Six months and still nothing?

What are the odds on getting pregnant?
In any given month, there is only a 20 to 25 per cent chance that you will conceive, even without any medical issues getting in the way (see below).
On average, most couples will manage to conceive if they try regularly to have unprotected sex over a six month period, but a further 25 per cent will take up to two years to conceive as part of the completely natural process of things.
You are not alone if you have been trying for some time: one in every seven couples will experience some problem in conceiving and worldwide, that's about 80 million couples.

Shouldn't it be easier to get pregnant if you've already had a child?
There are two categories of infertility. Primary infertility occurs when the couple involved have not managed to conceive naturally.
Secondary infertility is when the couple have been through previous pregnancies (that can includes having had children, or an episode of miscarriage) but on this occasion are finding it difficult to conceive naturally.
Interestingly, secondary infertility is far more common than primary infertility.
If you have had a child before, take a look at various factors. Are you trying for a baby with a different partner? Have you had any new and/or problematic medical conditions since you were last pregnant? Bear in mind that you are inevitably older now and that age does have a direct affect on fertility, especially for women. Also, now you have a child or children, your lifestyle may well be very different: stress, tiredness, diet and weight can all play their part in throwing hormones out of synch for you and your partner.

How long should we wait before seeking help?
If you are a young woman (under 30), it is unlikely that your doctor would suggest tests for possible infertility or subfertility (that is, when there is a reduced opportunity for the woman to conceive naturally) until you have been trying for at least 12 months.
If you are over 30, you might want to discuss the issue if you have been trying for every month over more than six months, but your GP is unlikely to feel there is any great cause for concern before 12 months unless she or he feels there are medical or circumstancial reasons to discuss assisted conception any earlier.
If you have had any surgery which might have lead to scar tissue causing a blockage, then you should speak to your GP (or consultant if the treatment is imminent or recent) as soon as you can after deciding to try for a baby. Operations for women including treatment for an ovarian cyst, cancer or appendicitis don't neccessarily cause a problem, but it is worth flagging previous medical issues up so that you can be examined for possible scar tissue growth affecting your fallopian tubes, for example. Operations in men which can affect successful conception may include treatment for a hernia. It is not a given that these events would contribute to an inability to conceive, but it is worth making your health advisors aware of them.

So what do we do now?
If you have been trying for a baby for less than a year then try to relax about the issue and don't make it a problem for yourself mentally or for your relationship with your partner emotionally.
Check out the ThinkBaby articles on Preconception and Conception and Fertillity. These will take you through the processes of charting your ovulation so you have a more accurate idea of when you are at your most fertile, they will also look at issues of health and lifestyle in enhancing your odds on getting pregnant naturally, and give you the lowdown on what you might expect if you have to go for 'assisted conception'.
You could also check out the Human Fertilisation and Embryology Authority website which has a lot of useful information and downloads whether fertility has already become a problem or you just want to understand more about conception. It's not half as daunting or academic as their title suggests!