompt an increase in blood supply to the womb in preparation for implantation. It takes up to five days for the fertilised egg to reach the womb and embed itself in the lining.

If the egg is not fertilised, or if the fertilised egg cannot attach to the womb lining, then a period begins.

The male sperm
At the point of ejaculation during intercourse, a man can release up to 300 million sperm into his partner’s vagina. The sperm must travel through the cervical mucus into the uterus and then into one of the two fallopian tubes before they can meet with an egg.

Only a small proportion of those make it through the neck of the uterus and on to the fallopian tubes. The sperm must be actively moving, of normal appearance and of sufficient quantities to be considered normal. It must also be capable of moving through the fallopian tube, where the egg is fertilised

Sperm can survive in the cervical mucus for 5 days around the time leading to ovulation.
Finally, fertilisation of the egg occurs if one sperm that is capable of penetrating the outer layer of the egg makes a successful journey.

The moment of conception
At the moment that the sperm penetrates the egg, a reaction is triggered that makes the egg resistant to all other sperm. Once the sperm penetrates the egg; the chromosomes carried by the sperm and the egg combine and the egg is fertilised.

Within hours, the fertilised egg now known as an embryo develops in the fallopian tubes for the first three days. Then it travels back down the tubes into the uterus. By day five, the embryo becomes a blastocyst and once it hatches or breaks free from its shell, embeds itself in the lining of the womb and the female becomes pregnant.

Once embedded, the embryo secrets chorionic gonadotropin (hCG) a hormone that encourages the production of progesterone. Hoe pregnancy kits detect hCG and can therefore confirm if a woman becomes pregnant.

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