Overview of Multiple Pregnancy

Overview of Multiple Pregnancy

What is multiple pregnancy?

A multiple pregnancy is a pregnancy
with 2 or more babies. Some names for these are:

  • Twins for 2 babies

  • Triplets for 3 babies

  • Quadruplets for 4 babies

  • Quintuplets for 5 babies

  • Sextuplets for 6 babies

  • Septuplets for 7 babies

Multiples make up only about 3 in 100 births, but the multiple birth rate is rising.
According to the National Center for Health Statistics, the twin birth rate has risen 70%
since 1980. It is now 32.6 per 1,000 live births. The birth rate for triplets and
other higher-order multiples rose dramatically. But it has slowed since 1998.

What causes multiple pregnancy?

Many factors are linked to having a multiple pregnancy. Naturally occurring factors
are:

  • Heredity. A family history of multiple pregnancy
    raises the chances of having twins.

  • Older
    age. 
    Women older than 30 have a greater chance of multiple conception.
    Many women today are waiting to have children until later in life. They may have
    twins as a result.

  • Past
    pregnancies.
     Having 1 or more previous pregnancies, especially a multiple
    pregnancy, raises the chances of having multiples.

  • Race. African-American women are more likely to have twins than any other
    race. Asian Americans and Native Americans have the lowest twinning rates. White
    women, especially those older than 35, have the highest rate of higher-order
    multiple births (triplets or more).

Other factors that have greatly raised the multiple birth rate in recent years are
reproductive technologies such as:

  • Ovulation-stimulating medicines. These include clomiphene citrate and
    follicle stimulating hormone (FSH). These help produce many eggs. If fertilized,
    they can result in multiple babies.

  • Assisted reproductive technologies. In vitro fertilization (IVF) and
    other methods may help couples get pregnant. These technologies often use
    ovulation-stimulating medicines to produce multiple eggs. These are then
    fertilized in the lab and returned to the uterus to grow.

How does multiple pregnancy happen?

Multiple pregnancy often happens when more than 1 egg is fertilized and implants in
the uterus. This is called fraternal twinning. It can produce boys, girls, or a combination
of both. Fraternal multiples are simply siblings conceived at the same time. But just
as siblings often look alike, fraternal multiples may look very similar. Fraternal
multiples each have a separate placenta and amniotic sac.


Illustration of a twin birth, head down/head down

Sometimes 1 egg is fertilized and
then splits into 2 or more embryos. This is called identical twinning. It makes all
boys, or all girls. Identical multiples are genetically the same. They often look
so
much alike that even parents have a hard time telling them apart. But these children
have different personalities and are distinct people. Identical multiples may have
individual placentas and amniotic sacs. Most share a placenta with separate sacs.
Rarely, identical twins share 1 placenta and a single amniotic sac.


Illustration of a twin birth, head down/head down; 1 placenta, 2 cords