What are your chances of having twins? Well, on average, about 1.6 percent of pregnancies result in twins. So… the odds aren’t exactly with you.
Or are they?
Turns out, there are a number of factors that can affect your odds of getting pregnant with multiples and having twin babies. These include your age, diet, number of pregnancies you’ve had, ethnicity, location, body type, and more.
So what are your chancing of having twins or multiples?
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What is the birth rate for twins?
Identical twins rates are equal to about 3.5 out of 1000 births, the birth rate for identical twins has not changed over the past few decades and is about the same nationwide.
Worldwide, about 12-16 in 1000 people are naturally conceived twins. So, the chances of having twins are small. However,in 2010, births of twins in general in the U.S. were 33 in 1000 people. The birth rate for fraternal twins has risen by about 76% in the past 30 years. The obvious reason is fertility treatments but surprisingly, they are not the only reason.
What factors affect the chances of having twins?
The chances of a woman having identical twins are about the same for everyone, as identical twins do not tend to run in families. This is because identical twins come from a single fertilized egg splitting in two and this is a random, rare event.
Fraternal twins, on the other hand, can be genetic. Fraternal twins come from two separate eggs being fertilized by two sperm. Typically women only release one egg each cycle but women who conceive fraternal twins have released two. This is why fraternal twins can only be genetically connected through the mother, meaning the father’s genetics have nothing to do with twinning.
Releasing more than one egg in a cycle is called hyper-ovulation and is controlled by certain genes. Women who conceive fraternal twins usually have high levels of these genes, which makes sense.
So who is more likely to conceive fraternal twins? Your chances of having twins depend on six factors:
1. Body type
Twins tend to be more common in larger women as well as woman who are tall. In one study, women with a BMI of 30 or above were nearly 1.5 times more likely to have twins than the women in the normal BMI range of 20 to 24.9.
Those same women were more likely to have opposite sex twins than same sex twins as well. Researchers are still unsure why this is the case.
2. Ethnicity and location
On the surface it appears that ethnicity plays a role in the chances of having twins, yet location seems to have a large part as well.
The Yoruba tribe of Nigeria has the highest rate of twins at 45–50 twin sets (or 90–100 twins) per 1,000 live births, however being of Nigerian decent and living elsewhere doesn’t show the same correlation to twin births.
In Central Africa there are 18–30 twin sets (or 36–60 twins) per 1,000 live births. North America and Europe (and caucasians in general) have intermediate rates of 9-16 twin sets per 1,000 live births Latin America, South Asia, and Southeast Asia (and hispanic and asian ethnicities in general) have the lowest rates of 6–9 twin sets per 1,000 live births.
The difference in chances of having twins between geographic locations (more than ethnicity) begs the question of whether climate, diet, or lifestyle have more to do with the chances of having twins than anything else.
We already know that diet does play a role. Women who eat full fat foods over non fat or low fat are more likely to conceive twins. This could be because fat is an important building block for pregnancy and those that eat more fat are better suited to carry two babies. It may also be that the difference in the amount of fat a woman eats affects hormones.
Some information points to the daily consumption of yams being the reason Nigerian women have more chances of having twins. True yams contain a phytoestrogen that increases a woman’s follicle stimulating hormone (FSH), and may cause hyper-ovulation.
4. Maternal Age
Older woman tend to have a higher chance of fraternal twins. Women over 35 tend to produce more FSH than younger women and women with higher levels of these hormones are more likely to have twins.
The increase in FSH levels also shows declining fertility, which means they are less likely to get pregnant, but more likely to have twins if they happen to conceive.
5. Number of Pregnancies
The more pregnancies that a woman has had increase her chances of having twins. This could be a simple case of numbers. The more pregnancies you have the higher your chances of having twins.
6. Fertility Treatments
Women who take certain types of fertility treatments have increased chances of having twins. In vitro fertilization (IVF) increases your odds of having multiples by 20-40% depending on how many embryos are placed inside your womb. Some believe that IVF can also increase your chances of having identical twins but research doesn’t support this.
Fertility drugs increase the odds of you releasing several eggs at the same time by stimulating your ovaries. These kinds of drugs increase your chances of having twins or multiples to 10% or higher, up to as much as 30%.
Why twins are more common these days
What has caused the rise in multiples? One possibility is that women are waiting until they are older to have babies. As we mentioned earlier, older women have higher chances of releasing more than one egg in a cycle, thus, increasing their chances of having twins.
Another reason behind the rise in twins is the increased use of fertility drugs and other ways to assist a woman’s odds of conception. In the 1970’s when fertility treatment started becoming reliable, the incidence of twins almost doubled.
Over the past decade, the rise in twins has steadied. This is probably due to the fact that fertility treatments have become more advanced and have lowered the risk for multiples while keeping the high possibility for conception.
How will I know if I’m having twins?
There are physical indicators like showing earlier than normal and higher HCG levels. Some women who have been pregnant with twins report higher than normal levels of morning sickness. However, an ultrasound is the only way to be sure. An ultrasound can usually detect twins as early as 8-14 weeks gestation.
How about you?
Did you dream of having twins while you were (or currently are!) pregnant? Do you think you could handle having twins? Share with us in the comments below!