417 portable infantometer

Child birthweight was assessed by hospital nurses immediately after delivery—with a Tanita BD-815U neonatal scale (Arlington Heights, IL, USA) provided by the study which measured grams to two decimal places—and was retrospectively abstracted from hospital records. Study nurses measured birth length and head circumference within the first 24 to 48 hours of birth. Birth length was measured using a Seca 417 portable infantometer (Chino, CA, USA), with the infant laid on his or her back, legs aligned and fully extended, and toes pointing directly upward. Head circumference was assessed to the nearest 0.1 cm using a tape measure positioned just above the eyebrows, above the ears, and around the largest part of the back of the head. Measurements were taken in triplicate and averaged. For each size outcome, growth z-scores for gestational age and sex were constructed according to WHO Child Growth Standards [20 ]. Gestational age was ascertained by last menstrual period (LMP) reported at delivery, with unlikely values (above the 1^st or below the 99^th birthweight-for-age percentiles) replaced by gestational age indicated in medical records for 10% of participants. Birth size measurements were complete for all but one missing birth weight and six missing length and head circumference measurements.

International standardized protocols were used to guide measurement of anthropometric data²⁰ . As previously described by Iannotti et al. (2017), study enumerators participated in 3-day training and validation exercises. Enumerator pairs each took measurements of child length to the nearest 1 mm using a Seca 417 portable infantometer. If measures differed by 5 mm or more, a third measurement was made, and the result was averaged with the closest measure. A Seca Model 874 Electronic Digital Scale, with mother/child tare feature to the nearest 0.01, was used to measure weight. If the two measures taken differed by 0.05 kg or more, a third measure was made, and the results averaged. Measures were converted to z scores for length-for-age (LAZ), weight-for-age (WAZ), weight-for-length (WLZ), and BMI (BMIz)^{11 (link)}. Stunting is defined as length-for-age z score (LAZ) < − 2²⁰ .