Birthweight is a strong determinant of a neonate’s health. The SARS-CoV-2 pandemic’s impact on birthweight has not been investigated in-depth, with inconsistent conclusions from initial studies. To assess changes in preterm birth and inappropriate birthweight between the SARS-CoV-2 pandemic and pre-pandemic periods. A nationwide birth micro-data consisted with exhaustive census of all births in 2011–2020 in South Korea was accessed to examine whether the mean birthweight and rates of under/overweight births changed significantly during the SARS-CoV-2 pandemic year (2020) compared to those of the pre-pandemic period (2011–2019). A total of 3,736,447 singleton births were analyzed. Preterm birth was defined as < 37 weeks of gestation. Low birthweight (LBW) and macrosomia were defined as birthweights < 2.5 kg and ≥ 4.0 kg, respectively. Small for gestational age (SGA) and large for gestational age (LGA) were defined as birthweights below the 10th and above 90th percentiles for sex and gestational age, respectively. Inappropriate birthweight was defined as one or more LBW, macrosomia, SGA, or LGA. Generalized linear models predicted birth outcomes and were adjusted for parental age and education level, marital status, parity, gestational age, and months from January 2011. There were 3,481,423 and 255,024 singleton births during the pre-pandemic and pandemic periods, respectively. Multivariable generalized linear models estimated negative associations between the pandemic and preterm birth (odds ratio [OR], 0.968; 95% confidence interval [CI] 0.958–0.978), LBW (OR: 0.967, 95% CI 0.956–0.979), macrosomia (OR: 0.899, 95% CI 0.886–0.912), SGA (OR: 0.974, 95% CI 0.964–0.983), LGA (OR: 0.952, 95% CI 0.945–0.959), and inappropriate birthweight (OR: 0.958, 95% CI 0.952–0.963), indicating a decline during the pandemic compared to pre-pandemic period. An 8.98 g decrease in birthweight (95% CI 7.98–9.99) was estimated during the pandemic. This is the largest and comprehensive nationwide study to date on the impact of the SARS-CoV-2 pandemic on preterm birth and inappropriate birthweight. Birth during the pandemic was associated with lower odds of being preterm, underweight, and overweight. Further studies are required to understand the dynamics underlying this phenomenon.

Women with twin pregnancies who gave birth between 2007 and 2016 were included. ResultsFrom 2007 to 2016, the rate of twin pregnancies increased (1.37% vs. 1.91%, respectively, P<0.0001).

ObjectiveTo evaluate long‐term adverse neurodevelopmental outcomes of discordant twins delivered at term.DesignRetrospective cohort study.SettingNationwide (Republic of Korea).PopulationAll twin children delivered at term between 2007 and 2010.MethodsThe study population was divided into two groups according to inter‐twin birthweight discordancy: the ‘concordant twin group’, twin pairs with inter‐twin birthweight discordancy less than 20%; and the ‘discordant twin group’, twin pairs with inter‐twin birthweight discordancy of 20% or more. The risk of long‐term adverse neurodevelopmental outcomes was compared between the concordant twin group and the discordant twin group. Long‐term adverse neurodevelopmental outcomes between smaller and larger twin children within twin pairs were further analysed. The composite adverse neurodevelopmental outcome was defined as the presence of at least one of the following: motor developmental delay, cognitive developmental delay, autism spectrum disorders/attention deficit hyperactivity disorders, tics/stereotypical behaviour or epileptic/febrile seizure.Main Outcome MeasuresLong‐term adverse neurodevelopmental outcome.ResultsOf 22 468 twin children (11 234 pairs) included, 3412 (15.19%) twin children were discordant. The risk of composite adverse neurodevelopmental outcome was higher in the discordant twin group than in the concordant twin group (adjusted hazard ratio [HR] 1.13, 95% CI 1.03–1.24). The long‐term adverse neurodevelopmental outcomes were not significantly different between smaller and larger twin children in discordant twin pairs (adjusted HR 1.01, 95% CI 0.81–1.28).ConclusionIn twin pairs delivered at term, an inter‐twin birthweight discordancy of 20% or greater was associated with long‐term adverse neurodevelopmental outcomes; and long‐term adverse neurodevelopmental outcomes were not significantly different in smaller or larger twin children in discordant twin pairs.