The birth interval, defined as the length of time between two successive live births, indicates the pace of childbearing. It is an important indicator of fertility. Short birth intervals may adversely affect a mother's health and her children's survival. Babies born less than two years after the previous child are at least twice as likely to die in the first year of life as those born after an interval of at least two years. Even if these infants survive the first year, they are 1.5 times more likely to die before age 5 than children whose births were spaced at least 2 years apart (Bohler 1994, Alam 1995, Shane 1997), (Pandey et al.,1998; Govindaswamy et al., 1993). Data from the World Fertility Survey provide a strong evidence about increased mortality risks of children with short birth intervals (Hobcraft et.al, 1985).

Adverse effect of less than optimum birth spacing is also evident in Andhra Pradesh (Figure 1). The infant mortality rate is more than three times as high for children with a previous birth interval of less than 24 months as for children with a previous interval of 48 months or more (NFHS-2). Figure 1 shows the infant mortality rates according to previous birth interval.

Closely spaced pregnancies increase the chances of women having low birth weight babies, and increase risk of transmission of infectious diseases (National Research Council 1989). Rowe and Plomin (1981) argue that within-family influences like birth order and spacing of children, influences on intelligence and make siblings different from one another. Zajonc and Markus (1979) also proposed that children's scores on IQ should be higher in families with wider spacing among siblings. But several studies by different psychologists show that birth order and spacing, show relationships with IQ, but they are not very powerful (Berk, 1989).

According to estimates from the NFHS-2, in 1998-99, the median birth interval in India range for about 27 months in Nagaland to about 38 months in Kerala. The median birth interval in AP was 31 months (Figure 2). In Andhra Pradesh, 13% of births occur within 18 months of a previous birth and 27% occur within 24 months. About 38% of births occur after an interval of 3 years or more (Table 1). Birth intervals are four months shorter among urban women than among rural women.(NFHS-2).

SRS also provides information on birth intervals. The data from SRS on birth intervals is available from the year 1990 onwards (Figure 3). Current live births with a birth interval of 10-12 months were about 3.15% of total births in the early 1990s. This proportion reduced to about 0.9% towards second half of 1990s (1994-98). Percentage of live births with a birth interval 12-18 months stayed almost constant and 10%. Proportion of live births after a birth interval of 24-30 months increased towards the second half of 1990s. For about 15% in early 1990s to about 25% in the late 1990s. During the late 1990s the proportion of live births after 36 months increased , while those after 18-24 months decreased. Thus the birth intervals in AP appear to be improving. Proportion of live births before the critical 2 year birth interval has reduced from 22% from 1990-93 to about 14% between 1994-98.

SRS also provides information on birth intervals. The data from SRS on birth intervals is available from the year 1990 onwards (Figure 3). Current live births with a birth interval of 10-12 months were about 3.15% of total births in the early 1990s. This proportion reduced to about 0.9% towards second half of 1990s (1994-98). Percentage of live births with a birth interval 12-18 months stayed almost constant and 10%. Proportion of live births after a birth interval of 24-30 months increased towards the second half of 1990s. For about 15% in early 1990s to about 25% in the late 1990s. During the late 1990s the proportion of live births after 36 months increased , while those after 18-24 months decreased. Thus the birth intervals in AP appear to be improving. Proportion of live births before the critical 2 year birth interval has reduced from 22% from 1990-93 to about 14% between 1994-98.

Various factors may for example, NFHS-2 found that the median birth interval is slightly shorter if the previous child was a girl than it was a boy (Table 2). Birth intervals are much shorter if the previous child died (25 months) than if the previous child survived (32 months). There is also a tendency for birth intervals to decrease with education. Mothers with at least a high school education have a median birth interval that is six months shorter than the interval for illiterate mothers. Similarly, mothers living in households with a high standard of living have a median birth interval that is six months shorter than the interval for mothers who live in households with a low standard of living. Thus socioeconomic development and spread of education may contribute to reduction in fertility and tend to reduce birth intervals. However, these same factors may improve access to contraceptives, with its resultant effect on birth spacing. Probably the median birth interval may not change much. From reproductive health point of view, the median birth interval of more than 24 months would be acceptable provided the distribution is such that births less than 24 months after the previous birth are brought down to near zero levels. Hence it will be desirable to look at the distribution of birth intervals.

Updated by Samatha Reddy Dated: 18/08/2003