There was absence of any regional differences in parity progressions and length of birth intervals, although urban-rural differences persisted at most birth orders, suggesting that, as in other studies, the urban-rural differentials are the primary source of variations in fertility between different areas of a country. The significantly higher probability of a subsequent birth after birth order 2 in areas with high infant mortality compared to those with low infant mortality suggests that women in the high-risk provinces may be more likely to advance beyond parity 2 and continue on into the advanced parities. The provinces identified as having high infant mortality had also been identified in other studies as the provinces with the highest crude birth rates and population growth rates, the least available family planning services, and highest crude death rates. Mothers' education was consistently related to the likelihood of another birth at each birth order, with the most-educated women experiencing a significantly lower probability of having a subsequent birth at every birth order. This concurs with results in other studies, suggesting that the woman's education is a prime determinant of fertility and that increasing the educational attainment of women is one of the most beneficial measures to reduce fertility. The significant relationship between the previous birth interval of the index child and the probability that the index child would be followed by a subsequent birth conforms with other studies of birth interval dynamics that suggest that pregnancy-spacing for a given woman remains constant throughout her reproductive career.(ABSTRACT TRUNCATED AT 250 WORDS)