Did you have a shock of a lifetime when your sonographer told you that you’re having twins on your first ultrasound? My husband and I surely did!

WHAT IS THE DIFFERENCE BETWEEN FRATERNAL AND IDENTICAL TWINS?

Fraternal twins or dizygotic twins come from two

The ability to release multiple eggs during ovulation is hereditary. As a woman, if you have blood relatives that have had fraternal twins, your chances are fairly high that you will also conceive fraternal twins. With advancement in assisted reproductive techniques, twins make up about 90% of multiple births.

Identical twins or monozygotic twins result in only one egg being fertilized by one sperm. Sometime during the first couple of weeks of cell division, the egg splits into two different, but genetically identical eggs. Identical twins are always the same sex. Unlike fraternal twins, the ability to conceive identical twins is not hereditary. It is completely by chance, that this happens, though there are several things that increases the chances of having twins:

• Advanced maternal age,
• Race (Black African women have the highest incidence and Asians have the lowest incidence),
• Heredity,
• Use of Fertility drugs. 

In my experience, I am a woman of Asian decent, in my early 30’s and have not used any fertility drugs and have no history of any twins in my side of the family. According to my obstetrician, the incidence of conceiving my identical twins is less than 1%. With all the shock and fear and complication with having twins, my husband and I and our families feel absolutely blessed.

HOW DO YOU KNOW WHICH ONE YOU HAVE?

• PLACENTA: 

The sonographer will be able to tell you if there are two placentas or one. Fraternal twins have their own placentas, and of course are enclosed in their own amniotic sac.

Identical twins share one placenta, though this may not be so easy to determine on the first ultrasound, because it is possible for two placentas to look fused and appear to be only one. The babies may share one amniotic sac, or they may be in their own amniotic sacs.  In later ultrasounds, the thickness of the amniotic sac can also indicate whether the twins are identical, as the sac is very very thin in identical twins. 

• SEX

 If you find out that you have one boy and one girl, then they are of course fraternal twins.

• You never know until birth

In some cases, women do not know until after birth whether they have identical or fraternal twins. The obstetrician will examine the placenta to see if there is truly one or if there are two fused placentas. If it is not obvious, or if parents want to be 100% sure, genetic testing can be done. There are genetic companies that will send you a swab kit to use on the babies mouths and for a small fee, you send it back and a several days later, they will send you the result.