Early births linked to fertility problems

Couples with fertility problems are more likely to have premature babies, low birth weight babies and a Caesarean birth, according to a new study based on a registry of 56,000 births. The increased risks apply to couples who eventually conceive naturally, as well as those who undergo fertility treatment. The authors, who published their findings in the journal Human Reproduction, say that doctors need to be aware of these risks when caring for pregnant women who had difficulty conceiving.

Olga Basso of the University of Aarhus in Denmark and Donna Baird of the US National Institutes of Health looked at information on 55,906 single births recorded in the Danish National Birth Cohort. They found that 15 per cent of first-time mothers, and eight per cent of women having subsequent babies took over a year to conceive. Around half of this group eventually fell pregnant naturally, while the rest underwent fertility treatment. But compared to women who conceived naturally in less than a year, all these 'infertile' women had a higher risk of having a pre-term baby (born before 37 weeks of pregnancy), a full-term baby with a low birth weight, and a Caesarian operation. 'The increased risk of pre-term birth is of most concern' said Basso. 'It was nearly 40 per cent higher for first-time mothers and nearly 80 per cent higher for women having their second or subsequent baby'. She said that there had been a controversy about the potential adverse effects of fertility treatment on birth problems, but limited evidence about women who have fertility problems but conceive without treatment. 'One study in 1997 showed that women who conceived naturally after a long time were at higher risk of pre-term birth. Our study confirms that with a much larger sample' she added.

Dr Basso said that further research was needed, to pin down the differences between fertile and infertile couples that might contribute to birth problems. The authors also say that the fact that treated and untreated infertile first-time mothers had similar risks provided some reassurance that fertility treatments themselves 'may not be a major factor in adverse birth outcomes'. But they point out that the underlying causes of infertility are likely to differ between treated and untreated women, so the effect of treatment is still uncertain. Peter Bowen-Simpkins, a spokesman for the UK's Royal College of Obstetricians and Gynaecologists, welcomed the new research: 'These statistics are pretty staggering' he said. 'Anyone who takes a long time to conceive must be considered to be in a higher risk group in the same way as women over 35 who give birth are regarded medically as 'special'.