Multiple pregnancies, when there is more than one baby, always need special care and monitoring.
Identical twins occur when one fertilised egg splits into two. These babies are always the same sex and share a placenta. All of us have a one in 250 chance of having identical twins. A history of twins in the family increases the chances.
Fraternal twins occur when two eggs are fertilised by two different sperm. They have two different placentas, although sometimes these fuse together during pregnancy. A history of twins on the mother’s side makes fraternal twins more likely.
Triplets, quads, quins and sextuplets can occur spontaneously and are usually fraternal although identical triplets are possible.
These days most cases of multiple births occur because of fertility treatment when drugs are used to stimulate the ovaries into producing more eggs. IVF can also result in a multiple pregnancy because more than one fertilised embryo is put back into the mother to improve the odds of one surviving.
A mother must take extra precautions during multiple pregnancy because there is an increased risk of the babies being born prematurely or having low birth weights.
In general the more babies, the more premature the birth is likely to be, so medical staff will take extra precautions when dealing with women expecting triplets or more.
Twins are usually smaller than single babies with one twin often smaller and weaker than the other. The difference can sometimes be so great that one twin needs intensive care while the other is fine. This difference in size usually evens out eventually, but sometimes not until adulthood.
Other precautions during a multiple pregnancy include monitoring the babies’ blood supply. Blood sometimes crosses the placenta to pass between the babies with one becoming anaemic (too few red blood cells) and very pale, while the other is polycythaemic (too many red blood cells) and a dark red colour. This, treatable condition, is another reason why women having a multiple pregnancy must have regular pre-natal checkups and must heed medical advice if told they would be better off under supervision in hospital.
A mum carrying more than one baby must also rest more. If contractions do start too early then doctors can administer relaxing drugs to the womb to give the babies more time to develop.
Usually a woman carrying three or more babies will automatically be admitted to spend the last few weeks in hospital, but this can depend on her circumstances and general health.
Multiple births are more likely to be delivered by caesarean section. But there is no reason why twins should not be delivered vaginally providing both their heads are in the down position.
A mother delivering twins or more will be at greater risk of haemorrhage, but the medical staff will be aware of this danger and will take all the necessary precautions to deal with it.