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Multiple Pregnancy

The presence of more than one foetus in the uterus increases the likelihood of birth defects as well as problems during labour and delivery. Multiple births refers to both twins or higher order multiples (triplets or more).

1. Twins . Twins means that there are 2 foetuses in the uterus . Twins are either fraternal (not identical as 2 separate eggs are released and fertilised ; 70% of twins) or identical (both foetuses come from the division of a single fertilised ovum ; 30%). While fraternal twins have separate placentas , identical twins may share a placenta, although not always. When twins share the same sac , they are called monoamniotic , while twins that share the same placenta they are called monochorionic . Identical twins are always of the same sex or gender, while fraternal twins may be either the same sex or opposite sex.
Twins are relatively frequent in occurrence with about 1 in every 70 to 80 pregnancies bearing twins. The presence of twins is usually detected before delivery, with an ultrasound examination or foetal electronic monitoring that shows two distinct heartbeats.

All mothers expecting twins are at increased risk for the following:

2. Higher Order Multiples (Triplets Or Greater). The incidence of higher order multiple pregnancy is greater with advances in infertility treatment, with up to 30% of patients who use assisted reproductive technology conceiving twins or higher order multiple pregnancies. Such pregnancies entail risks both for mother and foetuses:

  • Risks for the Foetuses.
    1. The risks of preterm birth, death of a baby in the uterus, neonatal death and slow growth of a baby in the uterus are greater in a multiple pregnancy than twins or the case of a single foetus.
    2. The average gestational age for delivery of twins is 35 weeks, triplets is 33 weeks and quadruplets is 31 weeks. Thus the risks associated with prematurity are much greater in higher order pregnancies.
    3. There is a higher chance that a multiple pregnancy will have one or more foetus with a birth defect or a chromosome problem.
    4. This all implies poorer outcome for multiple pregnancies than both twins and single foetuses.
  • Risks for the Mother .
    1. Up to 98% of mothers expecting triplets will experience some complication during the pregnancy.
    2. The risks of preterm labour , premature rupture of membranes , preeclampsia , gestational diabetes , anaemia , and a serious pregnancy liver problem ( acute fatty liver of pregnancy ) are all increased in a higher order multiple pregnancy.
    3. A caesarean section will most often be needed.
    4. Complications during and after childbirth such as haemorrhage , infection and hospital readmission are also increased.

For further, more detailed information on this topic, please refer to the reference source for this page.

The information in this page is presented in summarised form and has been taken from the following source(s):
1. Dartmouth Hitchcock Medical Center, Division of Maternal Fetal Medicine & Prenatal Diagnosis:

Other HON resources 
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Multiple Pregnancy
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Contact Last modified: Jun 25 2002