Sperm Survival

Soon after intercourse, the vaginal secretions return to their more typical acid state and sperm can only survive for six hours. The survival of sperm in cervical mucus, and the uterine and tubal fluid is the subject of debate. It probably varies between individuals. Originally it was thought that the maximum survival was four days but it is now believed that on occasion it may be up to 7 days.

Whereas a woman releases one egg each month, each adult testicle produces 1,000 sperm each second. Libido in women seems to peak around the time of ovulation (egg release). The secretion of the vagina is increased before intercourse when it becomes more alkaline than at other times. This more alkaline environment is more favourable to sperm survival. The ballooning of the upper vagina before intercourse reduces loss of seminal fluid after intercourse. There is evidence that during orgasm the uterus exerts a negative pressure, which tends to suck sperm in from the vagina. 

Egg Survival

From knowledge gained from IVF, we know that ova (eggs) are most likely to be fertilised within the first 24 hours after ovulation. However, when the embryologist finds no evidence of fertilisation after 24 hours, re-insemination with fresh sperm may result in fertilisation. This would suggest that insemination, whether spontaneous or artificial is most likely to result in pregnancy if it occurs before or within twenty-four hours of ovulation.

Fertile Phase

Ovulation occurs 14 days before your next period is due. If your periods are occurring regularly every 28 days, your fertile phase will be from day 7 to day 15. If the cycle is irregular, you have to allow for your shortest and longest cycles. If, for example, a woman has a cycle varying from 21 to 35 days, then the potential fertile phase could be somewhere between day 1 and day 22; this is assuming that the current cycle could not be longer than 35 days although in reality one cannot be certain.

Unlike the vast majority of other species, we humans do not have breeding seasons. An interesting observation once quoted by an expert at The Royal College of Obstetricians and Gynaecologists related to the monthly cycle. The best suggestion he could find was that in primitive ages, fertility would be enhanced if the woman released her monthly egg at a time when there was no moonlight for her man to go out hunting for food! Whereas in other species, such as the rabbit, coitus induces ovulation there is no evidence that this occurs in humans.

The cervical mucus (the fluid in the neck of the womb) becomes more fluid and stretchy under the influence of the unopposed oestrogen before ovulation. It is only around the time of ovulation that the cervical mucus permits sperm through at other times it is hostile.

The Ideal birth control

The perfect contraceptive would be:- 

Pearl Index

The Pearl pregnancy rate is the standard method for comparison of effectiveness. This measures the number of pregnancies that occur for each contraceptive method if used by 100 women for one year. Long-term users of a method probably have lower pregnancy rates than indicated by thePearl rate because those who have failures are likely to change method. Furthermore failures are more likely in younger women who may be more fertile and more sexually active. This explains why there is a range of quoted Pearl rates for each contraceptive method.

Table 13.1 Pearl Index - Pregnancy rates per 100 couples in first year of use.

Rhythm Method

As sperm can survive for seven days, there are probably no 'safe' days between cessation of the period and ovulation (Q13.4). Fertility awareness (e.g. rhythm methods) has one of the highest failure rates of contraceptive methods (Pearl Index)but there are no side-effects and the method is acceptable to some cultures more than others. If ovulation can be predicted accurately, intercourse from two days onwards would theoretically be unlikely to result in conception. Ovulation occurs 14 days before the next period. Calculation of the post ovulation 'safe' period is easier for those women with a regular cycle. Ultrasound has shown that ovulation pain (Mittelschmerz) tends to begin 24 48 hours before ovulation.

The basal temperature can be used as a guide to the timing of ovulation. Following ovulation, progesterone is produced (Fig 2. 3)

And this results in the temperature rising by 0.5 degree centigrade. The temperature should be basal rather than after activity and is generally measured in the morning on waking. If you record your temperature for a couple of months and feel confident that your chart shows clear changes this method may have advantages if you are reluctant to use other methods. From the medical point of view this method is not regarded as being effective.

Assessment of the cervical mucus provides an indication of ovulation but it is not reliable. Progesterone, which is released into the circulation after egg release and though the second half of your menstrual cycle, makes the mucus less profuse and more sticky.

The rhythm or calendar method involves calculation of the shortest and longest cycles over the last twelve cycles. The fertile phase is calculated as 20 days subtracted from the shortest cycle and 11 days from the longest cycle. If the cycle is regularly 28 days the fertile phase would be from Day 8 (28-20) until Day 17 (28-11). If the cycle varies from 21 to 35 days, the fertile phase would be from Day 1 to Day 24. For those with irregular cycles there may be few safe days.

