title: Body size and time-to-pregnancy in black women.
abstract: OBJECTIVE
  Are overall and central obesity associated with reduced fecundability in US black women?
  
  
  CONCLUSIONS
  Overall and central obesity--based on self-reported measures of body mass index (BMI, kg/m(2)), waist circumference and waist-to-hip ratio--were independent risk factors for subfertility in our cohort.
  
  
  BACKGROUND
  Overall obesity (BMI ≥ 30 kg/m(2)) has been associated with infertility in several studies. The role of central obesity is less clear. There are no previous studies of time-to-pregnancy (TTP) in black women.
  
  
  METHODS
  Data were derived from the Black Women's Health Study, a prospective cohort study. During 1995-2011, there were 2239 planned pregnancy attempts reported by 1697 women, resulting in 2022 births. Cohort retention was greater than 80%.
  
  
  METHODS
  Eligible women were aged 21-40 years and reported at least one planned pregnancy attempt during 1995-2011. Height and weight were reported in 1995, with weight updated every two years; waist and hip circumferences were reported in 1995 and updated in 2003. A validation study within the cohort showed high correlations between self-reported and technician-measured weight (r = 0.97), height (r = 0.93), waist circumference (r = 0.75) and hip circumference (r = 0.74). In 2011, TTP was reported in months. Proportional probabilities regression models were used to estimate fecundability ratios (FRs) and 95% confidence intervals (CI), adjusting for covariates.
  
  
  RESULTS
  High BMI was associated with delayed conception: relative to BMI 18.5-24.9, FRs for BMI categories of <18.5, 25.0-29.9, 30.0-34.9 and ≥ 35.0 were 0.92 (CI: 0.64-1.32), 0.93 (CI: 0.84-1.03), 0.92 (CI: 0.79-1.06) and 0.73 (CI: 0.61-0.87), respectively. Associations were stronger among nulliparous women (P-interaction = 0.003). After controlling for BMI, reduced fecundability was observed among women with large waist circumferences (≥ 33 versus <26 inches: FR = 0.73, CI: 0.60-0.88) and large waist-to-hip ratios (≥ 0.85 versus <0.71: FR = 0.83, CI: 0.71-0.97).
  
  
  CONCLUSIONS
  TTP was reported retrospectively and error in recall is likely, particularly as time since the pregnancy increases. However, results were similar when based on the most recent versus first pregnancies. Confounding may have been introduced by the lack of control for important determinants of TTP. Nevertheless, control for maternal age and education, which are highly correlated with TTP determinants such as paternal age and persistence in trying, should reduce the extent of confounding. The analysis was confined to planned pregnancies. If pregnancy intention was related both to body size and fecundability, our results could be biased. Bias is likely to be small because we found little difference in body size and other measured characteristics between pregnancy planners and non-planners.
  
  
  CONCLUSIONS
  Our findings add to the growing body of literature showing that excess BMI is associated with reduced fecundability and further suggest that central obesity is an important independent risk factor for infertility. The relation of obesity to infertility is especially relevant to US black women because they have higher rates of obesity and infertility. Reductions in overall and central obesity may offer the potential to improve fertility outcomes.
  
