The Effect of Maternal Age at the First Childbirth on Gestational Age and Birth Weight: The Japan Environment and Children’s Study (JECS)

Abstract

Background: In Japan, mean maternal age at first childbirth is increasing. The aim of this study was to investigate whether maternal age at the first childbirth is a risk factor for preterm birth (PTB), low birth weight (LBW), and small for gestational age (SGA). Methods: We used the results of Japan Environment and Children’s Study (JECS) who gave birth in 2011–2014. Cases of primiparous singleton pregnancies where the subject was ≥20 years and delivered after 22 weeks were included. All subjects were categorized into five groups according to maternal age: 20–24, 25–29, 30–34, 35–39, and ≥40 years. Adjusted odds ratios (aORs) for PTB (before 37 and 34 weeks), LBW (30 years. The aORs of PTB before 37 and 34 weeks, LBW 30 years) at the first childbirth was an independent risk factor for PTB, LBW, and SGA.

Keywords

• maternal age
• preterm birth
• first delivery
• low birth weight
• birth cohort study