Twins, Triplets, and More

Overview

Greek mythology and the Bible give early examples of multiple births. Romulus and Remus were twins raised by the mother wolf. Esau and Jacob were the twin boys of Rebekah and Isaac. The overall spontaneous twinning rate is 1.2 per 100 live births, the rate varies depending on the type of twins. Triplets occur 1 per 6,889 and quadruplets 1 per 575,000 births. These statistics do not include pregnancies that have an early loss of one baby. Home pregnancy tests and the use of ultrasound have demonstrated a greater number of multiple pregnancies than quoted. So, if you are diagnosed with a multiple pregnancy early on (four to six weeks) be aware of the possibility of loss. Once a normal heartbeat and normal growth or size have been confirmed, your chances for this type of loss decrease considerably.

Your chance for having a multiple birth varies depending on whether the babies are from one egg that splits or from separate eggs, if you've taken infertility drugs, or if multiple embryos were implanted. Identical twins develop from the fertilization of a single egg which later divides into two babies. These children look identical because they have the same genetic makeup. The rate of having identical twins has remained fairly constant at one twin birth per 85 live births. Your chance of having identical twins is the same no matter your age, the number of babies you have had, your race, if you took infertility medications, or if you were a twin yourself.

Fraternal multiples develop when the mother releases more than one egg, and these eggs are then fertilized by different sperm. You are more likely to have a multiple pregnancy as you become older until the age of thirty-five when your chances decrease. The following also increase your chances of a multiple birth: if you have had three or more pregnancies, if you are a twin yourself, if you are tall and large, if your race is African-American, if you are using infertility drugs, or if you are having multiple embryos implanted. Interestingly, Nigeria has the highest rate of twin births, and Japan has the lowest rate.

The use of the fertility drug Clomid increases your chance of having twins to 8 per 100, triplets to approximately 0.5 per 100, and quadruplets to 0.3 per 100. Pergonal, another fertility drug, increases your chance even further. The twinning rate jumps to 18 per 100, triplets 3 per 100, and quadruplets to 1.2 per 100. Assisted reproductive technology (ART) is a term used to describe procedures like in vitro fertilization (IVF), gamete intrafallopian transfer (GIFT), zygote intrafallopian transfer (ZIFT), and similar infertility procedures. Years ago, children born as a result of ART were called "test-tube babies." When ART involves multiple eggs or fertilized ovum, your chances of having multiples increase slightly above Pergonal use: 22 per 100 for twins, 4 per 100 for triplets, and 1.2 per 100 for quadruplets.

In pregnancies with triplets or more, the babies can all be identical, fraternal, or have a mixture of both. This mixture of fraternal and identical occurs when multiple eggs are released and fertilized and one or more of these fertilized eggs divides into two or more separate babies.