As a survivor of a twin pregnancy with the happy outcome of two bouncing baby girls, I have a special interest in multiple pregnancies. I learned that a twin pregnancy was the result not just of fertility but of fecundity.
Being fertile meant I could conceive. Being fecund apparently meant I could do it with more than one egg at a time.
Multiple pregnancies can hand you babies that are the equivalent of identical twins which come from the same fertilized egg which has split into two -- or more -- or fraternals each of whom had their own individual egg.
Those from the same egg will also have identical DNA and are usually (though not always) the same sex. Fraternals will be no more alike than any other siblings, though people may not believe you on this.
The fact that they are the same age somehow seems to make them look more alike than the usual situation where there may be a year, or two or more, between them.
The most common form of multiple birth is the birth of twins. Triplets would be runner-up.
In a set of triplets, you might have two identicals and one fraternal, or you may have three fraternal babies. Occasionally you may have three identicals.
But other multiple births do occur. In a set of quadruplets, there may be the equivalent of two sets of twins, one set of twins and two fraternals, or four fraternals.
Rarely, you may find yourself with four -- or more -- identical babies staring at you. If this is your situation I wish you well.
The greatest number of babies born alive in a multiple birth have been a few sets of nonuplets, or nine babies. Some pregnancies have commenced with more fetuses but no live births.
Usually multiple pregnancies of this magnitude are the result of fertility medications and assisted reproductive technology (ART).
The number of multiple births has increased dramatically since 1980. The two main factors for this seem to be childbearing in older women and use of fertility treatments.
Women into their late 30's or their 40's are more likely to have multiple births.