Postnatal catch-up growth in term newborns with altered fetal weight patterns. The GROWIN study.

Background: Small for gestational age (SGA) perform a postnatal catch-up growth to recover their genetic trajectory. We studied the postnatal catch-up growth pattern of fetuses born with an appropriate-for-gestational-age (AGA) weight but with fetal growth deceleration (FGD) to explore whether they catch up.

Methods: Nine hundred and sixty-six newborns at Villalba University General Hospital (HUGV), were followed from 34 to 37 weeks to birth. Z-scores, adjusted for sex and age, of weight, length, and BMI at 3, 6, 9, and 12 months were calculated. We define catch-up as an increase in z-score greater than 0.67 SD in the growth curves.

Results: AGA FGD had lower mean weight and length than AGA non-FGD at all time points; BMI was lower until 3 months. AGA FGD had a lower weight, length, and BMI z-score (until 9, 6 months, and at birth, respectively) than AGA non-FGD. AGA FGD newborns had a significantly increased likelihood of weight catch-up at 3 months (OR 1.79; 95% CI: 1.16, 2.78; p = 0.009) and BMI in all investigated periods (OR 1.90; 95% CI 1.30, 2.78; p < 0.001 at 3 months), compared to AGA non-FGD newborns.

Conclusions: AGA FGD newborns perform catch-up growth, especially in weight and BMI, in the first year of life, compared to AGA non-FGD.

Impact: Appropriate-for-gestational-age (AGA) newborns with fetal growth deceleration (FGD), between the third trimester of pregnancy and delivery, present a lower weight and height, during the first year of life, compared to AGA non-FGD. Appropriate-for-gestational-age (AGA) newborns with fetal growth deceleration (FGD), between the third trimester of pregnancy and delivery, present a higher likelihood of weight catch-up in the first 3 months of life and of BMI in the first year compared to AGA non-FGD. AGA FGD experienced early weight and BMI catch-up, especially in the first 3 months of life, like SGA. This finding should be considered in the future follow-up.