  
  BACKGROUND
  This work was funded by National Cancer Institute grant CA58420. We have no competing interests to report.
authors: Slone Epidemiology Center at Boston University, 1010 Commonwealth Avenue, Boston, MA 02215, USA.
authors: Lauren A
authors: LA
authors: Wise
authors: Julie R
authors: JR
authors: Palmer
authors: Lynn
authors: L
authors: Rosenberg
mesh_terms: D000328:Adult; D001741:Black or African American / Q000208:ethnology*; D015992:Body Mass Index; D049628:Body Size; D015331:Cohort Studies; D005260:Female; D006801:Humans; D007247:Infertility, Female / Q000150:complications*; D009765:Obesity / Q000150:complications*; D012044:Regression Analysis; D061685:Time-to-Pregnancy; D055105:Waist Circumference; D049629:Waist-Hip Ratio
keywords: African Americans; body mass index; cohort study; fertility; obesity
references: Hum Reprod. 2010 Jan;25(1):253-64
references: 19828554
references: Hum Reprod. 2009 Jan;24(1):226-32
references: 18819963
references: Epidemiology. 1999 Jul;10(4):422-8
references: 10401878
references: Am J Epidemiol. 2010 Dec 1;172(11):1286-91
references: 20937635
references: JAMA. 2006 Apr 5;295(13):1549-55
references: 16595758
references: Hum Reprod. 2007 Feb;22(2):414-20
references: 17095518
references: Hum Reprod. 2008 Nov;23(11):2555-63
references: 18641044
references: Biometrics. 1997 Mar;53(1):318-29
references: 9147597
references: Am J Epidemiol. 2005 Jul 15;162(2):115-24
references: 15972942
references: Metabolism. 1999 Jan;48(1):107-12
references: 9920153
references: J Clin Endocrinol Metab. 2009 May;94(5):1533-40
references: 19223519
references: Hum Reprod. 2007 Sep;22(9):2488-93
references: 17636282
references: Metabolism. 1984 Jan;33(1):68-75
references: 6361449
references: Fertil Steril. 2010 Feb;93(3):681-90
references: 19939362
references: Fertil Steril. 1995 May;63(5):1005-8
references: 7720908
references: N Engl J Med. 1988 Jul 28;319(4):189-94
references: 3393170
references: Cancer Causes Control. 1996 Mar;7(2):253-63
references: 8740738
references: Ethn Dis. 2006 Autumn;16(4):943-7
references: 17061751
references: Am J Obstet Gynecol. 1994 Jul;171(1):171-7
references: 8030695
references: Am J Hum Genet. 1985 Mar;37(2):362-72
references: 3985011
references: Am J Epidemiol. 1993 Mar 1;137(5):577-84
references: 8465809
references: Fertil Steril. 1996 Mar;65(3):503-9
references: 8774277
references: Int J Epidemiol. 2000 Oct;29(5):856-61
references: 11034969
references: Paediatr Perinat Epidemiol. 2011 Sep;25(5):460-5
references: 21819427
references: BMJ. 1993 Feb 20;306(6876):484-7
references: 8448457
references: J Endocrinol Invest. 2009 Feb;32(2):98-101
references: 19411803
references: Obesity (Silver Spring). 2007 Apr;15(4):986-93
references: 17426334
references: Hum Reprod. 1987 Aug;2(6):521-33
references: 3117838
references: Gynecol Obstet Invest. 1999;47(1):1-5
references: 9852383
references: Hum Reprod. 1997 Jul;12(7):1448-53
references: 9262276
references: J Clin Endocrinol Metab. 1994 Oct;79(4):1105-9
references: 7962282
references: Sex Transm Dis. 1987 Jan-Mar;14(1):12-6
references: 3563829
references: Epidemiology. 2002 Mar;13(2):184-90
references: 11880759
references: Stat Med. 1997 Jan 15-Feb 15;16(1-3):215-24
references: 9004393
references: Epidemiology. 2005 May;16(3):346-54
references: 15824551
references: Fertil Steril. 2008 Nov;90(5):1640-8
references: 18321499
references: Am J Epidemiol. 2012 Sep 15;176(6):506-11
references: 22904203
references: Paediatr Perinat Epidemiol. 2007 Jul;21 Suppl 1:8-12
references: 17593191
references: Fertil Steril. 2004 Feb;81(2):384-92
references: 14967378
references: Am J Epidemiol. 2000 Jun 1;151(11):1072-9
references: 10873131
references: Med Sci Sports Exerc. 1993 Jan;25(1):81-91
references: 8423759
references: Obes Rev. 2001 Nov;2(4):231-8
references: 12119994
references: Hum Reprod. 2007 Feb;22(2):407-13
references: 17000648
references: World Health Organ Tech Rep Ser. 1995;854:1-452
references: 8594834
references: Ann Intern Med. 1995 Mar 1;122(5):327-34
references: 7847643
references: Am J Epidemiol. 1999 Dec 15;150(12):1316-24
references: 10604774
references: Epidemiology. 2009 Jan;20(1):56-9
references: 19057382
references: Am J Epidemiol. 1993 Jan 1;137(1):1-8
references: 8434568
references: Biometrics. 2000 Dec;56(4):1023-9
references: 11129457
references: Hum Reprod. 2003 Sep;18(9):1959-66
references: 12923157
references: Hum Reprod. 1997 Sep;12(9):2057-60
references: 9363729
references: Am J Clin Nutr. 2009 Feb;89(2):500-8
references: 19116329
references: Ann N Y Acad Sci. 1994 Feb 18;709:179-95
references: 8154701
references: J Clin Endocrinol Metab. 1990 Feb;70(2):473-9
references: 2298859
references: Am J Phys Anthropol. 2006 Oct;131(2):295-302
references: 16596596
references: J Am Med Womens Assoc (1972). 1995 Mar-Apr;50(2):56-8
references: 7722208
references: Hum Reprod. 2007 Jun;22(6):1634-7
references: 17344224
references: J Natl Black Nurses Assoc. 2010 Dec;21(2):9-15
references: 21516920
references: Epidemiology. 1994 Mar;5(2):247-50
references: 8173001
references: Epidemiology. 2006 Sep;17(5):520-3
references: 16837825
references: Hum Reprod. 2005 Jan;20(1):208-15
references: 15567884
references: Stat Med. 1994 Mar 15-Apr 15;13(5-7):671-81
references: 8023042