Related Medical Abstracts - Click on the paper title:-

birth control and

Breast Feeding

If your baby is less than six months old, you are fully breast feeding, and your periods have not recommenced, the chance of pregnancy is in the order of 2%. Beyond six months, the protective effect of breast-feeding diminishes.

Coitus Interuptus

Withdrawal of the penis before ejaculation was historically the only method of birth control. There are no dangerous side-effects but reported failure rates of 10/100 women years indicate that it has only limited effectiveness (Table13.1).Furthermore, lack of satisfaction for some partners and anxiety that withdrawal may be too late are additional problems. In one study, 31 % of women discontinued the method because they found it unpleasant but this compared to 54% who found the sheath unpleasant. Although coitus interruptus is not promoted by family planning doctors, there are times when a couple have no other method available; it is certainly more effective than no method at all.

Barrier Methods of birth control

Sheaths

Condoms made from animal skins, bladders or bowel have been in use for many centuries but probably more for the prevention of infection than pregnancy. Rubber condoms first became available in the middle of the nineteenth century. In the UK, about 20% of couples use condoms. In Japan, where the pill only became available in late 1999, 75% of couples use condoms. Recognition of the dangers of sexually transmitted diseases, and HIV in particular, have provided an additional benefit for condom use.

With motivation and correct use, failure rates of just one pregnancy per 100 woman years have been reported although the average for careful users is about 4 pregnancies per 100 woman years. The addition of vaginal spermicides probably reduces the failure rate.

The condom is likely to fail if not used correctly. If there is genital contact before the condom is applied there could be some sperm around the penis from previous intercourse. Withdrawal should occur before the penis becomes flaccid and care be taken to ensure that there is no spillage of semen. Sharp fingernails can damage the sheath during application. Several local treatments for vaginal infections, hormone preparations applied within the vagina, baby oil, sun tan preparations and vaseline can weaken the sheath. It is probably best not to rely on condoms if there has been any recent vaginal treatment. The lubricating KY jelly does not damage condoms.

The advantages and disadvantages of sheaths are summarised in Table 13.2.

Table 13. 2 Advantages and disadvantages of condoms (sheaths) as a method of birth control.

Advantages	Disadvantages
Easily obtained.	Interruption of foreplay.
Cheap (free on NHS).	Reduced sensitivity for male partner.
Very effective.	Great care required.
Protects against sexually transmitted disease.	Occasional allergy for either partner.
Possibly reduce risk of cervical cancer.	Vaginal treatments may damage sheaths (Q13.10)

Vaginal Birth Control

There is reference to the use of vaginal contraception going back more than 3,000 years. Nowadays there are vaginal diaphragms that fit over the cervix and front of the vagina and cervical caps that fit over the cervix only. Until the development of the pill, the diaphragm was very popular with about 10% of couples relying on it.

Diaphragm

These can be obtained either from your local general practitioner or a family planning clinic. The correct size of diaphragm is determined by a doctor trained in family planning. The caps are measured across the external diameter and there is a range from 50 to 100 mm in 5mm steps. The doctor will check at a follow up visit that you have learned to introduce the diaphragm correctly.

During intercourse the vagina enlarges so that unlike male or female sheaths the diaphragm cannot provide a complete barrier to sperm. The objective of the diaphragm is to retain spermicide in the area of the cervix and prevent motile sperm from entering the cervical mucus. The cervical cap should stay attached to the cervix by suction and it is a more effective barrier method than the diaphragm. The diaphragm should remain in place for at least six hours after intercourse and it is then removed and washed in soapy water.

It is wise to check the diaphragm from time to time to ensure that there is no damage. It should be held up to the light to see that there are no holes and the outer ring should quickly return to its round shape after squeezing. A diaphragm will usually last for about two years. If it is lost, a replacement of the correct size can be purchased at a chemist.

Pregnancy rates vary between 2-15 per 100 women years (Pearl Index).

The advantages and disadvantages of vaginal methods of birth control are summarised in Table 13.3.

Table 13. 3

Advantages and Disadvantages of Vaginal Methods of birth control

Contraceptive Sponge

These are small polyurethane sponges, shaped to fit over the cervix. They are disposable, impregnated with spermicide and they have a tape allowing them to be removed easily. The sponge is moistened before insertion. A sponge is introduced up to 24 hours before intercourse.

Pregnancy rates up to 25 per 100 women years have been quoted.

Female Condom

The latest female condom, Femidom, is made from polyurethane and has a lubricant. There is an inner ring measuring 60 mm diameter and an outer ring of 70mm. The rings are squeezed to allow insertion.

