Have you noticed more twins in the world recently? A rise in fertility treatments and older women having babies has lead to increased multiples nationwide. In this article we will discuss what causes multiples to be born and how to take care of yourself if you are expecting more than one baby.
Types of Multiples
- Identical Twins: Identical twins, or monozygotic twins, occur when a fertilized egg splits into two parts. This causes two embryos with the same DNA to develop. It is unknown why a zygote splits into two identical embryos. However, the occurrence (3 in 1,000) is the same across all populations.
- Fraternal Twins: Fraternal twins are also known as dizygotic twins. They are formed when two eggs are fertilized by two separate sperm. Although uncommon, women can release more than one egg during ovulation, resulting in two eggs getting fertilized. This results in two embryos that share approximated 50% of their DNA, the same amount seen in siblings. Fraternal twins are twice as common as identical twins.
- Supertwins: Supertwins is a name commonly used to describe higher-order multiples such as triplets, quadruplets, and quintuplets. Higher-order multiples can be caused by one egg splitting into 3 or more, 3 or more eggs being fertilized, or by a combination of these phenomena.
What causes a woman to conceive multiples?
There are a couple factors that have been shown to increase a woman’s chance of having multiples. The most common cause is fertility treatment, which often causes a woman to release more than egg during ovulation, leading to fraternal twins. The probability of having multiples increases after 30 years of age. Heredity can increase a woman’s chances of having fraternal twins, though identical twins are not influenced by heredity. A relationship between obesity and twins has been established. Lastly, African American women are the most likely to have fraternal twins, while Asian women are the least likely.
What are the risks associated with multiple births?
Diagnosing multiples is important for pregnant women. Mothers of multiples require more prenatal care to monitor the health of the babies and the mother.
The biggest risk with multiple births is premature birth. 60% of twins, 90% of triplets, and almost all higher-order multiples are born premature. An average pregnancy lasts 39 weeks. Twins, on average, last 35 weeks, and triplets, on average, last 32 weeks. Quadruplets average 29 weeks. Premature babies are at high risk for multiple problems.
Low birth weight is another problem commonly seen in both premature and full-term multiples. Low birth weight poses multiple health risks for early development and can have lead to disabilities such as cerebral palsy.
Mothers of multiples are at higher risk for gestational diabetes and preeclampsia. Both of these can be dangerous to both mother and baby, and need to be regularly monitored for and managed.
In Part 2, we will discuss the special care that is required for mothers having multiples and ways to stay healthy during a multiples pregnancy.