Risks of Multiple Pregnancy

The greatest risk to undergoing fertility treatment is multiple pregnancy. Most fertility treatments will increase your risk for multiple pregnancy. Complications increase with each additional fetus in a multiple pregnancy and include severe nausea and vomiting, Cesarean section, or forceps delivery. You should be aware of these and other potential problems you might experience.

Premature Birth

Premature labor and delivery pose the greatest risk to a multiple pregnancy. Feasibility of a vaginal delivery depends on the size, position, and health of the infants, as well as the size and shape of the pelvic bones. Cesarean section is often needed for twin pregnancies and is expected for delivery of triplets. Although only 1% of all deliveries are twins, they account for 10% of all premature deliveries. Compared to singletons, of which eight per 1,000 die in the first month of life, twins are seven times more likely to die (56 deaths per 1,000), and triplets are 20 times more likely to die (160 deaths per 1,000).

Since premature labor and delivery present such a serious risk, a woman contemplating fertility treatment must understand the risks associated with prematurity that occur with multiple pregnancies.

Placental Problems

The placenta is attached to the wall of the uterus, and the fetus is attached to the placenta by the umbilical cord. The placenta provides blood, oxygen, and nutrition to the fetus through the umbilical cord. Placental function is likely to be abnormal in a multiple pregnancy. The placenta ages prematurely and may slow fetal growth, especially late in the third trimester. If the placenta is unable to provide adequate oxygen or nutrients to the fetus, the fetus cannot grow properly. This is known as intrauterine growth restriction or IUGR.

IUGR occurs when a fetus has a weight is below the 10th percentile for its gestational age and whose abdominal circumference is below the 2.5th percentile. For a full term delivery, the cutoff birth weight for IUGR is 2,500 g (5 lb, 8 oz). Infants who weigh less than 2,500 g (5 lb, 8 oz) at term have a perinatal mortality rate that is five to 30 times greater than that of infants whose birth weights are at the 50th percentile. The mortality rate is 70 to 100 times higher in infants who weigh less than 1,500 g (3 lb, 5 oz). Low birth weight of less than 5 and a half pounds (2,500 grams) occurs in 50% of twins. The average birth weight is approximately 4 pounds (1,800 grams).

Another placental problem is twin-twin transfusion, a life threatening condition in identical twins. This transfusion occurs when blood flows from one fetus to the other. Poor growth occurs in the “donor” twin, and excessive blood passes to the “recipient” twin. Therapeutic amniocentesis and laser coagulation of blood vessels may reduce complications of twin-twin transfusion.


Preeclampsia, also known as toxemia, occurs three to five times more often in multiple pregnancies. Preeclampsia is diagnosed when the mother’s blood pressure becomes elevated and protein is detected in the urine. The condition may progress and threaten the health of the mother and the pregnancy. When severe, the mother may have seizures or even a stroke.


Women with multiple pregnancies are more likely to develop gestational diabetes which is diabetes (elevated blood sugar) occurring during pregnancy. Mild gestational diabetes can cause problems for the baby including macrosomia (excess growth which causes the baby to be at increased risk for birth injuries or cesarean section). Babies at are greater risk for respiratory distress after birth, diabetes, obesity and developmental problems later in life. Women with gestational diabetes are also more prone to diabetes after pregnancy. 

Fetal and Newborn Complications

Premature delivery places an infant at increased risk for severe complications or early death. A baby’s lungs, brain, circulatory system, intestinal system, and eyes may be too immature. These severe problems will often require that the babies stay in an intensive care unit specially designed for very ill babies. This is known as the neonatal intensive care unit or NICU. Survivors of premature birth may have lifelong handicaps.

Of the premature babies who die, 50% succumb to respiratory distress syndrome, the inability to circulate oxygen from the lungs throughout the body. Brain damage is responsible for almost 10% of premature newborn deaths. Birth defects and stillbirths account for about 30% of the deaths in twins and multiple pregnancies.

Cerebral palsy

Cerebral palsy is condition, sometimes thought of as a group of disorders that can involve brain and nervous system functions such as movement, learning, hearing, seeing, and thinking. Cerebral palsy is more common in twins than singletons. Among twins, if one twin suffers a fetal death or dies in infancy, the prevalence of cerebral palsy in the surviving co-twin is considerably increased, and those that are the same sex are particularly at high risk.