Women’s Fertility Facts

Age

Age is one of the most important factors to consider as it impacts on female fertility. When a woman is born her ovaries contain around 2 million immature eggs. At puberty when menstruation begins (menarche), a woman has around 400,000 immature eggs remaining in the ovaries. Each month a group of immature follicles grow and one follicle matures and releases an egg. The eggs in the ovaries contain the female DNA that contribute to one half of a successful embryo and pregnancy.

Age is an important factor as increasing age affect the quality of the eggs a woman releases. We start to see a decline in female fertility rates in the mid-thirties and by 37 years age this is more prominent. The rate of decline of female fertility depends on genetic factors but also lifestyle choices.

Body Mass Index

Body mass index (BMI) is often a difficult subject to address within relationships and with a doctor. Many studies have shown that being overweight and obese is bad for the female reproductive system.

An abnormal BMI (>30) has been shown to interfere with menstrual cycles, egg quality, the reliability of ovulation and hormonal regulation. Studies have also shown obesity can disturb the development of the womb lining and affect embryo implantation.

Obese women are three times more likely to suffer unreliable ovulation. The exact mechanisms are not fully understood but excess fat stores seem to affect the brain’s regulatory control over ovulation. Follicular development and reliable ovulation requires a finely balanced hormonal regulation of the ovaries.

Women that are overweight commonly have Polycystic Ovarian Syndrome (PCOS) and they often suffer more severe problems with ovulatory control and irregular periods. Ultimately if ovulation cannot be restored with weight loss and ovulation induction medications such as clomiphene then some women may require and IVF treatment cycle.

An abnormal BMI makes an IVF cycle far less successful, so achieving weight loss is the cornerstone of not only improving the chances of natural conception, but essential before undertaking fertility treatments too. The eligibility criteria for NHS funded IVF treatment cycles requires the woman to have had a BMI <30 for at least six months. T

Smoking

Cigarette smoking has been shown in many studies to be linked to lower fertility rates, worse IVF outcomes and problematic pregnancies. Cigarette smoke contains hundreds of different toxins as well as nicotine that may be harmful to the female reproductive system. There appears to be a dose-dependent effect and it is very individual specific as to whether human fertility is affected.

The reality is that some patients who smoke will still manage to conceive but the effects of smoking are known to be harmful to a woman’s eggs. Smoking is also associated with an increased risk of miscarriage and growth restriction of a fetus. Essentially if you are struggling to conceive or about to embark on fertility treatment you must quit smoking.

Smoking can affect your eligibility for NHS funded fertility treatment, as it requires both partners to be non-smokers for at least six months prior to application. If you are wanting to quit smoking and looking for support you can become Smoke Free.

Alcohol/Caffeine

There have been many studies that have looked at the effects of stimulants such as alcohol and caffeine on fertility. The quality and design of many of these studies has been poor though which explains why there has been mixed findings. Some studies have seen no effect of alcohol on fertility and others suggest it can reduce chances of successful conception.

There is fairly good evidence that high levels of alcohol and caffeine intake during a pregnancy can affect fetal development and increase the risk of pregnancy loss. However, the evidence that alcohol and caffeine significantly affect the chances of conception occurring is questionable.

Diet & Nutrition

The importance of research into the area of nutrition and diet is clear as these are simple things individuals can modify. However, research findings have been fairly inconclusive in many areas due to the design and quality of research studies.

Antioxidants work to reduce oxygen free radical damage to a woman’s eggs. The evidence currently suggests that antioxidant supplementation does not increase the chances of a pregnancy or live birth. There seems to be no disadvantage to taking antioxidants and so their use is not discouraged.

Folic acid and B12 show more promise with regards fertility. There is established evidence with research initially funded by The Wellbeing of Women Charity that folate reduces the chances of neural tube defects in babies. There is also some evidence that increased B12 and folate levels in pre-conception vitamins may increase a woman’s chance of becoming pregnant.

Vitamin D is another important nutritional supplement. Deficiency of this vitamin might be detrimental to fertility but there is no clear evidence that boosting it increases your chance of conception. However, there is well established evidence that Vitamin D can boost your chances of success with an ongoing pregnancy, reducing diabetes in pregnancy and improving baby bone formation.

Fatty acids can be divided into two types. Trans-fats are the artificially created fats that manufacturers tend to use to increase the shelf life and stabilise the flavour of foods. The trans-fats are the bad fats that are more likely to cause weight gain and affect ovulation. The unsaturated fats such as Omega 3, are the long chain fatty acids, and may be beneficial for female fertility.

Dairy food stuffs have long been associated with ovulation related fertility problems. However, the evidence for this is weak at best and there is no strong conclusive evidence supporting this.

Meat, fish and soy is a difficult area to be exact about. Some studies suggest that a higher red meat intake or ingesting meats more likely to be contaminated by environmental pollutants may be bad for female fertility. So eating organically reared meats may help here. Meat alternatives like soy are the main source of phytoestrogens to humans but there has been very little evidence to suggest that this harms female fertility.

In general research into diet and nutrition and fertility has become more prominent in the last 10 years. Sticking to a healthy balanced diet that favours fish, poultry, fruits, wholegrains and vegetables is a good strategy and should optimise your fertility.

Exercise

Excessive exercise and reduced calorie intake will likely have a negative impact on ovulation, menstrual cycles and the womb lining (endometrium). If a woman tends towards a negative energy balance consuming less calories than she uses up exercising, then this affects the hypothalamus and its control over ovulation.

Female athletes who have an increased frequency, intensity and duration of exercise are more likely to see a decrease in fertility. It has also been shown in some research that women doing high intensity cardiovascular exercise for more than 4 hours a week we on average more likely to experience fertility difficulties and were less successful with IVF.

However, if obese women tended towards a negative energy balance and lose weight as a result of exercising regularly this can have a positive effect on ovulation. So the impact of exercise is very individual and depends on a woman’s body mass index and normal physiology.

Some women will see a minimal effect from high intensity exercise, but if you are struggling to conceive or have menstrual irregularities and a very low body weight think carefully about whether your exercise routines are affecting your fertility. It is always best to speak with a gynaecology and fertility specialist about your exercise levels if you are unsure, but especially if you are not having regular menstrual cycles.

Infections

Infections of the female reproductive tract can damage your fertility. There are far too many different types of infections that can affect the female genital tract to cover each one in detail here. However, there are a few important infections you should consider if you have ever had unprotected intercourse in your lifetime.

Chlamydia is the most common sexually transmitted infection and it can damages a woman’s fallopian tubes affecting her fertility. Chlamydia is often silent without symptoms, though some women will experience mild spotting in their menstrual cycle. The infection causes inflammation in the reproductive tract and scarring and blockage of the fallopian tubes and can cause in extremis severe pelvic inflammatory disease (PID). Around 1 in 5 women who have fertility problems have blocked fallopian tubes and chlamydia is responsible in a large proportion of these cases for the problems that occur.

It is important to screen for sexually transmitted infections between relationships to ensure you are not put at risk by having unprotected intercourse with a new partner. Old chlamydia infections are often found during infertility investigations, but by this stage often the damage to the fallopian tubes has already occurred.