New research shows women's fertility starts declining from late 20s and mens fro...( g of intercourse**. This makes our res...)

From their data the researchers estimated the chances of a woman becoming pregnant following intercourse on a given day relative to ovulation. Assuming intercourse occurred at the peak time for conception (2 days prior to ovulation) and presuming that their partners were the same age, women aged 19-26 had around a 50% chance of pregnancy in any one menstrual cycle. This fell to around 40% for women aged 27 to 34. For women aged 35-39 it was less than 30% if the woman had a partner the same age, but fell further to around 20% if the man was five years older (because his fertility had by then also started to decline).

"Nearly all pregnancies fell within the fertile window and, on average, the day-specific probability of pregnancy declined for women from the late 20s onwards being around twice as high for women aged 19 to 26 as for women aged 35 to 39. When we controlled for the age of women, we found that fertility was significantly reduced for men aged over 35," Dr Dunson said.

He added that it was not surprising to find a decline in female fertility this early as many researchers felt that decline with age during reproductive years was continuous, though gradual.

"Despite this overall trend of declining fertility we found a lot of variation among healthy couples in their fertility. There was enormous heterogeneity that is not accounted for by age. Even focusing on the 50% of couples having closest to average fertility, the range in the probability of pregnancy on the peak day of the fertile window extends from 20% to 60%. Epidemiological studies have identified some of the factors associated with variability, including prenatal exposures, sexually transmitted disease history, smoking and occupational exposures, but much of this heterogeneity remains unexplained."

Dr Dunson said that future research would examine the role of cervical mucus secreti
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Contact: Margaret Willson
m.willson@mwcommunications.org.uk
44-1536-772181
European Society for Human Reproduction and Embryology
29-Apr-2002