Sex of the first-born and risk of preterm birth in the subsequent pregnancy
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Sex of the first-born and risk of preterm birth in the subsequent pregnancy. / Mortensen, Laust H; Nielsen, Henriette Svarre; Cnattingius, Sven; Andersen, Anne-Marie Nybo.
I: Epidemiology, Bind 22, Nr. 3, 2011, s. 328-32.Publikation: Bidrag til tidsskrift › Tidsskriftartikel › Forskning › fagfællebedømt
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TY - JOUR
T1 - Sex of the first-born and risk of preterm birth in the subsequent pregnancy
AU - Mortensen, Laust H
AU - Nielsen, Henriette Svarre
AU - Cnattingius, Sven
AU - Andersen, Anne-Marie Nybo
PY - 2011
Y1 - 2011
N2 - BACKGROUND: Recent data suggest that the chance of successfully maintaining a pregnancy may be influenced by the sex of previously born children. We explored a possible relation between sex of the first-born infant and the risk of preterm birth in the second pregnancy.METHODS: Using data from the National Medical Birth Registries in Denmark 1980-2004 and Sweden 1980-2001, we selected all women whose first and second births were singleton and who had information on sex of first-born infant and gestational age for the second (Denmark, n = 393,686; Sweden, n = 603,282). Cox proportional hazards regression analysis was used to estimate the hazard ratio of preterm birth in the second pregnancy according to the sex of the first-born infant.RESULTS: Compared with women whose first baby was a girl, women with boys had an increased risk of preterm birth in a second pregnancy (hazard ratio = 1.10 [95% confidence interval = 1.07-1.13]). This result was consistent in the 2 populations. The association was not confounded by maternal age, interpregnancy interval, or sex of the second infant or by maternal characteristics that do not vary from one pregnancy to the next.CONCLUSIONS: Exposure to a male fetus may increase a woman's risk of preterm delivery in the next pregnancy. While the findings have no direct public health relevance, they may suggest new pathways by which preterm birth can occur.
AB - BACKGROUND: Recent data suggest that the chance of successfully maintaining a pregnancy may be influenced by the sex of previously born children. We explored a possible relation between sex of the first-born infant and the risk of preterm birth in the second pregnancy.METHODS: Using data from the National Medical Birth Registries in Denmark 1980-2004 and Sweden 1980-2001, we selected all women whose first and second births were singleton and who had information on sex of first-born infant and gestational age for the second (Denmark, n = 393,686; Sweden, n = 603,282). Cox proportional hazards regression analysis was used to estimate the hazard ratio of preterm birth in the second pregnancy according to the sex of the first-born infant.RESULTS: Compared with women whose first baby was a girl, women with boys had an increased risk of preterm birth in a second pregnancy (hazard ratio = 1.10 [95% confidence interval = 1.07-1.13]). This result was consistent in the 2 populations. The association was not confounded by maternal age, interpregnancy interval, or sex of the second infant or by maternal characteristics that do not vary from one pregnancy to the next.CONCLUSIONS: Exposure to a male fetus may increase a woman's risk of preterm delivery in the next pregnancy. While the findings have no direct public health relevance, they may suggest new pathways by which preterm birth can occur.
KW - Chi-Square Distribution
KW - Cohort Studies
KW - Denmark
KW - Female
KW - Gestational Age
KW - Humans
KW - Infant, Newborn
KW - Infant, Premature
KW - Male
KW - Parity
KW - Predictive Value of Tests
KW - Pregnancy
KW - Premature Birth
KW - Prevalence
KW - Proportional Hazards Models
KW - Registries
KW - Risk Assessment
KW - Sex Factors
U2 - 10.1097/EDE.0b013e31820e8600
DO - 10.1097/EDE.0b013e31820e8600
M3 - Journal article
C2 - 21283010
VL - 22
SP - 328
EP - 332
JO - Epidemiology
JF - Epidemiology
SN - 1044-3983
IS - 3
ER -
ID: 34164594