What type of twin are there

In this case, both fertilized eggs will develop, but one twin will be slightly older than the other. This is known as heteropaternal superfecundation — a common occurrence in animals but very rare in people. Twin pregnancies often come with an increased risk of developing some medical conditions.

These can include:. A twin pregnancy has risks of complications, so parents should make sure to receive good prenatal care and seek medical attention for any concerns. Identical twins are the same in so many ways, but does that include having the same fingerprints?

There's conflicting information out there so we look…. The chances of having twins are certainly higher than they were 20 years ago, but why? We'll tell you what's changed and what you may be able to do to….

Do twins run in families? Can twins skip a generation? Learn more about how twin pregnancies happen and all about your chances of having a twin…. Learn how twin types are defined, including the affect of fraternal or identical twins and risks of a…. Identical, fraternal, and What are mirror twins? Learn more about characteristics and identification of mirror twins.

A new study finds that epidurals do not affect child development in their later years. A fetal arrhythmia is an irregular heart rate — too fast, too slow, or otherwise outside the norm.

It's often benign. Postpartum diarrhea after a C-section is normal. Health Conditions Discover Plan Connect. Identical Nonidentical Third type Unique identical twins Unique fraternal twins Risks Takeaway You may be familiar with the most common types of twins — fraternal and identical — but several other rare subtypes exist too.

Identical twins. Nonidentical twins. Is there a third type? Unique identical twins. Unique fraternal twins. Medical risks during a twin pregnancy. The takeaway. Parenthood Pregnancy. Do Twins Skip a Generation? What Are Mirror Twins? Basically, fraternal twins are as alike as siblings would be — in other words, they are not identical. Fraternal twins might be two boys, two girls, or a boy and a girl. Each baby develops in his or her own placenta. Identical twins, or monozygotic twins, form when one fertilized egg splits in two and grows into two separate embryos.

The twins are the same gender, share the same blood type, and share the same physical traits. Identical twins may or may not share one amniotic sac.

This is how each twin evolves to be a unique individual. In some rare cases, the embryo only partially separates, and the two fetuses remain partially connected as they grow. Conjoined twins can connect at different spots, including the chest, abdomen, or hips. The twins may also share one or more internal organs. Assisted reproductive techniques — many procedures rely on stimulating the ovaries with fertility drugs to produce eggs and, often, several eggs are released per ovulation.

Fertilisation Hormones secreted by the ovaries, and a small gland in the brain called the pituitary, control the menstrual cycle. The average cycle is around 28 days. After a menstrual period, rising levels of the hormone oestrogen help to thicken the lining of the womb the endometrium and release an egg from one of the ovaries ovulation. If the egg is fertilised on its journey down the fallopian tube, it lodges in the thickened womb lining, starts dividing and evolves into an embryo.

This occurs because the fertilised egg divides in two while it is still a tiny collection of cells. The self-contained halves then develop into two babies, with exactly the same genetic information.

The biological mechanisms that prompt the single fertilised egg to split in two remain a mystery. Approximately one quarter of identical twins are mirror images of each other, which means the right side of one child matches the left side of their twin. These babies will be no more alike than siblings born at separate times.

The babies can be either the same sex or different sexes, with the odds roughly equal for each. It is proposed that the egg splits in two, and each half is then fertilised by a different sperm. This theory is an attempt to explain why some fraternal twins look identical.

Gestation for twins The normal length of gestation for a single baby is around 40 weeks. However, gestation for twins, either identical or fraternal, is usually around 38 weeks.

Since twins are usually premature, they are more likely to have lower birth weights. Prematurity is associated with increased risk of a number of disorders, including jaundice. Giving birth to twins Childbirth can give rise to complications when just one baby is present, so twins present extra potential for difficulties. It is advised that women carrying twins give birth in hospital, rather than at home. The babies can be delivered vaginally, but caesarean section delivery may be considered a better alternative in some circumstances.

Zygosity testing It is difficult to tell if twins are identical or fraternal at birth. Some identical twins may be born with individual sets of membranes, which may lead to the mistaken assumption that the babies are fraternal.