If you're a taller-than-average woman in the US, you're more likely to experience multiple-birth pregnancies than women of average height.

So concludes a study from the Journal of Reproductive Medicine published in September of 2006. The study, conducted by Gary Steinman, MD, PhD, of the Long Island Jewish (LIJ) Medical Center, found that the reason for the increased risk could be traced to Insulin-like growth factor (IGF), which influences both height and multiple births.

A protien the liver releases in conjunction with growth hormones, Insulin-like growth factor (IGF), ups the sensitivity of ovaries to hormones that stiumulate follicles and increase the rate of multiple pregnancies.

Dr. Steinman examined records of 129 women who bore identical or fraternal twins or triplets (105 sets of twins, 24 sets of triplets) comparing them to records of US women of average height, sourcing the National Center for Health Statistics. Multiple-birth mothers averaged 5'5", compared to the average US woman's height of 5'3".

IGF also has been found to prompt cells in long bone shafts to grow. Other studies have found that people of lower-average height have lower levels of IGF. Additionally, IGF studies have concluded that elevated levels of IGF might assist in embryo survival during early gestation.

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