What Are My Chances Of Having Twins?

If you are in early pregnancy, or trying to conceive, you may be wondering what the chances are that you will carry a twin or multiple pregnancy. Twins and multiples are becoming more common everyday with the increased use of fertility drugs and assisted reproductive technology (ART). These treatments are known to increase the chances of twin and multiple pregnancies.

Today, one in every 32 births results in twins. This represents an increase of 65% since 1980. As for women who conceive twins without availing themselves of fertility drugs and treatments, the rate is one in 89 births.  

Much more striking is the significant rise in higher-order multiple births. The rate for triplets and higher-order births rose by more than 400% between the years1980-1998. While still significant, the rate is now falling a bit as researchers refine fertility treatments and techniques. During the year 2003, for instance, one in every 535 births resulted in triplets or higher-order multiples.

Identical Twins

One number that remains consistent throughout the decades is the possibility for giving birth to identical twins in which a fertilized egg splits into two halves (monozygotic). The statistic remains constant worldwide at 3-5 in every 1,000 births.

Drugs that stimulate your ovaries can cause the release of several eggs at once. 20% of women taking gonadotropins will become pregnant with twins or multiples. Women who conceive while taking Clomid have a 5%-12% likelihood of bearing twins.

In vitro fertilization (IVF) increases your chances of a multiple pregnancy to between 20%-40%, depending on the number of embryos implanted in your womb. Gamete intrafallopian transfer (GIFT) and zygote intrafallopian transfer (ZIFT) also tend to result in more than one fetus per pregnancy.

IUI (intrauterine insemination) doesn't increase the rate for the conception of multiples but since this treatment is often combined with fertility drug treatment, there is a concurrent rise in the conception of multiples.

Fraternal Twins

While these treatments do increase your chances for having fraternal twins, or two eggs fertilized by two sperm, the first evidence has begun to trickle in, suggesting that such treatments also increase the rate for the conception of identical twins.

Here are some other factors that can increase the chances that you will have twins or multiples:

*Family History—If you are a twin, or there are twins in your family, you have a greater chance of having twins. Female fraternal twins have a one in 60 chance of having twins.

*Race—African Americans have more twins than Hispanics or Asians.

Declining Fertility

*Age—Older women have a higher chance of having twins and multiples. One 2006 study demonstrated that women over the age of 35 have higher levels of follicle stimulating hormone (FSH) than do younger women. While in general, this is a sign of declining fertility, if older women do become pregnant, they have a greater chance of conceiving twins.

*Numerous pregnancies—The more pregnancies you've sustained, the more likely it is that you will have twins.

*Twin History—Once you've birthed fraternal twins, your chance for conceiving another set doubles for future pregnancies.

*Body type—Large, tall women are more likely to have twins than small women.

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