Lead investigator Dongmu Zhang of Global Health Outcomes, Merck & Co. and colleagues analyzed and compared the cost of multiple versus single-birth pregnancies.
For mothers, the cost included medical expenses during the 27 weeks before and up to 30 days after the delivery date. For infants, costs contained all medical expenses up to their first birthday.
The researchers compared costs associated with multiple pregnancies versus singletons in the United States, using the Truven Health MarketScan Commercial Claims and Encounters Database.
The study population included all women ages 19-45, who delivered at least one live born infant between January 2005 and September 2010.
The study, published in the American Journal of Obstetrics & Gynecology, found 437,924 eligible delivery events during the study period and about 97 percent were single infants, 2.85 percent were twins and 0.13 percent were triplets or more.
"On average, combined all-cause healthcare expenses for mothers with twins or higher-order multiple births were about five and 20 times more expensive, respectively, than singleton delivery," Zhang said in a statement.
"The greater expenses were likely to have been due to increased maternal morbidities -- hypertension, cardiovascular disease, diabetes, edema/renal disease, genitourinary infection, thyroid disease and anemia -- significantly increased use of Caesarean section and longer hospital stay for the deliveries in women with multiple pregnancies, and increased admission and longer stay in a neonatal intensive care unit for newborns of multiple births."
There was also an increased mortality for both mothers and infants associated with multiple pregnancies, although the absolute rates were small, Zhang added.