Young maternal age and preterm labor.

PURPOSE: The relationship among young age, biologic immaturity (as indexed by low gynecologic age), and the causes of preterm delivery (idiopathic preterm labor [PTL], premature rupture of the membranes [PROM], and medical indications) were investigated among 605 primigravidas from the Camden Study.

METHODS

The sample consisted of 366 young adolescents < 16 years at the time of their last menstrual period (LMP) and 239 older women, 18-29 years at LMP (controls). The young adolescents were significantly shorter, thinner, had younger ages at menarche, and over a third (36.3%) were of low gynecologic age, i.e., their chronologic age was 2 or fewer years more than their age at menarche.

RESULTS

Adjusting for ethnicity, cigarettes smoked/day, weight gain rate, height, fetal sex, gestational diabetes mellitus, and pregnancy-induced hypertension, young adolescents overall had a nearly 75% increased risk of PTL (adjusted odds ratio [AOR] = 1.74, 95% confidence interval [95% CI]: 1.07-2.84), and preterm delivery with PTL (AOR = 2.08, 95% CI: 1.08-4.00). There was a modest decreased risk of preterm delivery among young gravidas attributable to other causes, such as PROM or medical indications (AOR = 0.70, 95% CI: 0.28-1.75). This increased risk of PTL and preterm delivery with PTL was principally attributable to biologic immaturity. Young age with low gynecologic age was associated with a twofold risk of PTL (AOR = 2.15, 95% CI: 1.19-3.89) and preterm delivery with PTL (AOR = 2.64, 95% CI: 1.23-5.65), while the risk associated with young age and higher gynecologic age was only increased moderately.

CONCLUSIONS

Young adolescents, and especially those of low gynecologic age, appear prone to PTL and are at increased risk for preterm delivery through this pathway.