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Effects of ultrasound pregnancy dating on neonatal morbidity in late preterm and early term male infants: a register-based cohort study
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Women's and Children's Health, Obstetrics and Gynaecology. Vastmanland Cty Hosp, Clin Res Ctr, Vasteras, Sweden.;Vastmanland Cty Hosp, Dept Obstet & Gynecol, Vasteras, Sweden..
Karolinska Inst, Ctr Pharmacoepidemiol CPE, Dept Med, Stockholm, Sweden..
Karolinska Inst, Ctr Pharmacoepidemiol CPE, Dept Med, Stockholm, Sweden..
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Women's and Children's Health, Obstetrics and Gynaecology.ORCID iD: 0000-0002-4935-7532
2016 (English)In: BMC Pregnancy and Childbirth, ISSN 1471-2393, E-ISSN 1471-2393, Vol. 16, article id 335Article in journal (Refereed) Published
Abstract [en]

Background: Assessing gestational age by ultrasound can introduce a systematic bias due to sex differences in early growth. Methods: This cohort study included data on 1,314,602 births recorded in the Swedish Medical Birth Register. We compared rates of prematurity-related adverse outcomes in male infants born early term (gestational week 37-38) or late preterm (gestational week 35-36), in relation to female infants, between a time period when pregnancy dating was based on the last menstrual period (1973-1978), and a time period when ultrasound was used for pregnancy dating (1995-2010), in order to assess the method's influence on outcome by fetal sex. Results: As expected, adverse outcomes were lower in the later time period, but the reduction in prematurity-related morbidity was less marked for male than for female infants. After changing the pregnancy dating method, male infants born early term had, in relation to female infants, higher odds for pneumothorax (Cohort ratio [CR] 2. 05; 95 % confidence interval [CI] 1.33-3.16), respiratory distress syndrome of the newborn (CR 1.99; 95 % CI 1.33-2. 98), low Apgar score (CR 1.26; 5 % CI 1.08-1.47), and hyperbilirubinemia (CR 1.12; 95 % CI 1.06-1.19), when outcome was compared between the two time periods. A similar trend was seen for late preterm male infants. Conclusion: Misclassification of gestational age by ultrasound, due to size differences, can partially explain currently reported sex differences in early term and late preterm infants' adverse neonatal outcomes, and should be taken into account in clinical decisions and when interpreting study results related to fetal sex.

Place, publisher, year, edition, pages
2016. Vol. 16, article id 335
Keyword [en]
Pregnancy dating, Ultrasound, Gestational age, Antenatal, Infant, Morbidity
National Category
Obstetrics, Gynecology and Reproductive Medicine
Identifiers
URN: urn:nbn:se:uu:diva-308914DOI: 10.1186/s12884-016-1129-zISI: 000386858200001PubMedID: 27799069OAI: oai:DiVA.org:uu-308914DiVA, id: diva2:1051206
Funder
The Karolinska Institutet's Research Foundation
Available from: 2016-12-01 Created: 2016-12-01 Last updated: 2018-03-15Bibliographically approved
In thesis
1. Discrepancy between pregnancy dating methods – correlates and outcomes
Open this publication in new window or tab >>Discrepancy between pregnancy dating methods – correlates and outcomes
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

With the introduction of obstetric ultrasound there has been a shift from last menstrual period-based to ultrasound-based estimation of gestational age. The choice of the method and timing of pregnancy dating is important because it can affect dating precision and perinatal outcomes.

First, when comparing two large population-based cohorts from the Medical Birth Register, from before and after the introduction of ultrasound-based pregnancy dating, male infants on the edge of prematurity did not benefit from progress in medical care as much as female infants in terms of prematurity-related outcomes. This might reflect a bias introduced by the ultrasound-based pregnancy dating method, because of a tendency to overestimate gestational age in pregnancies with a male fetus.

Second, in a large population-based cross-sectional study, the associations of discrepancies between last menstrual period-based and ultrasound-based estimates with variables such as fetal sex and maternal height, indicated that ultrasound-based pregnancy dating introduced systematic errors presumably related to the method’s use of fetal size as a proxy for gestational age. The largest effect estimates were found for maternal obesity in cases of large negative discrepancies.

Third, in a large population-based cohort study, discrepancies between last menstrual period-based and ultrasound-based estimates were associated with several adverse pregnancy, delivery, and neonatal outcomes. Most importantly, a large negative discrepancy was associated with higher odds for neonatal and intrauterine fetal death, as well as for an infant being small for gestational age.

Fourth, in a survey study there was overall good adherence to national guidelines, except for early pregnancy dating. However, the management of discrepancies between methods for pregnancy dating varied widely in clinical practice, which may be due to the lack of national guidelines.

In summary, ultrasound-based dating can be biased by maternal or fetal characteristics. Discrepancies between methods for pregnancy dating may indicate a need for closer monitoring to optimize perinatal care during pregnancy and childbirth.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2018. p. 59
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 1444
Keyword
pregnancy, gestational age, ultrasound, last menstrual period
National Category
Obstetrics, Gynecology and Reproductive Medicine
Research subject
Obstetrics and Gynaecology
Identifiers
urn:nbn:se:uu:diva-345957 (URN)978-91-513-0277-5 (ISBN)
Public defence
2018-05-04, Samlingssalen, Psykiatricentrum, ingång 29, Västmanlands sjukhus, Västerås, 13:15 (Swedish)
Opponent
Supervisors
Available from: 2018-04-11 Created: 2018-03-15 Last updated: 2018-04-19

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