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Multiple Gestation

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Most of the risks to infants resulting from multiple gestation pregnancies are due to the increased likelihood of premature delivery. The more babies who result from a pregnancy, the greater the likelihood of premature delivery.

The average length of multiple gestational pregnancy is as follows

  •  Single baby: 40 weeks
  • Twins: 36 weeks
  • Triplets: 32 weeks
  • Quadruplets: 28 weeks

Each additional baby in the uterus shortens the pregnancy by about 4 weeks on average. The survival and outcomes of premature infants are improving year by year as a result of new developments in high-risk obstetrics and newborn intensive care. However, significant risks remain, particularly for infants born very early in pregnancy (before 30 weeks).


If quadruplets are born before 24 weeks, it is likely that all will die. Even at 24 weeks, there is only about a 13% chance that all four infants will live. At 28 weeks, the chance for each infant is about 95%; so statistically, the chance of that all four will live is about 81% (.95 x .95 x .95 x .95).


If triplets are born at the average time in pregnancy, 32 weeks, the survival chance for each infant is about 98%. The chance that all three will live is about 94% (.98 x .98 x .98). In real life, due to other problems separate from prematurity, the survival risk is likely to be much lower.
These complex probabilities can be summarized in a table as shown below.

24 Weeks

Single Twins Triplets Quads
Survival of each baby 60% 60% 60% 60%
Survival of all babies 60% 36% 22% 13%

28 Weeks

Single Twins Triplets Quads
Survival of each baby 95% 95% 95% 95%
Survival of all babies 95% 90% 86% 81%

32 Weeks

Single Twins Triplets Quads
Survival of each baby 98% 98% 98% 98%
Survival of all babies 98% 96% 94% 92%

36 Weeks

Single Twins Triplets Quads
Survival of each baby 99% 99% 99%
Survival of all babies 99% 98% 97%

As the number of babies in a pregnancy increases, the length of pregnancy needed for survival of all babies increases, but the expected pregnancy length decreases.

Single Twins Triplets Quads
Weeks of pregnancy needed to reach 90% survival of all babies 27 28 30 32
Average length of pregnancy 40 36 32

Length of Hospital Stay

The total hospital costs for the care of the babies depends on two factors: the number of babies and the length of hospitalization. The average hospital stay is about 3 months for babies born at 24 weeks and 2 months at 28 weeks, 1 month at 32 weeks and 1 week at 36 weeks. Thus the expected total number of hospital days for all babies would be as follows:

Single baby: 2 days x 1 = 2
Twins: 7 days x 2 = 14
Triplets: 30 days x 3 = 90
Quadruplets: 90 days x 4 = 360

These estimates depend on the assumption that a pregnancy will be of average length. It is often possible, with careful obstetrical management for the pregnancy to be prolonged past the average length. Excellent health care insurance is obviously important for families with multiple-gestation pregnancies. It is important to be certain that your insurance will cover neonatal intensive care in a Level 3 or Comprehensive Center, such as the University of North Carolina.

Multiple gestations often require extended periods of bed rest for the mother at home or in the hospital. Exact figures are not available for these periods of time.


Another important consideration is the risk of complications of prematurity. The risk increases with shorter pregnancies. The most important complications of prematurity are summarized.
Lung problems

The most common problem confronting premature infants is immaturity of their lungs. This problem often requires special treatment and may occasionally cause long-term problems in survivors; it may also delay the recovery of some premature babies, especially those born before 28 weeks.
Bleeding complications

One of the most serious potential complications of prematurity is spontaneous bleeding in the brain. This occurs in 10 to 20% of babies born before 32 weeks. A chance of hemorrhage of any severity in infants <32 weeks is 20%, and the chance of severe brain hemorrhage is 11%. The risk is higher in the earliest babies. Many of these hemorrhages are small and cause no long-term effects, but more severe bleeding episodes may be associated with permanent impairment of brain function. Bleeding in the lungs is another serious potential complication in very early premature babies.


Necrotizing enterocolitis is a complication of prematurity resulting in nonviable portions of the intestines. This may result in sepsis of the infant, often requiring bowel segmental resection.

Eye problems

Infants born very prematurely (before 28 weeks) may have abnormal growth of blood vessels on the retina, the back of the eye. This is a common complication that usually goes away spontaneously. In severe cases, the problem, if untreated, may progress to retinal detachment and blindness. Premature infants are also at increased risk of other eye problems such as nearsightedness and eye muscle problems. It is quite common for premature infants to require glasses later in childhood because of one or more of these problems.

This information is provided to assist you in evaluating the risks to infants resulting from multiple gestation pregnancies. The figures presented here are inexact and likely to change with time and improving obstetrical and pediatric therapy. If you would like to discuss any of these issues further, please ask your physician or nurse to arrange for a neonatology consultation with your hospital. Figures for survival are slightly higher in the USA.