Having twins as a results of in vitro fertilization (IVF) carries higher risks of complications for both mother and babies than having two single babies from separate IVF procedures, according to a Swedish study.
The extra concerns that come with multiple births are nothing new. But even as many fertility clinics have stopped regularly transferring more than one embryo, debate has continued over whether having twins through IVF is really a bad thing for couples desperate for children.
"The neonatal and maternal outcomes were dramatically better for women undergoing two IVF singleton pregnancies compared with one IVF twin pregnancy after double-embryo transfer," wrote lead researcher Antonina Sazonova in the journal Fertility and Sterility.
"These results support single-embryo transfer to minimize the risks associated with twin pregnancies," added Sazonova of Sahlgrenska University Hospital in Gothenburg, Sweden.
The researchers analyzed data from fresh and frozen embryo transfers done at Swedish IVF clinics between 2002 and 2006. Those records included 991 women who ultimately gave birth to twins after a double embryo transfer and 921 mothers with two children born through separate rounds of IVF.
Almost 47 percent of twin babies were born prematurely and 39 percent were considered low birth weight, the team reported. That compared to the seven percent of singleton babies that were preemies and less than five percent born small.
Twins were also more likely to have breathing complications, sepsis or jaundice. Their mothers had two to three times more preeclampsia—high blood pressure and protein in the urine—and were four times more likely to need a C-section than women who had two single births.
However, there was no difference in the babies' chances of having severe malformations and other life-threatening health problems.
"A lot of patients, when they've had infertility for a long time, think that it's a bonus to get two," said Lynn Westphal, a women's health and fertility specialist at Stanford University Medical Center in Palo Alto, California.
"We know it's always safest to have one child at a time," added Westphal, who wasn't involved in the new study, adding that she and her colleagues have been counseling more and more women to have a single embryo transferred, especially the younger and healthier patients.
Some data suggest women are just as likely to get pregnant if they have a single embryo transfer, versus more than one. But the findings have been inconsistent, Westphal said.
"A lot of patients are focusing just on getting pregnant, they're not looking at the whole pregnancy and looking at the outcome of twins," she said.
"They're just thinking if they transfer more, they're more likely to get pregnant. And they're thinking if they have twins, they're just getting everything done at one time." —Reuters