One of the most popular topics on my site is the chances of having twins. As the Guide to Parenting Twins & Multiples at About.com, I frequently receive emails similar to the following:
"I was just wondering if you could help me figure out what the odds of me having twins are? My grandmother is a fraternal twin and my grandfather is a fraternal twin, then they had my mom and her two brothers (none are twins). My mom had me and my sister but not twins, are we more likely to have twins because of this?"
"My great grandmother was a twin, my father is a twin and I was a twin (however it miscarraged early on in my mothers pregnacy) so i was just curious to see if it is likely if I will have twins as my partner and I are wanting to start trying to have a baby soon."
"My boyfriend and I are discussing having children, but we are confused because he is a twin (nonidententcal). I was meant to be a twin (boy/girl) but he didnt make it and there is a lot of conflicting infomation on the Internet. My dad is also a boy/girl twin. It does run in both our families, but some sites say that does not matter. I guess we would just like to know the percentage, if at all, if we would have twins. He does not mind suprises, but I don’t handle them well hahahaha, so if I knew there was a chance (of twins), I wouldn’t be so shocked if it happens."
Readers often visit my site wanting to know if I can tell them whether they will have twins. Sometimes these emails make me giggle. I am not a fortune teller. I don't have a crystal ball. There is no way to predict who will or won’t have twins, any more than there is a proven method for picking winning lottery tickets, betting on horses, or playing the numbers in Las Vegas. Believe me, if I had such prophetic powers, I would probably be in a different line of work, say the stock market.
The Chances of Having Twins
Facts and figures about twins and multiples abound. There is plenty of statistical data and information about twinning and the multiple birth rate. However, It is important to recognize is that these numbers are based on populations -- not individuals. For example, we know that the multiple birth rate in the United States is 32.6 per 1,000. We know that the rate varies from year to year, and within different groups of people. For example, geographic and racial populations show varying rates of twinning; the rate is lower in Asia and higher in parts of Africa. We also know that certain factors influence twinning, such as fertility treatments, maternal age, family history, and body composition.
The numbers become even more confused because there are different types of twins, and the rates are different based on zygosity. The generally accepted multiple birth rates are based on all twins and do not distinguish between monozygotic (identical) and multizygotic (fraternal) twins. However, the rate is vastly different, with monozygotic twins being significantly more rare.
All of these statistics apply to groups of people - the population of the United States, residents of Nigeria, women over the age of 40, etc. If you are reading this article, you are probably wondering “What are my chances of having twins?” The only specific information that I can provide is the same statistic that applies to everyone: 32.6 per 1,000, or about 1 in 30. That number may tweak up or down depending on your personal circumstances and factors such as your age, weight, family history, previous pregnancies, diet, ovulation patterns and reproductive treatment. But it is impossible to calculate an exact figure that would accurately predict the outcome for you. There is no surefire way to know whether you will have twins.
Will I Have Twins?
That being said, if it is your intent to have twins, or if you are simply very curious as to whether there will be twins in your future, there are some factors that increase or decrease your chances. These include:
- having a history of twinning on the mother’s side of the family
- taking fertility enhancing drugs or undergoing reproductive assistance that includes multiple eggs or embryos
- having a Body Mass Index (BMI) of 30 or above
- being in the top 25th percentile for height
- being over the age of 45
While these factors may make it more likely that you will have twins, they don’t indicate a certainty that you will have twins. You can take quizzes, scan the Internet for information, or email experts for their opinions, but unfortunately, you will just have to take your chances and wait to see what the future holds for you. There is certainly plenty of information on my site about twins and multiples, and I invite you to explore it and learn more.