Influence of the Pre-Natal Environment on Post-Natal Growth

The pre-natal environment may modify the state of development of the child at birth by influencing the rate or duration of pre-natal growth. Size of litter, for example, has a substantial effect on both, for in multiple pregnancy foetal growth is retarded during the last weeks of gestation, and onset of labour is earlier than in single pregnancy (McKeown and Record, 1952). Parity also influences the rate of foetal growth, which is greater in later born than in first born (McKeown and Record, 1953), but it has only a small effect on duration of gestation (Karn and Penrose, 1951). Maternal age has little influence on rate of growth, and none on duration of gestation when a correction is introduced for length of cycle (Gibson and Dougray, 1953). These environmental influences are modified after birth. They may be removed, as in the case of the gross pre-natal handicaps associated with multiple pregnancy, or turned in another direction, as in the case of the differences related to birth order (the pre-natal environment favours later born; the post-natal environment favours first born). Postnatal growth therefore reflects both :