Maternal height as a risk factor for Caesarean section due to failure to progress in labour.

We examined for a regional sample of the New Zealand population, the relationship between maternal height and an increased risk of emergency Caesarean section due to arrested labour, to identify a height below which the risk of Caesarean section increases markedly and to quantify the risk of a Caesarean section for a range of maternal heights. The data of nulliparous singleton pregnancies over the period 1994-1998 was sorted into 2 study groups, one resulting in emergency Caesarean section for arrested labour and the other a group of women who had normal vaginal delivery requiring no intervention. The means and standard deviations of these 2 groups were found and 99% confidence intervals calculated. They were analysed for statistical difference and then a logistical regression calculation tried to identify a height at which the risk of a Caesarean section increased suddenly. There were 81 women in the Caesarean section group and 997 in the normal vaginal delivery group. Mean heights and confidence intervals were 161.0 cm (158.9-163.1) and 164.6 cm (164.0-165.2) respectively. There was a statistically significant difference between these means (p<0.001) but logistic regression analysis showed that risk of Caesarean section increased gradually with decreasing height, and even then did not reach more than 30% risk until a height of less than 140 cm. Low maternal height was associated with increased risk of Caesarean section due to labour arrest. Because the likelihood of having a normal vaginal delivery was still very good (>80 %) at modest degrees of short stature, this risk factor alone is unlikely to affect management. However the combination of other risk factors with maternal height may be of clinical use.