If you have these genes , your chances of fertilizing two different eggs by two different sperm increases, resulting in fraternal twinning. Are twins on the mom's side in all instances? According to Science Mag, there are multiple factors at play in the creation of twins. They wrote, "In vitro fertilization, for which demand has surged, is more likely to yield twins.
Older women, who are having more children than in the past, are also more likely to release more than one egg , increasing their chances of giving birth to fraternal twins. Age and genetics are important, but apparently, so is race.
According to an article in The New York Times, "Twin births have historically been more common among non-Hispanic black women.
Twins are tricky. If you're older, if you're getting IVF, if you're a woman and either of your parents have fraternal twins in their family tree, or if you're black, or some combination of these, you're more likely to find yourself doubly pregnant. Even if you have absolutely none of these, there's still a chance. If you're a year-old Norwegian fertile turtle and an only child from a line of only children, you still have a chance of conceiving fraternal twins , noted Stanford University.
As for having identical twins? You can have a medication abortion up to nine weeks of pregnancy. You can have a surgical abortion from around six weeks of pregnancy onwards. Age affects the fertility of both men and women, and is the single biggest factor affecting a woman? Androgen deficiency in women and its treatment is controversial, and more research is needed. IVF in-vitro-fertilization and ICSI intracytoplasmic sperm injection are assisted reproductive treatment ART procedures in which fertilisation of an egg occurs outside the body.
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On this page. Multiple births are more common than they were in the past, due to the advancing average age of mothers and the associated rise in assisted reproductive techniques, in particular the use of fertility drugs. Twins account for over 90 per cent of multiple births. There are two types of twins — identical monozygotic and fraternal dizygotic. To form identical twins, one fertilised egg ovum splits and develops two babies with exactly the same genetic information.
This differs from fraternal twins, where two eggs ova are fertilised by two sperm and produce two genetically unique children, who are no more alike than individual siblings born at different times. Twins are more or less equally likely to be female or male. It's possible, though, that if Dad inherited the gene for hyperovulation, he could pass that gene onto daughters, increasing their chances of twinning — and yours of having twin grandchildren.
Think you might be having twins? A first trimester ultrasound will confirm that you are, but there are some early signs of a twin pregnancy that might make you wonder. Read our article on signs you're having twins or multiples to find out more.
BabyCenter's editorial team is committed to providing the most helpful and trustworthy pregnancy and parenting information in the world. When creating and updating content, we rely on credible sources: respected health organizations, professional groups of doctors and other experts, and published studies in peer-reviewed journals.
We believe you should always know the source of the information you're seeing. Learn more about our editorial and medical review policies. Hoekstra C et al. Dizygotic twinning. Human Reproduction Update 14 1 Machin G. Non-identical monozygotic twins, intermediate twin types, zygosity testing, and the non-random nature of monozygotic twinning: A review. Martin J et al. National Vital Statistic Reports 70 2.
Births: Final Data for See table Centers for Disease Control and Prevention. Mbarek H et al. Identification of common genetic variants influencing spontaneous dizygotic twinning and female fertility.
The American Journal of Human Genetics 5;98 5 Is the probability of having twins determined by genetics? Fraternal twins. National Human Genome Research Institute.
Identical twins.
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