Yang, H., Kramer, M. S., Platt, R. W., Blondel, B., Bréart, G., Morin, I., Wilkins, R., & Usher, R. (2002). How does early ultrasound scan estimation of gestational age lead to higher rates of preterm birth? American Journal of Obstetrics and Gynecology, 186(3), 433-437. https://doi.org/10.1067/mob.2002.120487
Yang H, Kramer MS, Platt RW, Blondel B, Bréart G, Morin I, Wilkins R, Usher R. How does early ultrasound scan estimation of gestational age lead to higher rates of preterm birth? Am J Obstet Gynecol. 2002;186(3):433-437. doi:10.1067/mob.2002.120487
Yang, H., et al. "How does early ultrasound scan estimation of gestational age lead to higher rates of preterm birth?" American Journal of Obstetrics and Gynecology, vol. 186, no. 3, 2002, pp. 433-437.
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Department of Pediatrics, McGill University Faculty of Medicine, Montreal, Quebec, Canada.02w6r0892
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Abstract
Objective
Early ultrasound scanning estimation of gestational age is known to increase the reported preterm delivery rate (<37 completed weeks) compared with estimation by date of the last normal menstrual period, but it is unclear how this systematic difference arises.
Study Design
This study was a hospital-based study of 44,623 women who delivered a live-born or stillborn infant between January 1, 1978, and March 31, 1996, and who had both last normal menstrual period-based and early (usually at 16-18 weeks) ultrasound scan-based gestational age estimates. Cross-classification of the 2 estimates by completed weeks was used to examine the direction and magnitude of the differences between them and to compare the resulting classifications of preterm birth.
Results
The early ultrasound scan-based gestational age distribution was shifted uniformly to the left (ie, lower gestational age) relative to the last normal menstrual period gestational age distribution; the early ultrasound scan-based preterm delivery rate was 9.1%, which was 19.5% (n = 659 births) higher than the 7.6% rate by last normal menstrual period (P <.0001). The last normal menstrual period estimate exceeded the early ultrasound scan estimate far more often than the reverse, up to and including early ultrasound scan estimates of 40 weeks. No concentration of 4-week discrepancies was observed in either direction, as would be expected with random or systematic errors in recall of the last normal menstrual period. The absolute number of births at 37 to 39 weeks of gestation (by last normal menstrual period) that were reclassified as preterm (n = 1206 births) was much higher than the number of preterm births at 34 to 36 weeks of gestation that were reclassified as term (n = 581 births). The net increase of 625 preterm births (from 581 to 1206 births) that resulted from reclassification of births at 37 to 39 last normal menstrual period weeks accounted for 95% of the total 659-birth increase in early ultrasound scan-based preterm births at all last normal menstrual period gestational ages.
Conclusion
Early ultrasound scanning reduces the gestational age estimate across the entire gestational age range; early ultrasound scan-based reclassification of gestational age results in a substantial increase in the prevalence of preterm births. Small downward reclassifications exceed upward reclassifications of similar magnitude, which is consistent with previous reports that delayed (>14 days) ovulation is more frequent than early (<14 days) ovulation.
Giménez MC et al., 2023·Biology (Basel)·Free full text on PubMed Central
Modern urban human activities are largely restricted to the indoors, deprived of direct sunlight containing visible and near-infrared (NIR) wavelengths at high irradiance levels. Therapeutic exposure to doses of red and NIR, known as photobiomodulation (PBM), has been effective for a broad range of conditions. In a double-blind, randomized, placebo-controlled study, we aimed to assess the effects of a PBM home set-up on various aspects of well-being, health, sleep, and circadian rhythms in healthy human subjects with mild sleep complaints. The effects of three NIR light (850 nm) doses (1, 4, or 6.5 J·cm(-2)) were examined against the placebo. Exposure was presented five days per week between 9:30 am and 12:30 pm for four consecutive weeks. The study was conducted in both summer and winter to include seasonal variation. The results showed PBM treatment only at 6.5 J·cm(-2) to have consistent positive benefits on well-being and health, specifically improving mood, reducing drowsiness, reducing IFN-γ, and resting heart rate. This was only observed in winter. No significant effects on sleep or circadian rhythms were noted. This study provides further evidence that adequate exposure to NIR, especially during low sunlight conditions, such as in the winter, can be beneficial for human health and wellness.
