Interpregnancy interval. Association with birth weight, stillbirth, and neonatal death.

Pairs of first and second births and pairs of second and third births to the same Norwegian mothers were studied to determine the association between interpregnancy interval and birth weight, stillbirth, and neonatal death. Use of the pair approach provides one birth which could possibly have been affected by the length of the interval and one birth which could not. The association of interval and birth weight for births which precede an interval is found to be equivalent to that for births which follow an interval. The data on stillbirth are compatible with higher rates at long intervals while the data on neonatal death are consistent with higher rates at short intervals. However, we conclude that manipulation of the interval between pregnancies is unlikely to have any marked, direct, beneficial effect on outcome of pregnancy.