The duration of a normal singleton pregnancy ranges from 37 weeks to 42 weeks from the time of the last menstrual period.
Twin pregnancies occasionally progress to 40 weeks but almost always deliver early. As the number of fetuses increases, the expected duration of the pregnancy decreases. The average duration is 35 weeks for twins, 33 weeks for triplets, and 29 weeks for quadruplets.
Pregnancy Type Average Gestational Age at Delivery Average Birth
Singleton 40 weeks 7 lbs (3300 gms)
Twins 35 weeks 5.5 lbs (2500 gms)
Triplets 33 weeks 4 lbs (1800 gms)
Quadruplets 29 weeks 3 lbs (1400 gms)
CARRYING A MULTIPLE PREGNANCY
In order to achieve the best outcome with a multiple pregnancy, the expectant mother must work as
part of the health care team. A nearly total change in lifestyle can be expected, especially after about
20 weeks into the pregnancy.Metabolic and Nutritional Considerations
There is an increased need for maternal nutrition in multiple pregnancies. An expectant mother needs
to gain more weight in a multiple pregnancy, especially if she begins the pregnancy underweight. With
multiples, weight gain of approximately 45 pounds is optimal for normal weight women. The pattern of
weight gain is important too. Healthy birth weights are most likely achieved when the mother gains
nearly one pound per week in the first 20 weeks. In addition to weight gain, most physicians
recommend increasing vitamin supplementation by 50% to 100%. The increase in fetal growth with
appropriate nutrition and weight gain may greatly improve pregnancy outcome at a minimum of cost.
Many physicians who manage multiple pregnancies believe that a reduction in activities and
increased bed rest prolongs these pregnancies and improves outcomes. Women with multiple
pregnancies are usually advised to avoid strenuous activity and employment at some time between
20 and 24 weeks. Bed rest improves uterine blood flow and may increase birth weight up to 20%.
Intercourse is generally discouraged when bed rest is recommended.
Monitoring a Multiple Pregnancy
Since preterm birth and growth disturbances are the major contributors to newborn death and
disability in multiples, frequent obstetric visits and close monitoring of the pregnancy is needed.
Prenatal diagnosis by chorionic villus sampling and amniocentesis may still be performed to screen
for Down syndrome and other genetic abnormalities. These procedures are complicated and difficult
to perform in twins and triplets, and may not be possible in high order multiple pregnancies.
Many physicians perform cervical examinations every week or two beginning early in pregnancy to
determine if the cervix is thinning or opening prematurely. If an exam or ultrasound shows that the
cervix is thinning or beginning to dilate prematurely, a cerclage, or suture placed in the cervix, may
prevent or delay premature dilatation. Tocolytic agents are medications that may slow or stop
premature labor. These medications are given in hospital “emergency” settings in an attempt to stop
premature labor. It is important to attempt to delay delivery to minimize the risks of premature delivery.
Ultrasound examinations in the second trimester can identify some birth defects. Assessment of fetal
growth by ultrasound every three to four weeks during the second half of pregnancy is commonly
performed. Every multiple pregnancy should be considered “high risk,” and obstetricians experienced
with the management of multiple gestations should provide care. A neonatal intensive care unit
nursery should be available to provide immediate and comprehensive support to premature
Vaginal delivery of twins may be safe in some circumstances. Many twins can be delivered vaginally if
the presenting infant is in the head first position. Most triplets will be delivered by Cesarean section.
Appropriate anesthesia and neonatal support are essential, whether delivery is performed vaginally or
requires Cesarean section. Delivery of multiples requires planning by the entire medical team and
availability of full intensive care support following birth.
Psychosocial Effects of Multiples on a Family
Although many women with a multiple pregnancy do well, their families may experience significant
stress. If prolonged hospitalization is needed, arrangements must be made for work, home, and family
care. Even if medical problems are overcome and the infants survive without disability, the effect of
multiple births on family life is profound and life-altering. The impact of a multiple birth clearly affects
the parents, but also the babies, other siblings, and the extended family. Financial stresses may be
overwhelming. Obvious additional costs include feeding, clothing, housing, and caring for multiple
Psychological counseling and support groups may provide a lifeline for the parents of multiples, who
may feel isolated or depressed. Most physicians can provide appropriate referrals to a mental health
professional or a support group.CONCLUSION
The objective of infertility treatment is the birth of a healthy child. In a small percentage of patients,
treatment results in multiple pregnancies that may place the mother and the babies at increased risk
for an unhealthy outcome. Since multiple pregnancies and their complications are an inevitable risk of
fertility therapies, education about these risks is crucial prior to treatment. Ultimately, prevention is the
key to reducing the risk of multiple pregnancies.