Chen C et al., 2017·Nat Commun·Free full text on PubMed Central
Reports on bacteria detected in maternal fluids during pregnancy are typically associated with adverse consequences, and whether the female reproductive tract harbours distinct microbial communities beyond the vagina has been a matter of debate. Here we systematically sample the microbiota within the female reproductive tract in 110 women of reproductive age, and examine the nature of colonisation by 16S rRNA gene amplicon sequencing and cultivation. We find distinct microbial communities in cervical canal, uterus, fallopian tubes and peritoneal fluid, differing from that of the vagina. The results reflect a microbiota continuum along the female reproductive tract, indicative of a non-sterile environment. We also identify microbial taxa and potential functions that correlate with the menstrual cycle or are over-represented in subjects with adenomyosis or infertility due to endometriosis. The study provides insight into the nature of the vagino-uterine microbiome, and suggests that surveying the vaginal or cervical microbiota might be useful for detection of common diseases in the upper reproductive tract.Whether the female reproductive tract harbours distinct microbiomes beyond the vagina has been a matter of debate. Here, the authors show a subject-specific continuity in microbial communities at six sites along the female reproductive tract, indicative of a non-sterile environment.
The World Health Organization defines preterm birth as birth at less than 37 completed gestational weeks, but most studies have focused on very preterm infants (birth at <32 weeks) because of their high risk of mortality and serious morbidity. However, infants born at 32 through 36 weeks are more common and their public health impact has not been well studied. To assess the quantitative contribution of mild (birth at 34-36 gestational weeks) and moderate (birth at 32-33 gestational weeks) preterm birth to infant mortality. DESIGN, SETTING, Population-based cohort study using linked singleton live birth-infant death cohort files for US birth cohorts for 1985 and 1995 and Canadian birth cohorts (excluding Ontario) for 1985-1987 and 1992-1994. Relative risks (RRs) and etiologic fractions (EFs) for overall and cause-specific early neonatal (age 0-6 days), late neonatal (age 7-27 days), postneonatal (age 28-364 days), and total infant death among mild and moderate preterm births vs term births (at >/=37 gestational weeks). Relative risks for infant death from all causes among singletons born at 32 through 33 gestational weeks were 6.6 (95% confidence interval [CI], 6.1-7.0) in the United States in 1995 and 15.2 (95% CI, 13.2-17.5) in Canada in 1992-1994; among singletons born at 34 through 36 gestational weeks, the RRs were 2.9 (95% CI, 2.8-3.0) and 4.5 (95% CI, 4.0-5.0), respectively. Corresponding EFs were 3.2% and 4.8%, respectively, at 32 through 33 gestational weeks and 6.3% and 8.0%, respectively, at 34 through 36 gestational weeks; the sum of the EFs for births at 32 through 33 and 34 through 36 gestational weeks exceeded those for births at 28 through 31 gestational weeks. Substantial RRs were observed overall for the neonatal (eg, for early neonatal deaths, 14.6 and 33.0 for US and Canadian infants, respectively, born at 32-33 gestational weeks; EFs, 3.6% and and 6. 2% for US and Canadian infants, respectively) and postneonatal (RRs, 2.1-3.8 and 3.0-7.0 for US and Canadian infants, respectively, born at 32-36 gestational weeks; EFs, 2.7%-5.8% and 3.0%-7.0% for the same groups, respectively) periods and for death due to asphyxia, infection, sudden infant death syndrome, and external causes. Except for a reduction in the RR and EF for neonatal mortality due to infection, the patterns have changed little since 1985 in either country. Mild- and moderate-preterm birth infants are at high RR for death during infancy and are responsible for an important fraction of infant deaths. JAMA. 2000;284:843-849
Measurement and Statistics · Instrument Development and Validation
Despite recognition that estimation of gestational age (GA) based on maternal recollection of the last normal menstrual period (LNMP) is fraught with error, it is not generally appreciated that the magnitude and direction of this error vary as a function of the LNMP estimate. Early second-trimester (16 to 18 weeks) ultrasound determinations of the fetal biparietal diameter were used as the "gold standard" to test the validity of LNMP-based GA estimates in 11,045 women. The large majority of deliveries occurring at or near term showed LNMP estimates that were valid within plus or minus seven days of the ultrasound estimate. As the LNMP GA deviated progressively toward earlier or later GAs, however, the discrepancies became quite marked, especially for postterm dates. The positive predictive values of the LNMP GA estimates decreased dramatically from term (.949) to preterm (.775) to postterm (.119) deliveries. These systematic errors in menstrual GA estimates have profound implications for unnecessary induction, dysfunctional labor and cesarean section, and resultant neonatal and maternal morbidity.
