What increases the chance of having a twins
Several factors can increase the likelihood of a woman conceiving twins. These include:
A woman has a 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. Yet, 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 have twins if one of their grandparents did. Yet, there is little evidence to support this theory.
The ASRM notes 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.
Many pregnancies carry extra 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.
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 non-identical 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
In the U.S., Hispanic women are less likely to have twins than non-Hispanic white women or black women, according to the ASRM.