Singleton birthweight by gestational age following in vitro fertilization in the United States

Assisted reproductive technology has been reported to account for a disproportionate higher number of low birthweight infants, even in singleton births. Low birthweight infants occur from preterm birth, decreased intrauterine growth, or both. It is unclear whether infants conceived by in vitro fertilization (IVF) have a reduced intrauterine growth rate or intrauterine growth restriction. Growth-restricted newborns have higher perinatal morbidity and are at increased risk for adult-onset illnesses. To date, there are no national standards for birthweight percentiles by gestational week, allowing for fetal growth assessment of singletons conceived by assisted reproductive technology in the United States.

The objective of the study was to establish US singleton IVF reference standards using birthweight percentiles by gestational age for singleton live births resulting from IVF in the United States.

We studied birthweight by completed weeks of gestation for 93,443 singleton IVF births reported to the Society for Assisted Reproductive Technologies, 2006-2010. The third to 97th birthweight percentiles per completed week of gestation for weeks between 24 and 42 were calculated and were compared with recently published birthweight percentiles by gestational age for 3,812,730 US singleton births in 2011.

Smoothed birthweight for gestational age charts and curves were created for all US IVF singletons and female-male singletons from 24 to 42 weeks. Over the span of 31-41 weeks of gestation, the 10th, 50th, and 90th birthweight percentile values of IVF singletons were comparable with recently published birthweight percentile values of US singletons. At 40 completed weeks of gestation, the 10th, 50th, and 90th birthweight percentiles of all IVF singletons were 3078, 3506, and 4053 g, as compared with corresponding 3005, 3499, and 4057 g of US singletons. The 10th, 50th, and 90th birthweight percentile values for female and male IVF singletons were also comparable with US female and male singletons.

Birthweight percentiles per completed week of gestation of IVF and US singletons are approximately equal from 31 until 41 completed weeks, suggesting that intrauterine growth is not reduced in IVF singleton infants.