Physiology of the female reproductive system
The female reproductive system consists of the external and the internal genitalia. The external genital organs are visible outside the body and begin to mature when a girl reaches puberty. The internal genitalia are the organs where fertilisation and conception takes place. The uterus, fallopian tubes, ovaries and the vagina are the main structures of the female reproductive system. The organs of sexual reproduction are the gonads, which are the ovaries in females and the testes in males. Females produce female gametes or eggs (males produce male gametes or sperms). Sexual reproduction is the fertilization of a female gamete by a male gamete.
When a female is born, each of her ovaries has hundreds of thousands of eggs, but they remain dormant until her first menstrual cycle, which occurs during puberty. At this time, during adolescence, the pituitary gland secretes hormones that stimulate the ovaries to produce female sex hormones, including oestrogen, which helps the female develop into a sexually mature woman. Also, at this time, females begin releasing eggs as part of a monthly period called the menstrual cycle. Approximately once a month, during ovulation, an ovary discharges a tiny egg that reaches the uterus through one of the fallopian tubes. Unless fertilised by a sperm while in the fallopian tube, the egg dries up and is expelled from the uterus. If a female and male have sexual intercourse within four days of ovulation, fertilisation can occur. When the male ejaculates semen is deposited into the vagina. Between 200 and 300 million sperm are in this small amount of semen, and they 'swim' up from the vagina through the cervix and uterus to meet the egg in the fallopian tube. Only one sperm is required to fertilise the egg.
What is the menstrual cycle?
The menstrual cycle is the way a woman's body gets ready for the possibility of pregnancy each month. A cycle is counted from the first day of one period (menstruation) to the first day of the next. An average cycle is 28 days, but anywhere from 23 to 35 days is normal. The day that bleeding starts is counted as the first day of a given cycle. The menstrual cycle is controlled by hormones released by the hypothalamus the pituitary gland and the ovaries. The menstrual cycle has four stages:
- The menstrual phase
When a women is having her period it means that the lining of the uterus is breaking down and slowly flowing out of her body through the vagina over a period of days called the menstrual phase. Menstruation is the term given to the periodic discharge of blood, tissue, fluid and mucus from the reproductive organs of sexually mature females. The flow usually lasts from 3 - 6 days each month and is caused by a sudden reduction in the hormones, estrogen and progesterone. For most of a woman's life, the egg that is released approximately once each month will not become fertilised, so the lining that develops each month for the possibility of a fertilised egg cell won't be needed. Over a period of days the blood vessels shrink and the uterus will shed the unneeded lining, made up of a small amount of blood and tissue.
- The preovulatory phase
The preovulatory phase (before the egg cell is released) is next and starts as soon as the menstrual phase (the period) has ended. During the preovulatory phase the uterine lining thickens with an increased numbers of blood vessels. The lining of the uterus needs to prepare itself for the possibility of supporting a fertilised egg. An egg is also ripening in one of the ovaries in preparation for ovulation.
- The ovulation phase
The third phase is the ovulation phase at midcycle, which in a 28-day cycle would be day 14. A mature egg is released from one of the ovaries during ovulation. Some women may have some slight discomfort during ovulation usually described as a twinge or cramp in the lower abdomen or back. Many women have no sensation that they are ovulating. Once released the egg travels into the fallopian tube and then begins a four to five day journey to the uterus. The egg lives twelve to twenty-four hours in the fallopian tube after it has been released from the ovaries and then disintegrates if not fertilised. Sperms can survive for up to five days inside a woman's reproductive system. The few days before, during and after ovulation are a woman's "fertile period" - the time when she can become pregnant. Because the lengths of menstrual cycles vary, many women ovulate earlier or later than day 14 of the cycle. Stress and other things can sometimes cause a cycle to be shorter or longer. This event occurs approximately once a month near the midpoint of a woman's menstrual cycle.
- The postovulatory phase
Most months the egg cell simply dies in the postovulatory phase (after the egg cell is released), the endometrium continues to develop and the uterine glands secrete nutrient materials. If the egg cell meets a sperm cell and is fertilised by a sperm it attaches to the uterus. Fertilisation usually occurs when the egg is in the fallopian tube. If a woman becomes pregnant her menstrual cycle will stop during the time that she is pregnant. If conception doesn't occur, the hormone levels drop. Below a certain level of hormones, the uterine lining can no longer be maintained and the lining of the uterus breaks down, menstruation begins, and the cycle repeats.
How to know your fertile period?
A woman is most fertile during mid cycle. Ovulation generally occurs 14 days before the start of the next period. To successfully conceive, it is best to have intercourse in the fertile window of opportunity starting at about 2-3 days before ovulation. Usually, the fertile period in a woman, with a 28 days cycle, extends from day 11 to day 18. It is important to keep a track of your periods. Mark the calendar on the day you get your period. This is Day One. Count each day until your next period arrives. You may need to do this for three or four months to get an accurate measure of the length and regularity of your cycle.
- If your cycles are very regular, you may be able to determine when you ovulate: in the average menstrual cycle, ovulation occurs 14 days before the menstrual period arrives - or on day 14 of a 28-day cycle. So if you subtract 14 days from the length of your cycle, you'll get an idea of when you ovulate.
Use the Ovulation calculator in the pregnancy section to determine the most likely date of your ovulation.
- If your cycles are not very regular, or you'd like a more accurate picture of your ovulation then:
1. Track your temperature: One of the indications that ovulation has occurred is that a woman's basal body temperature increases slightly during ovulation. You can detect this 'thermal shift' by taking your temperature every morning at the same time before you get out of bed. If you chart your temperature each day for a few months, you'll begin to see a pattern that will help you predict when you are about to ovulate. Most women's temperature increases about a half a degree 24 to 48 hours after ovulation.
2. Watch for changes in your cervical mucus: This method does not exactly pinpoint but gives you some indication of whether you're in a fertile period or not. As your body prepares to ovulate, it produces larger quantities of thin, clear cervical mucus, a substance that smoothes the way for the sperm to meet the egg. On your most fertile days, just before ovulation, the mucus will appear clear, stretchy, and slippery. After ovulation, when your fertile days are past, the mucus usually becomes thicker and then gradually dries up.
Tips to help a woman conceive
Being healthy and having regular menstrual cycles increases the chances of conceiving a healthy baby and carrying the baby to full term.
Basic health tips include:
- Don't smoke
- Avoid alcohol
- Reduce coffee consumption
- Eat a healthy and nourishing diet
- Manage stress levels
- Exercise regularly
If you're under 35 and have had regular intercourse for 12 months, or 35 or older and have been trying for six months, then it's time to see the doctor for a fertility evaluation.
When you come off the pill
If you have just come off the contraceptive pill and are ready to have a baby, be prepared for the fact that conception may not happen straight away. The hormones in the pill have been running and regulating your menstrual cycle, not your body. When you come off the pill it takes a little while for your body to regain its natural hormonal rhythm, which varies from one woman to another.