Lots of us are waiting until our 30s to conceive, when our fertility is dropping. Some things take time, so be patient and don't jump into infertility therapy, warns the March 7th issue of the New England Journal of Medicine. The use of assisted reproductive technologies is associated with a significant increase in the risk of major birth defects and in the likelihood of having a low-birth-weight infant.

Dr Jennifer J Kurinczuk, from the University of Leicester, England, looked into the rate of major birth defects among 301 infants conceived with intracytoplasmic sperm injection, 837 infants conceived with in-vitro fertilisation, and 4,000 infants conceived naturally. The rate of major defects in the first two groups was twice that of the naturally conceived children. In addition, infants conceived with an assisted reproductive technology were more likely to demonstrate multiple major defects, chromosomal defects and musculoskeletal defects.

Low birth weight is another risk, as babies conceived by assisted reproductive technologies are two-and-a-half times more likely to be of low birth weight than infants in the general population, according to a study by Dr Laura A Schieve at the Centers for Disease Control and Prevention in Atlanta.

If you are pregnant with the help of reproductive technology, don't panic.

Dr Allen A Mitchell from the Boston University School of Public Health says that while use of assisted reproductive technologies appears to double the risk of birth defects or low-birth-weight infants, the absolute risks are still relatively low.

Still, he suggests, the current findings should give pause to couples who proceed with infertility therapy before attempting to conceive naturally for at least 12 months.