The short answer is no — there's not much the average couple can do to affect a baby's sex.

While old wives' tales suggest that a woman's diet or sexual position during conception can affect a baby's sex, these theories remain unproved. Likewise, researchers have found that timing sex in relation to ovulation — such as having sex days before ovulation to conceive a boy or closer to ovulation to conceive a girl — doesn't work.

Rarely, couples face the agonizing problem of knowing they could pass a genetic trait to a child of a specific sex — usually a boy. Under those special circumstances couples might use high-tech interventions to influence the chance of conceiving a girl. For example:

• Preimplantation genetic screening. With this technique — which is used in combination with in vitro fertilization — embryos are tested for specific genetic conditions and sex before they're placed in a woman's uterus.
• Sperm sorting. Various sperm-sorting techniques — which require artificial insemination or in vitro fertilization — can be used to reduce the likelihood of passing on a genetic condition, as well as select a child's sex.

These procedures are not recommended for choosing a baby's sex for nonmedical reasons. If you have concerns about passing on a genetic condition to your baby, talk to your health care provider.