They can be purchased without need for medical advice or prescription. The female partner takes responsibility and there is less loss of sensation for the male partner than with the male condom. It provides effective protection against sexually transmitted disease. This method of birth control became available in 1992. There are very few studies to determine its acceptability or effectiveness.

Spermicides

Spermicides (chemicals that kill sperm) have been available for many generations. The most popular spermicide currently available is nonoxynol-9. Spermicides are not as effective in real life as they appear to be in the laboratory.

Female Condom pregnancy rates

Pregnancy rates of up to 30 per 100 woman years have been reported (Table13.1). In view of these potentially high failure rates, family planning doctors generally recommend that you should use spermicides only in combination with other methods.

On balance it would seem that spermicides are likely to reduce your risk of pre-malignant and malignant conditions of the cervix.

Spermicides have been found to provide some protection against a variety of sexually transmitted diseases. From a medical point of view, additional precautions with a barrier are to be recommended.

Most chemicals introduced into the vagina are absorbed to some extent and this is true for spermicides.

There have been reports of possible harmful effects on the liver but these remain unproven.

There are probably no harmful effects on the fetus if you have been using spermicides in early pregnancy.

What is Depo-Provera?

This is an injection of the progestogen medroxyprogesterone acetate, which lasts for twelve weeks and can then be repeated. The first injection is usually given in the first four days of a period, or within seven days of a miscarriage or pregnancy termination. After childbirth, Depo-Provera is best delayed for five or six weeks as it could otherwise cause troublesome bleeding.

What are the advantages of Depo-Provera?

Depo-Provera provides a highly effective and convenient method of contraception. The failure rate is low (0.5 in 100 woman-years) and is equivalent to the combined oral contraceptive pill. Some women find that their periods are less heavy and less painful. Premenstrual tension may improve.

Depo-Provera does not increase blood pressure.

There is no need to discontinue Depo-Provera before surgery.

What are the disadvantages of Depo-Provera?

In common with other progestogen only contraception, there may be irregular bleeding.

How soon will my fertility return after my last Depo-provera Injection

It can take up to a year for fertility to be restored following Depo-Provera and this should be kept in mind when planning a pregnancy. This does not mean that you can take a chance after three months: if you do not want a baby, contraception will be required. 

Teen Contraception

Contraception for adolescents has been discussed in (Q5.19).

Contraception over 40

From the age of 40 years, fertility decreasesQuickly (Pearl Index). It is wise for birth control to continue for two years after your last spontaneous period if you are more than 45 and for one year if you are more than fifty. For women who seem to have an earlier menopause, there is a tiny risk of ovulation and they should use birth control if they wish to be certain. For a non-smoker, who is not obese and who has a normal blood pressure, the combined oral contraceptive pill can be continued until the menopause. If the combined pill is contraindicated a progestogen only pill provides a good alternative.

The IUCD, barrier methods and sterilisation have a place. If periods are heavy the LNG-IUS (Mirena) may improve the loss and provides excellent birth control.

Menopause

A blood test, taken on the last day of the pill free interval, for FSH and oestradiol levels provides a valuable indication on whether you have reached your menopause (Q 26.14). If you are taking cyclical HRT, you should complete your current pack and then withhold the HRT for at least 7 days before having the blood test. Some would suggest that the tests should be repeated two months later.

Persona

The Persona is a small computerised monitor that assesses your early morning urine samples for levels of two hormones LH and an oestrogen. Sixteen daily tests are usually required in the first cycle and eight after that. A red indicator indicates fertile days. First year failure rates are in the order of 6 per hundred women-years (Table13.1). One authority suggests that if sheaths are used from Day 1 until the first 'red' day, abstention through the red days and unprotected intercourse from the second 'green' day, failure rates of less than 3% could be expected.

Persona is 94% effective - if one hundred women use it and no other method then 6 would be likely to conceive in one year.

Support Groups

Members of a support group, provide each other with various types of help and information for a particular shared difficulty.

The support may take the form of providing relevant information,

• relating personal experiences,
• listening to others' experiences,
• providing sympathetic understanding and
• establishing social networks.

A support group may also provide ancillary support, such as serving as a voice for the public or engaging in advocacy.

Support groups maintain interpersonal contact among their members in a variety of ways.

Support groups also maintain contact through printed information rich newsletters, telephone chains, internet forums, and mailing lists.

Support groups offer companionship and information for people coping with diseases or disabilities. Support groups may not be appropriate for everyone, and some find that a support group actually adds to their stress rather than relieving it.

Evaluation of the quality of Web sites is discussed in (internet information). You may find that several general women's health sites may help you (internet information).

The following are more specialised relevant Web sites:-

This page was last updated 1st April 2008