Women who wait to have their first child beyond the standard cut-off age of 35 have an increasingly better chance of giving birth to a healthy baby, new research has discovered.

They can look forward to a live-birth rate of 994 in 1,000, provided they have been screened early enough for anomalies in the growth of the fetus, researchers conclude.

Researchers from Harvard Medical School have found that the dangers of having a stillbirth have dropped dramatically since the 1960s, even though the average maternal age has risen from 27 to 30 years. The fetal death rate in the 1960s was around 11.5 per 1,000 births compared to just 3.2 per 1,000 today.

Although the over-35s face a significantly higher rate of fetal death compared to younger mothers, this still equates to a six per 1,000 births risk of fetal death, while younger mothers had a risk of just half that.

However, older first-time mothers also face a series of complications up to the time of birth, ranging from spontaneous abortion, fetal anomaly, preterm delivery, fetal growth retardation and stillbirth. Other research shows that these risks increase fourfold as the woman passes 35. Fetal malformations occur in 1 in 50 women around the age of 40. Widespread screening has lowered the numbers of malformed fetuses being delivered, the researchers believe.

Researchers based their findings on the McGill Obstetrical Neonatal Data base, which assessed risks from deliveries carried out at the Royal Victoria Hospital in Montreal from 1961 to 1993 (New Eng J Med, October 12, 1995).