A multiple pregnancy or multiple birth is the one in which a pregnant woman carries more than one baby at a single time. There are following type of multiple births:

• Twins for 2 foetuses
• Triplets for 3 foetuses
• Quadruplets for 4 foetuses
• Quintuplets for 5 foetuses
• Sextuplets for 6 foetuses

Multiple pregnancies happen primarily as a result of the following two factors:

• When a fertilised egg splits into two resulting in two embryos before it implants in the uterine lining. This pregnancy is known as identical twinning.
• When two or more eggs are fertilised by different sperms. This type of multiple pregnancy is known as fraternal twinning. 

Multiple births can happen in any pregnant woman. However, some factors increase your chances of having multiple babies. Common factors that may result in multiple pregnancies:

• Being of advanced age (more than 30 years)
• Being a twin or having a twin in your family 
• Taking ART treatment 
• Taking ovulation stimulation drugs

Primarily, an ultrasound exam is needed to know whether or not you have a multiple pregnancy. If you are carrying more than one foetus, you can expect to have double the symptoms. Here are the common signs and symptoms of a multiple pregnancy:

• Severe nausea and vomiting 
• Rapid weight gain in the 1st trimester of pregnancy
• Extremely sore and tender breasts
• High HCG levels 
• High amounts of the protein (alpha-fetoprotein) in your blood

Multiple pregnancies or multiple births require more safety and precaution than a single pregnancy. The risks and complications of a multiple pregnancy are relatively more and include:

• Premature labour and birth
• Preeclampsia 
• Gestational diabetes 
• Placenta abruption 
• Foetal growth restriction