As smoking status is recorded at two points in time only, the data will not show if mothers were smoking throughout the duration of their pregnancy, or how frequently they smoked.
Er nad oes ganddo arwyddocâd ystadegol bob tro, mae’r patrwm cyson lle gwelir gostyngiadau ar draws y cynlluniau’n awgrymu bod y ddau gynllun yn gwella iechyd anadlol.