Twins are a fascinating phenomenon. And, as modern technology has allowed humans to have greater control over fertility, they are also becoming more common. In fact, during 1997, there were more twins born to women in their upper-40s than there were throughout the entire decade of the 1980s. There are a myriad of myths and mistaken information about twins out there and, if you have recently found out you are expecting twins, you’re probably searching for all the information you can.

Here are interesting, accurate, facts about twins, some of which might surprise you.

1. The difference between identical and fraternal twins. Identical twins occur when a single egg splits into two separate zygotes. These babies share the exact same genetic information. You may have heard identical twins always share the same amniotic sack. This is not necessarily true. There are occasions when the egg splits so early in its development that two separate sacs form. Fraternal twins are born when the mother releases two eggs, and a separate sperm fertilizes each one. In other words, fraternal twins are the same thing as two separate siblings being born in the same womb at the same time. If twins are a girl and a boy, you know 100% they are fraternal. However, same-sex twins have to be tested genetically to be absolutely sure.

2. More pregnancies than we thought start out with twins. One thing that surprised doctors with the advent of early fetal monitoring is that more pregnancies than we thought start out with twins. However, it is common for one of the twins to be absorbed by the womb within the first 12-weeks. A woman may experience spotting or bleeding as a result. This is called vanishing twin syndrome, and has no negative effect on the surviving twins.

3. Your chances of having fraternal twins escalate as you get older. Women 30-years and older have a higher chance of having twins. As your fertile years begin to wane, you produce higher levels of FSH, a hormone required to stimulate your follicles to start mature and egg. In some cases, the follicles can be over-stimulated, which causes the ovaries to release two eggs instead of one. The grand irony is that elevated FSH levels are also associated with lower fertility rates.

4. Fraternal twins run in families. If you have a set of fraternal twins in your family, you are more likely to have a set of twins yourself. This is because the propensity to release two eggs, rather than one, is genetic. Interestingly, identical twins don’t run in families. If you and your partner both have twins in the family, your chances are even greater. This is because a healthy sperm count and strong sperm motility are also genetic. You may have heard the myth that “twins skip a generation.” So far, there is no evidence to support this. African-American women are the most likely to conceive fraternal twins, while Asian-Americans are the least likely have them.

5. Fertility treatments increase your chances of having twins. Many of the drugs associated with fertility treatments are designed to stimulate egg production and release. Also, treatments like IVF are most successful when the doctor implants more than one embryo into the womb. If one or more of the healthy embryos attach successfully, you’ll find yourself the proud parents of twins or multiples.

If you are pregnant with twins, it is critical that you receive early pre-natal care as your diet, activities and pregnancy will need to be more carefully monitored. Contact Overlake OB/GYN to make an appointment. We look forward to caring for all three of you!