Their study challenges a myth that prevails among birth attendants that strong pelvic floor muscles (for example, as a result of horse riding) may obstruct labour.
They identified 301 healthy pregnant women who had not given birth before. Half the women took part in an intensive pelvic floor muscle training programme between the 20th and 36th week of pregnancy. The other half acted as a control group.
Duration of the second stage of labour (active pushing time) and number of prolonged deliveries (more than 60 minutes of active pushing) were recorded.
Women in the training group had a lower rate of prolonged second stage labour than women in the control group, with 24% undelivered after 60 minutes of active pushing compared to 38% in the control group.
However, there was no significant difference in the duration of the second stage of labour between groups (40 minutes versus 45 minutes).
Despite the borderline significance of the results, intensive training of the pelvic floor muscles during pregnancy results in improved muscle control and strong flexible muscles, and seems to facilitate rather than obstruct labour, conclude the authors.