Mar 2 2010
Whether a women gets pregnant the "traditional" way or by assisted reproduction has no effect on the birthing process itself or the baby, researchers at the Norwegian University of Science and Technology (NTNU) have found.
Gynaecologist and medical researcher Liv Bente Romundstad and colleagues from NTNU and St Olav's University Hospital in Trondheim looked at the pregnancies of more than 1.2 million Norwegian women whose births were listed in the Medical Birth Registry of Norway between 1984 and 2006. Of these, 8229 were pregnancies that resulted from assisted reproduction technology.
In a series of articles published in The Lancet and Human Reproduction, the researchers reported finding no difference between infants of women who had conceived spontaneously and after assisted fertilization in birth weight, gestational age, risks of being small for gestational age, and preterm delivery. Researchers found a higher risk of breech births in pregnancies from assisted fertilization, but their findings suggest the difference is due not to the technology itself, but to the gestational age of the baby and the number of previous deliveries that the mother had had.
Breech births
Romundstad found that five percent of the children from assisted reproduction are born in a breech presentation, compared with three percent of the average. She says this has a straightforward explanation: Mothers who have children by assisted reproduction, are in fact slightly older than average, tend to have shorter pregnancies, and fewer previous births.
When Romundstad adjusted for these differences, she found out that the difference in the proportion of breech births disappeared completely.
"We also believe that some of the frequency of breech births can be explained by the fact that children often are in the breech position early in the pregnancy," she said. "The children turned several times during the pregnancy, and assumed the head-down position when the normal gestation period ended."
"If a child is born before the end of the gestation period, it is not clear that the child has time to assume the head-down position," Romundstad says.
Greater worries then - but not now
The second important key finding pertains to how the Norwegian health system treated mothers who became pregnant using assisted reproduction.
"We were more anxious earlier. When we first started with assisted reproduction in 1984, all of these mothers were carefully monitored, and the children were born by Caesarean section," Romundstad said. "This is a clear difference from women who didn't need help getting pregnant. For these women, the Caesarean section rate was about 10 per cent."
Now, Romundstad says, the rate of Caesarean sections in the two groups is quite similar. "For children in the breech position, the difference completely gone," she says.
No reason for concern
Romundstad says the bottom line is that assisted reproduction itself doesn't have an adverse affect on pregnancies or babies' outcomes. There may be conditions that differ in mothers who use reproductive technologies compared to mothers who don't need help getting pregnant, but those conditions are not due to the technology itself, she says.
"We want to avoid unnecessary medical intervention," Romundstad says. "If there are no other medical indications, there is no reason to handle mothers who have used assisted reproduction differently than other mothers of the same age who have had the same number of births."
Survival rates the same
Norway has a unique database for studying birth outcomes. The Medical Birth Registry in Bergen contains data for all Norwegian births from 1967. Beginning in 1984, records were also kept for "test tube" babies. Mothers who use assisted reproduction are given an ultrasound early in their pregnancies, and are followed until the child is one week old.
Romundstad has used these data to also show that the risk of mortality is the same for test tube children as for other children.
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