Objective: Determine the distribution of birthweights in singleton births by gestational age and gender at Marquette General Hospital, a rural referral center in Michigan's upper peninsula.
Study design: Birth log data were examined for prenatal factors and obstetrical outcomes. The birthweight distribution was compared to published values, and a linear regression model of prenatal factors was developed.
Results: Our median birthweights were significantly greater than published values. Males were 128 g heavier than female infants after adjusting for gestational age. In a multivariable linear regression model, birthweight was significantly associated with gestational age, sex of the infant, maternal age, primigravida status of mother, and maternal diabetes (all p<0.01). Using published standards resulted in an overdiagnosis of large for gestational age and an underdiagnosis of small for gestational age.
Conclusion: Local birthweight distributions can differ significantly from historical or national distributions. The development of birthweight distributions accommodating for prenatal factors is needed.