Seeing if Multiple Pregnancy is Identical or Fraternal Twins

If you are gestating two babies, you will probably be interested in finding out if the babies are identical twins or fraternal twins. In some cases, it is possible to find out for example, if it is detected that they are different sexes and this will indicate that they are fraternal twins; but if they are the same sex, they can either be identical or fraternal twins.

If the doctor is not able to see the sexes of the fetuses or if the babies are the same sex, there are other ways of finding out if they are identical, here are some of the ways:

• An ovule that is divided very soon after fertilization in the first two or three days will result in embryos that have separate placentas and independent amniotic bags. In the sonogram though you cannot see if the fraternal twins came from two fecundated ovules separately. 

• If the ovule divides between the third and the eighth day after fecundation, the resulting twins will be in two separate amniotic sac separated but will share the same placenta. If the in the sonogram the doctor can see that the two babies are sharing the same placenta, it probably means they are identical. However, do keep in mind that it is sometimes hard to determine with a sonogram if there is only one placenta and both babies are very close to each other. The thickness of the membranes that separate the sac offers another key though, and when there are two placentas, the membrane that separates it is thick, and when there is only one placenta, the membrane is very thin. 

• An ovule that separates between the eighth and thirteenth day after fecundation, results in twins that not only share the same placenta but are also in the same amniotic sac. If the doctor does the sonogram and is able to see that the babies share the same amniotic sac, he or she can be certain that they are identical. This is not a very common incidence though.

• An ovule that divides after the thirteenth day of gestation has as a result Siamese’s, which is something that is very rare.

An ultrasound expert will be able to take advantage of the subtle indications in order to differentiate the different types of double pregnancies. Even though these cases are always concluding, there are cases in which this is not so. The doctor will first establish if the babies have two placentas or not and if they are fraternal or identical twins. Establishing the type of placentation is easier in the first three months of pregnancy and more difficult in the second and third term.

Remember that since double pregnancies are associated with risks and problems, it is important to establish what type it is. If the indications of the sonogram are ambiguous and the medical situation suggests that it would be important to determine what type of double pregnancy it is, you can get an amniocentesis to obtain the answer.