Grieving the fact that your baby isn't going to be the sex you hoped for, whether for 'family balance' or how you imagined parenting them, is termed gender disappointment and, according to Melbourne consultant psychologist Dr Di McGreal, it can be as tough to deal with as other types of reproductive loss.

There are many parents who are often sad and disappointed if the sex of their child is not what they wanted. Although these emotions tend to disappear, parents can then have feelings of guilt and fear that they won't bond with the baby.

"There can be quite a deep grief associated with that," McGreal says. "It's typically after a 20-week scan, when a couple were hoping for a particular sex, and discover [what] they are having."

"For most people these feelings of disappointment only last during the pregnancy," says McGreal . "As soon as the baby is placed in their arms, they make eye contact and fall in love. Thankfully nature works in that way."

This was certainly the experience for Bron Mills of Raymond Terrace, NSW, who was shocked to discover at the 20-week scan that she actually very much did want a girl, after having three boys, Josh, 13, Dom, 7, and Charlie, 3.

"I was convinced that I didn't mind either way, but I did think that I was having a girl, as I had morning sickness for the first time, so I was a little nervous," said Mills. When the sonographer told her and husband Adrian, that they were having a little boy, she spent the rest of the scan holding back tears. "I looked over to Adrian who gave me the loveliest smile that it was okay," says Mills.

But when the couple got home, Bron lay down on her bed and stayed there for hours, crying. "I couldn't talk. I couldn't leave my bed without a bout of tears starting again. I couldn't even answer text messages without tears. The three boys were just gleaming at having a baby brother. They were over the moon. I didn't realise that I wanted to hear those words, 'she's a girl', but obviously a small part of me did."

If you've had a scan and you are disappointed by the sex of your baby, McGreal says it's important to know that you are not grieving the baby you are carrying, but the fantasy you have created around having either a boy or a girl.

Couples picture themselves parenting a little boy or girl, or they may have three girls and are desperately hoping for a boy. When their dreams aren't realised, they can be devastated.

One of the best ways to overcome the sadness is to write a letter expressing your feelings. You could write to the baby you thought you would have or you could write to your unborn baby, saying you're upset, but also how much you want to meet him. Once you've written the letter, burn it, McGreal says.

"Do whatever you need to do to let it go. Then start to enjoy the fact that you are going to have this beautiful baby in your arms," she says, "because it's not that baby, it's the fantasy you created about the other-sex baby, that is really causing you distress."

"If you find that you are still upset once your baby is here, it's time to seek help. It's rare for people to struggle beyond the birth and if they do they certainly need to get some counselling," McGreal says.

In Australia, it's not possible to select your baby's gender with certainty as IVF clinics are not allowed to do it on moral grounds. And it's hard to dictate what sex the baby will be at conception, says Melbourne specialist obstetrician Dr Kate Duncan, despite theories about timing the intercourse to favour boys or girls, or changing your diet.

If you want a boy baby, you're advised to have intercourse shortly after ovulation, and a girl just before. "Trying to influence gender at conception is difficult and none of the methods suggested in books can reasonably claim better than 70 percent one way," says Dr Duncan. This compares with a 50 percent chance of having a boy or a girl anyway.

So why does it seem that many families seem to have a run on the same gender of children? There is nothing they did or didn't do, the sex of the child would depend on the proportion of X and Y chromosomes in the male's output of sperm.