title: Fetal head circumference, operative delivery, and fetal outcomes: a multi-ethnic population-based cohort study.
abstract: BACKGROUND
  Operative delivery procedures, such as primary cesarean section, vacuum-assisted, and forceps-assisted vaginal delivery increase maternal and fetal morbidity, and the cost of care. We evaluated whether large fetal head circumference (FHC) independently increases risk of such interventions, as well as fetal distress or low Apgar score, in anatomically normal infants.
  
  
  METHODS
  We conducted a population-based retrospective cohort study using Washington State birth certificate data. We included singleton, term infants born to nulliparous mothers from 2003-2009. We compared mode of delivery and fetal outcomes in 10,750 large-FHC (37-41 cm) infants relative to 10,750 average-FHC (34 cm) infants, frequency matched by birth-year.
  
  
  RESULTS
  Large-FHC infants were nearly twice as likely to be delivered by primary cesarean section as average-FHC infants (unadjusted relative risk [RR] 1.84, 95% confidence interval [CI]: 1.77, 1.92). The RR for primary cesarean section associated with large-FHC was largest for mothers aged 19 years or less (RR 2.28; 95% CI: 1.99, 2.61), and smallest for mothers aged 35 years or greater (RR 1.51; 95% CI: 1.37, 1.66) [test of homogeneity, p < 0.001]. Large-FHC infants were at increased risk of vacuum-assisted vaginal delivery (RR 1.55; 95% CI: 1.43, 1.69), and forceps-assisted vaginal delivery (RR 1.61; 95% CI: 1.32, 1.97). There was no difference in risk of fetal distress (RR 0.97; 95% CI: 0.89, 1.07) for large-FHC versus average-FHC infants. Risk estimates were unaffected by adjustment for potential confounders.
  
  
  CONCLUSIONS
  Nulliparous mothers of large-FHC infants are at increased risk of primary cesarean section, vacuum-assisted and forceps-assisted vaginal delivery relative to mothers of average-FHC infants. Maternal age modifies the association between FHC and primary cesarean section.
authors: Andrew
authors: A
authors: Mujugira
authors: Alfred
authors: A
authors: Osoti
authors: Ruth
authors: R
authors: Deya
authors: Stephen E
authors: SE
authors: Hawes
authors: Amanda I
authors: AI
authors: Phipps
mesh_terms: D000293:Adolescent; D000328:Adult; D001741:Black or African American / Q000706:statistics & numerical data; D001034:Apgar Score; D001213:Asian / Q000706:statistics & numerical data; D002508:Cephalometry; D002585:Cesarean Section / Q000706:statistics & numerical data*; D015331:Cohort Studies; D005113:Extraction, Obstetrical / Q000706:statistics & numerical data; D005260:Female; D005316:Fetal Distress / Q000453:epidemiology*; D005333:Fetus / Q000033:anatomy & histology*; D006257:Head / Q000033:anatomy & histology*; D006630:Hispanic or Latino / Q000706:statistics & numerical data; D006801:Humans; D007198:Indians, North American / Q000706:statistics & numerical data; D007231:Infant, Newborn; D008297:Male; D044468:Native Hawaiian or Pacific Islander / Q000706:statistics & numerical data; D009929:Organ Size; D011247:Pregnancy; D012189:Retrospective Studies; D012307:Risk Factors; D014481:United States / Q000453:epidemiology; D014620:Vacuum Extraction, Obstetrical / Q000706:statistics & numerical data*; D044465:White People / Q000706:statistics & numerical data; D055815:Young Adult
references: Am J Obstet Gynecol. 1997 Mar;176(3):667-71
references: 9077626
references: Bone. 2010 Oct;47(4):773-82
references: 20637322
references: Am J Clin Nutr. 2000 Jul;72(1 Suppl):291S-297S
references: 10871595
references: Natl Vital Stat Rep. 2011 Nov 3;60(1):1-70
references: 22670489
references: J Pediatr Adolesc Gynecol. 2012 Jun;25(3):190-4
references: 22578479
references: Obstet Gynecol. 2003 Sep;102(3):628-36
references: 12962954
references: Birth. 2002 Sep;29(3):157-61
references: 12153645
references: Obstet Gynecol. 2005 Dec;106(6):1469-70
references: 16319282
references: Am J Public Health. 1984 May;74(5):505-6
references: 6711731
references: Ultrasound Obstet Gynecol. 2011 Jan;37(1):65-71
references: 20661958
references: Acta Obstet Gynecol Scand. 2012 Apr;91(4):470-5
references: 22229662
references: Br J Obstet Gynaecol. 1998 Jun;105(6):621-6
references: 9647152
references: Acta Obstet Gynecol Scand. 2004 Dec;83(12):1178-83
references: 15548152
references: J Obstet Gynaecol. 2003 Sep;23(5):496-9
references: 12963505
references: Am J Obstet Gynecol. 2009 Jul;201(1):91.e1-7
references: 19481726
references: Lancet. 2006 Jun 3;367(9525):1819-29
references: 16753484
references: Obstet Gynecol. 2006 Jun;107(6):1253-60
references: 16738149
references: Am J Public Health. 1994 Sep;84(9):1414-20
references: 8092364
references: Paediatr Perinat Epidemiol. 2005 Nov;19(6):460-71
references: 16269074
references: J Natl Med Assoc. 1987 Apr;79(4):377-80
references: 3586034
references: Am J Obstet Gynecol. 2005 Mar;192(3):789-94
references: 15746673