What factors are related to recurrent preterm birth among underweight women?
OBJECTIVE
Our objective was to identify factors associated with recurrent preterm birth among underweight women.


METHODS
Maternally linked hospital and birth certificate records of deliveries in California between 2007 and 2010 were used. Consecutive singleton pregnancies of women with underweight body mass index (BMI <18.5 kg/m2) in the first pregnancy were analyzed. Pregnancies were categorized based on outcome of the first and second birth as: term-term; term-preterm; preterm-term and preterm-preterm.


RESULTS
We analyzed 4971 women with underweight BMI in the first pregnancy. Of these, 670 had at least one preterm birth. Among these 670, 86 (21.8%) women experienced a recurrent preterm birth. Odds for first term - second preterm birth were decreased for increases in maternal age (aOR: 0.90, 95%CI: 0.95-0.99) whereas inter-pregnancy interval <6 months was related to both first term - second preterm birth (aOR:1.66, 95%CI: 1.21-2.28) and first preterm birth - second term birth (aOR: 1.43, 95%CI: 1.04-1.96). Factors associated with recurrent preterm birth were: negative or no change in pre-pregnancy weight between pregnancies (aOR: 1.67, 95%CI: 1.07-2.60), inter-pregnancy interval <6 months (aOR: 2.14, 95%CI: 1.29-3.56), and maternal age in the first pregnancy (aOR: 0.93, 95%CI: 0.90-0.97).


CONCLUSIONS
Recurrent preterm birth among underweight women was associated with younger age, short inter-pregnancy interval, and negative or no weight change between pregnancies.
a Department of Obstetrics & Gynecology , Stanford University School of Medicine , Stanford , CA , USA.
Anna I
AI
Girsen
b March of Dimes Prematurity Research Center, Division of Developmental & Neonatal Medicine, Department of Pediatrics , Stanford University School of Medicine , Stanford , CA , USA.
Jonathan A
JA
Mayo
b March of Dimes Prematurity Research Center, Division of Developmental & Neonatal Medicine, Department of Pediatrics , Stanford University School of Medicine , Stanford , CA , USA.
Matthew B
MB
Wallenstein
b March of Dimes Prematurity Research Center, Division of Developmental & Neonatal Medicine, Department of Pediatrics , Stanford University School of Medicine , Stanford , CA , USA.
Jeffrey B
JB
Gould
b March of Dimes Prematurity Research Center, Division of Developmental & Neonatal Medicine, Department of Pediatrics , Stanford University School of Medicine , Stanford , CA , USA.
Suzan L
SL
Carmichael
b March of Dimes Prematurity Research Center, Division of Developmental & Neonatal Medicine, Department of Pediatrics , Stanford University School of Medicine , Stanford , CA , USA.
David K
DK
Stevenson
b March of Dimes Prematurity Research Center, Division of Developmental & Neonatal Medicine, Department of Pediatrics , Stanford University School of Medicine , Stanford , CA , USA.
Deirdre J
DJ
Lyell
b March of Dimes Prematurity Research Center, Division of Developmental & Neonatal Medicine, Department of Pediatrics , Stanford University School of Medicine , Stanford , CA , USA.
Gary M
GM
Shaw
D000293:Adolescent; D000328:Adult; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D011247:Pregnancy; D011248:Pregnancy Complications; D047928:Premature Birth / Q000209:etiology*; D012008:Recurrence; D012189:Retrospective Studies; D012307:Risk Factors; D013851:Thinness; D055815:Young Adult
Preterm birth; body mass index; high-risk pregnancy; inter-pregnancy interval; recurrence; underweight