The number of multiple births has increased with the introduction of various pregnancy inducing methods and highly researched medications. If statistics are to be believed, in the last decade, there has been a 65% increase in the number of multiple births.
If you are pregnant, you may want to take extra care of yourself just in case you are having twins. For those who have had medication to improve fertility, there are good chances of giving birth to twins or multiple babies...
...However, for those who’ve naturally got pregnant, an unusual weight gain during pregnancy, extremely large uterus, incessant fatigue and extremely varied mood swings are indications of multiple births. In addition to that, you may also feel a heavy pressure in the groin area and severe nausea.
Due to the twin fetal development, the weight gain in each of the trimesters is significantly more than in the normal single pregnancy. In a multiple pregnancy, in the first trimester, you may gain five to ten pounds, in the second trimester ten to fifteen pounds and in the third trimester, fifteen to twenty pounds.
There are in fact two kinds of twin pregnancies. One is the Dizygotic twins, also known as fraternal twins. These are formed when two different oocytes get fertilized by two sperms and therefore two different zygotes and subsequently, embryos are formed. These twins are non identical because they are formed from two different zygotes. The other kind of twin pregnancy is monozygotic. This is the identical twin fetal development in which a single zygote divides into two during the development of the eggs and therefore twins, who look identical to each other, are formed. See also twin pregnancy week by week
Though a dizygotic pregnancy occurs at the time of conception itself, a monozygotic pregnancy occurs when the zygote splits into two. This usually occurs in the first eight days after the initial conception. If the zygote is not able to completely split in the first eight days, the twins formed are conjoined.
In a complication that could arise in a twin pregnancy, one of the twins begins to depend on the other for nutrition and becomes parasitic, robbing the other twin of its nutrition. One of the twins may completely stop developing in such a case.
There could also be a chance that one of the monozygotic twins begins to develop in a different manner, therefore becoming different from the other twin. In such a case, the twins are only half or semi identical and not completely identical.