What increases the odds of having twins?

Woman holding twin girls


By Claire Sissons     


Reviewed by Valinda Riggins Nwadike


Why do twins happen? | Are twins
common? | What increases the chance | Increasing the chance | Summary


There are many myths about how
to improve the odds of having twins. Although there are no proven ways to
increase the likelihood of conceiving twins, there are certain factors that can
make this type of pregnancy more likely.


Twins can occur either when
two separate eggs become fertilized in the womb or when a single fertilized egg
splits into two embryos.
Having twins is more common
now than it was in the past. According to the Centers for Disease Control and
Prevention (CDC), twin births have nearly doubled over the last 40 years.
A woman has a higher chance of
having twins if she conceives with the assistance of fertility treatment or is
aged 35 years or over. In the United States, fertility treatments account for
more than one-third of twin pregnancies.
In this article, we explore
why twin pregnancies occur, how common they are, and factors that can make them
more likely. We also explain whether a person can increase their chance of
having twins.

Why do twin pregnancies
happen?


Doctors do not fully
understand the reasons why twin pregnancies sometimes occur. However, some
factors can increase the likelihood of giving birth to twins, including:

  • the woman’s age
  • having a family history of
    twins
  • having fertility treatments
Conception happens when a
sperm fertilizes an egg to form an embryo. However, if there are two eggs
present in the womb at the time of fertilization or the fertilized egg splits
into two separate embryos, a woman can become pregnant with twins.
There are two types of twin:

  • Identical twins: This type of
    pregnancy happens when a fertilized egg splits into two separate embryos. These
    embryos are monozygotic, which means that they have identical genes. Identical
    twins are the same sex as each other and look very alike.
  • Nonidentical, or fraternal, twins:
    This type of pregnancy occurs when there are two eggs present in the womb at
    the time of fertilization, and sperm fertilize both of them. These embryos are
    dizygotic, which means that they do not have identical genes and may not be the
    same sex.
Fraternal twins are common
after fertility treatment because healthcare professionals often place two
fertilized embryos into a woman’s womb to increase the chances of a successful
pregnancy.
How common are twins?

Twins are relatively uncommon.
According to the American Society for Reproductive Medicine (ASRM), only
approximately one in 250 pregnancies results in twins.
However, the birth of twins
has increased significantly alongside the rise in the use of fertility
treatments and with more women choosing to have children at a later age. Since
1980, the birth rate of twins has increased by more than 75 percent.
A woman is more likely to have
fraternal twins than identical twins. Identical twins account for only about
one-third of multiple pregnancies.

What increases the chance of
twins


Several factors can increase
the likelihood of a woman conceiving twins. These include:

Family history

A woman has a slightly higher
chance of having twins if she has a family history of twins. A family history
of twins on the mother’s side increases this likelihood more than a family
history on the father’s side. However, this only applies if conception takes
place without the use of fertility treatments.
According to the ASRM, women
who are themselves nonidentical twins produce twins in around 1 in every 60
births. For men who are nonidentical twins, the chance of conceiving twins is
only 1 in every 125 births.
Some people believe that twins
can skip a generation, meaning that a person will potentially have twins if one
of their grandparents did. However, there is little evidence to support this
theory.

Fertility treatment

The ASRM note that the main
factor that increases the chance of having twins is the use of fertility
treatments. The various types of fertility treatment available increase the
likelihood of twins in different ways.
Some fertility drugs work by
stimulating a woman’s ovaries, which can sometimes cause them to release more
than one egg. If sperm fertilizes both of these eggs, this can result in twins.
In vitro fertilization (IVF)
can also increase the chance of conceiving twins.
Healthcare professionals carry
out IVF by extracting a woman’s eggs and fertilizing them with a donor’s sperm
in a laboratory to produce an embryo. They then transfer the fertilized embryo
into the woman’s womb.
To increase the likelihood of
success, the healthcare professional may place more than one embryo into the
womb. Twins can occur if both embryos implant and develop successfully.
Multiple pregnancies carry
additional risks, so the healthcare professional will usually limit the number
of embryos that they transfer to the woman’s womb to reduce the chance of a
pregnancy with twins, triplets, or more.

Age

According to the Office on
Women’s Health, women who are aged 30 years or older are more likely to
conceive twins. The reason for this is that women of this age are more likely
than younger women to release more than one egg during their reproductive
cycle. If sperm fertilizes two separate eggs, a twin pregnancy can occur.
Height and weight

The ASRM report that
nonidentical twins are slightly more common in taller or heavier women than
they are in small women. The reasons for this are not clear, but it may be due
to better nutrition. Women with a higher body weight may have more resources
available for a developing fetus.
Racial background

In the U.S., Hispanic women
are less likely to have twins than non-Hispanic white women or black women,
according to the ASRM.

Increasing the chance of twins

There are many unproven claims
about how to increase the likelihood of conceiving twins. Some people advise
following specific diets or using certain alternative therapies, but there is
no scientific evidence to support these methods.
Fertility treatments, particularly
IVF and ovary stimulants, do increase the chances of having twins. However, a
twin pregnancy is riskier for both the woman and the developing fetuses. For
this reason, some fertility clinics advise against implanting multiple embryos
during IVF treatment.
The CDC recommend that younger
women who are having their first fertility treatment select just one embryo for
transfer to their womb.
As the success of fertility
treatment is improving, there is often less need to transfer more than one
embryo. In the U.S., the number of IVF treatments involving the transfer of
three or four embryos decreased significantly between 2007 and 2016.
Transferring just one or two embryos reduces the likelihood of a multiple
pregnancy.
A twin pregnancy increases the
risk of:

  • premature birth
  • low birth weight
  • stillbirth
  • disabilities at birth and
    congenital health conditions, such as cerebral palsy and autism
  • preeclampsia
  • diabetes during pregnancy
  • cesarean delivery
  • needing bed rest while
    pregnant
Summary

Although certain factors
increase the chance of having twins, there is no way to improve the odds of
having twins naturally. A woman will usually find out that she is pregnant with
twins from an ultrasound early on in the pregnancy.
Some symptoms may indicate a
twin pregnancy, including more intense morning sickness and very rapid weight
gain. Regular medical appointments will improve the chances of a healthy
pregnancy.


SOURCE: MEDICAL NEWS TODAY
Kayode Ojo
Kayode Emmanuel Ojo is the Co-Founder and Managing Director at SHEFFA Limited. He is presently studying Computer Science at the National Open University, Victoria Island, Lagos.