Twins, Triplets: types, how they are formed, Risks!

A woman can be pregnant and give birth to more than one child. Two is a twin, three are triplets, four is quadruplets, and so on. Isn’t it beautiful that a woman can give birth to so many children at a time?
Even as much as 7. This is known as Multiple gestation.

Today, we are going to explain how this happen, the types of twins, the chances of you having twin as well as the risk that come with being pregnant with more than one baby, so you can take precaution early on.

How Twins, Triplets are Formed

Twins can be formed in two ways.

  • Either from two different eggs that was released at the same time and both fertilized, or
  • from a single egg that was fertilized and then split into two.

Types of Twins

Hence, with this different ways of formation, there here are two main types of twins.

Monozygotic Twins

This is the one we know as the IDENTICAL TWINS. In this type, the woman ovulates ONE EGG which is joined by ONE SPERM & becomes ONE ZYGOTE. This now divides as it progress into 2 babies, so they share the same component hence they are identical, like a photocopy of each other.
This type of twins are usually so similar you can barely tell them apart
They are always of the gender. Either both are males or females. They can have the same placenta.

An Identical twin. the same Sex.

During the past in some places in Nigeria, the people do not understand how this happens, and they think its an abomination to have one person in two places, and hence, they kill them both until the coming of Mary Slessor, a scottish missionary, who stopped the killing of twins.

Dizygotic twins

This are the ones you call NON-IDENTICAL or FRATERNAL TWINS. In this case, the woman releases TWO different EGGS during ovulation & these eggs are joined by TWO DIFFERENT SPERMS to become TWO different ZYGOTES & make 2 different babies.
These ones do not look identical just like the normal siblings, and they can be of the same/different gender. Either male & female or same.
This is the more common type. About 70% of twins are non identical.

Conjoined twins

This type are usually joined together either at the head, body or limbs. They share a particular part of the body together. What happens in conjoined twins is that, they were supposed to be identical twins, but the division of the one zygote that was formed from one sperm & one egg now happened late (after day 13).

Cojoined Twins. Image credits: BBC

Triplets, Quadruplets

These are all formed the same way like that of the twins. Only in this case, more than one or two eggs are released by the woman and they are all fertilized, leading to the development & birth of these number of children.

Care of Women with Twin & Higher Pregnancies

Every woman who is pregnant is advised to start antenatal care as soon as they confirmed they were pregnant, so that ultrasound scan and other examination would be done to access the lady and prepare for her delivery ahead of time, especially if she is having more than one baby.

They would need more care and concern because they are a high risk pregnancy.

Risk of Twin Pregnancy

Women with twin pregnancies require two times the care that normal pregnancies have.
This is because, they are at more risk of all the complications of pregnancy like; nausea, vomiting, heartburn, hypertension, diabetes etc

As well as serious pregnancy complications like; Pre-Eclampsia, Ecclampsia, bleeding in pregnancy, increased perinatal deaths, growth restriction of the child, Twin-Twin transfusion syndromes (TTSS), preterm labour, etc.

Hence, the need for early & effective antenatal care.


  • Dr Abosede Lewu is a specialist Obstetrician and Gynaecologist. She is an Expert on Women's Health, (Fibroids, Infertility, Menstruation & Pregnancy issues). Dr. Abosede Lewu holds an MBBS Degree from the University of Maiduguri, Borno State Nigeria. You can follow Dr. Lewu on twitter: @NaijaObgyn for all Obstetrics and Gynaecology related complaints.

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