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Twins delivered before 37 weeks gestation had higher risks of short- and long-term complications, according to a population study in Scotland.

Infants of twin pregnancies born from 34 to 37 weeks had a higher risk of perinatal death compared with twins born closer to normal term, reported Sarah Murray, PhD, of the University of Edinburgh, and colleagues.

Specifically, babies born at 34 weeks gestation had more than 2.5 times increased risk (adjusted odds ratio 2.59, 95% CI 1.99-3.39), and those born at 35 weeks had 2.12 times greater risk (AOR 2.12, 95% CI 1.63-2.76) of perinatal mortality compared with babies that remained in utero for 37 completed weeks, they wrote in .

Also, infants delivered at 36 weeks had nearly double the risk of perinatal mortality versus those delivered at 37 weeks (AOR 1.99, 95% CI 1.53-2.69).

And compared with twins born at 37 completed gestation weeks, infants delivered earlier also had greater odds of special education need in school, the authors found.

However, there was no significant risk of perinatal mortality after 37 weeks gestation, they stated.

"The findings of this study suggest that birth at 37 completed weeks of gestation may be associated with optimal short- and long-term outcomes for twin infants," Murray and colleagues wrote, adding that this was the first nationwide study known to investigate long-term outcomes of twins across multiple gestation age categories.

Kjersti Aagaard, MD, of the Baylor College of Medicine and Texas Children's Hospital in Houston, said that analyzing the long-term outcomes associated with gestation age was significant, especially in regards to school performance and social and behavioral outcomes. "That was very valuable to take this long-term view, because that's what parents really care about," said Aagaard, who was not involved in the study, in an interview with 乌鸦传媒.

However, she said that these findings may not apply to both fraternal and identical twins. "We know that monochorionic pregnancies have unique risks that need to be managed appropriately," Aagaard explained. Monochorionic pregnancies, in which two babies share one placenta, are typically higher risk and may be recommended for earlier delivery, she said.

"We need to be mindful that the recommendations in those situations will be different," Aagaard stated.

She suggested a patient-centered approach, advising that women work with their providers to understand distinctions that may influence optimal delivery timing for their pregnancy.

The number of twin pregnancies is rising, in part due to increased use of assisted reproductive treatment, the authors wrote. Although twin pregnancies make up only 3% of live births, they account for 15% of neonatal and special care baby admissions.

Because twin pregnancies have greater risk of perinatal mortality and neonatal death, the researchers said that optimizing birth timing is a key strategy to improving health outcomes. But optimum timing for twin births still remains inconclusive, they added.

They analyzed more than 43,000 twin pregnancies delivered in Scotland at or after 34 weeks, from January 1980 to December 2015. They observed data from the Scottish Morbidity Record, the Scottish Stillbirth and Infant Death Survey, and the Scottish Exchange of Educational Data to link gestation age at birth to perinatal mortality and special education need.

Special education need was defined as any record of intellectual disabilities, dyslexia, physical or motor impairment, speech disorders, autism spectrum disorder, or social, emotional, or behavioral difficulties. The findings on educational outcomes were limited to dichorionic pregnancies, which were identified by sex discordance.

Births were excluded if there was a congenital disorder, birth weight was more than 11 lbs, gestational age was more than 44 weeks, or parity was more than 14. The authors excluded births with missing information on fetal sex, parity, and gestational age.

Around half of the infants included in the study were female, and a majority were born from 37 to 38 weeks gestation. The researchers recorded 472 perinatal deaths, 354 stillbirths, and 118 neonatal deaths. Education data was available for 9,519 infants, 14% of which had a special education need in school. About 60% of mothers were from ages 25 to 35 years at the time of delivery, and approximately half were delivering their first child.

Babies in all gestational age groups before 37 weeks also had an increased risk for special education need later in childhood. Infants born at both 34 and 35 weeks gestation had a 1.35 times greater risk of special education need in school versus babies that remained in utero. Infants born at 36 weeks had similar risk of education needs (AOR 1.39, 95% CI 1.11-1.74).

Study limitations included missing potential confounders, such as chorionicity and conception status, which limited generalizability of results. In addition, the special education analysis was limited because only twins of different sexes could be linked to education data. Therefore, those results may only be relevant for fraternal twin pregnancies, the authors said.

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