Published October 24, 2007 by
Twins. We're familiar with the term, we're familiar with purchasing twins baby gifts, but what else do we know? Well, twins occur once in eighty-eight births; and quadruplets once in about 680,000 births. Other denominations of multiple births occur quite rarely. Multiple births occur more commonly in older women; women who had at least one pregnancy; women who have a family history of multiple pregnancy an the mother’s side of the family; and women who have taken fertility drugs to stimulate ovulation [the expulsion of an egg from the ovary].
Types of Twins
There are two types of twins. One type starts from a single egg, which divides in two very early after fertilization. Because a single egg is fertilized by a single sperm before this division, the two offspring will be of the same sex and alike in skin, hair, and eye color and in general appearance. They are called identical twins.
An extremely rare form of twinning is called conjoined or Siamese twinning. In these unfortunate cases. The twins are attached to each other at the head, chest, abdomen, or back. Surgical separation of Siamese twins may be successful, but often results in the death of one or both babies.
The other type of twinning is the fertilization of two eggs by two different sperm. Twins of this type- called fraternal twins-may be of the same sex or opposite sexes and will bear no greater resemblance to each other than any other brothers or sisters. Most twins that result from fertility drugs are of this type.
Approximately one third of twins are identical, and two thirds are fraternal.
One or more eggs may involved in other forms of multiple pregnancy. For example, quadruplets may result from one, two, three, or four eggs.
In most cases of multiple births, the cause is unknown. Why certain families have many sets of twins is also not understood. Fertility drugs used to stimulate ovulation are often associated with multiple births-sometimes up to seven or eight fetuses.
Doctor and patient alike will often suspect multiple pregnancy when the woman’s uterus grows more rapidly then would be expected with one pregnancy. This suspicion is confirmed if the doctor hears two separate fetal heartbeats, or if an ultrasound scan shows two or more fetuses.
The major complication of multiple pregnancy is premature labor, with the delivery of small, premature babies that are not yet ready to live outside the mother’s body. In general. The more fetuses the woman is carrying, the earlier she is more likely to go into labor. Other complications that may affect the mother are anemia and pre-eclampsia.