How likely are you to have multiples?

multiples__1458740768_162.206.228.38When you’re contemplating having a baby and trying to conceive, most of us imagine just one baby at a time.  The thought of multiples may have crossed your mind but how likely are you to have multiples? Today we’re exploring that very topic.

Types of Multiples and Statistics

There are two types of multiple births that can occur:  identical and fraternal.  Identical multiples develop when an egg splits into two or more eggs and is fertilized by the same sperm.  Identical multiples will therefore look very similar and always be the same sex.  Fraternal multiples happen when more than one egg drops during ovulation and the eggs are fertilized by separate sperm.

Twins occur in around 3 out of every 100 births in the U.S. Identical twins occur in approximately 3.5 of every 1,000 births.  Triplets and beyond develop in about 1 out of 837 births.

Factors that Affect Likelihood of Multiples

Having identical twins, triplets or more is somewhat a fluke of nature.  There is not a known cause of an egg splitting into multiple eggs.  However, women who have identical multiples in their family have a slightly higher risk of giving birth to identical twins.  This is especially true if she herself, her siblings, her mother or her sister’s children are identical multiples.

On the other hand, more factors affect your likelihood of having fraternal multiples.  First, these factors are all based on the mother’s history, genetics, and lifestyle.  Since multiples are a result of a mother’s ovulation, a father’s sperm does not come into play.

Here’s what the statistics show:

  • Women in their 30s and 40s are more likely to have multiples than those in their teens and 20s.  As we age, our ovaries have an increased likelihood of producing multiple eggs during a cycle because after age 35 we produce more follicle stimulating hormone.
  • Also, women who have more children have more multiples.  In some ways that’s just a matter of numbers but it may also be because women with many children are quite fertile and ovulate well.
  • Moms who have already had multiples are twice as likely to have twins or multiples again.
  • Women with a higher BMI (body mass index) and who consume more fat in their diets have a greater chance of multiples.  Conversely, women who are vegans or vegetarians have less multiples.
  • Twins are more common in Caucasian and African-American women than Hispanic and Asian women.
  • Location matters too, possibly due to climate and diet. Twins are more common in Western Europe and Nigeria but less common in Southeast Asia.
  • Fertility drugs stimulate the ovaries to release eggs, which can cause the release of multiple eggs.  Women may take fertility drugs for many reasons and they may combine them with other fertility treatments that also increase the chance of multiples.
  • IVF (in vitro fertilization) increases a woman’s likelihood for multiples quite a bit depending on her age.  IVF entails implanting one or more embryos in a woman’s uterus.  The more embryos that are implanted, the more of a chance she has to have multiples.