Related research
Pregnancy Complications · Premature Rupture of Membranes
To estimate the risk of adverse outcomes in women whose first day of the last menstrual period (LMP) was unreliable. Among 20,244 singleton pregnancies with measurements of biparietal diameter between 12 and 22 weeks' gestation, LMP was registered as unreliable in 3775 (18.6%) and reliable in 16,469 (81.4%). Adverse outcomes were defined as spontaneous or missed abortions after 12 weeks' gestation, stillbirth or postnatal death within 1 year, preterm birth, birth weight less than 2500 g, and low birth weight (LBW) for gestation (lower than 22% below sex-specific expected weight). Logistic regression analysis and Kaplan-Meier survival analysis were used to analyze the risk of adverse outcomes. The risk of death was doubled in pregnant women with unreliable LMPs compared with those with reliable LMPs (odds ratio [OR] 2.0; 95% confidence interval [CI] 1.5, 2.6). This risk was highest with respect to stillbirth (OR 2.7; 95% CI 1.7, 4.3). The risks of preterm birth, LBW, and LBW for gestation were also significantly increased (ORs 1.5, 1.4, and 1.2; 95% CIs 1.3, 1.7; 1.2, 1.6; and 1. 0, 1.4, respectively). An unreliable LMP is associated with increased risk of adverse outcomes, especially fetal death.
Although shortened cervical length has been consistently associated with spontaneous preterm birth, it is not known when in gestation this risk factor becomes apparent. To determine whether sonographic cervical findings between 16 weeks' and 18 weeks 6 days' gestation predict spontaneous preterm birth and whether serial evaluations up to 23 weeks 6 days' gestation improve prediction in high-risk women. DESIGN, SETTING, Blinded observational study performed between March 1997 and November 1999 at 9 university-affiliated medical centers in the United States in 183 women with singleton gestations who previously had experienced a spontaneous birth before 32 weeks' gestation. Certified sonologists performed 590 endovaginal sonographic examinations at 2-week intervals. Cervical length was measured from the external os to the functional internal os along a closed endocervical canal. Funneling and dynamic cervical shortening were also recorded. Spontaneous preterm birth before 35 weeks' gestation, analyzed by selected cutoff values of cervical length. Forty-eight women (26%) experienced spontaneous preterm birth before 35 weeks' gestation. A cervical length of less than 25 mm at the initial sonographic examination was associated with a relative risk (RR) for spontaneous preterm birth of 3.3 (95% confidence interval [CI], 2.1-5.0; sensitivity = 19%; specificity = 98%; positive predictive value = 75%). After controlling for cervical length, neither funneling (P =.24) nor dynamic shortening (P =.054) were significant independent predictors of spontaneous preterm birth. However, using the shortest ever observed cervical length on serial evaluations, after any dynamic shortening, the RR of a cervical length of less than 25 mm for spontaneous preterm birth increased to 4.5 (95% CI, 2.7-7.6; sensitivity = 69%; specificity = 80%; positive predictive value = 55%). Compared with a single cervical measurement at 16 weeks' to 18 weeks 6 days' gestation, serial measurements at up to 23 weeks 6 days significantly improved the prediction of spontaneous preterm birth in a receiver operating characteristic curve analysis (P =.03). Cervical length assessed by endovaginal sonography between 16 weeks' and 18 weeks 6 days' gestation, augmented by serial evaluations, predicts spontaneous preterm birth before 35 weeks' gestation in high-risk women.
To test whether subfertile women may be at higher risk of preterm delivery. We used data from two population-based cohort studies on risk factors and pregnancy outcome for approximately 20,000 deliveries in three major Danish obstetric departments. The Aalborg-Odense study comprised all pregnant women attending routine antenatal care at two obstetric departments from 1984 to 1987. In all, 11,850 women (86%) filled in a questionnaire at about 36 weeks' gestation. The Aarhus study addressed women at the routine visit near 16 weeks' gestation from 1989 to 1991; a study questionnaire was returned by 6857 (80%). Both studies excluded women with chronic illnesses, multiple fetuses, and inability to speak Danish. Only women with planned pregnancies were included in the analysis. In all, 8855 and 3985 women from Aalborg-Odense and Aarhus, respectively, were eligible for the analyses. In both cohorts, women were categorized according to their waiting time to pregnancy (0-6 months, 7-12 months, and greater than 1 year) and according to examination or treatment for infertility (yes, no). Preterm delivery was defined as birth before 37 completed weeks. Compared with women who tried for 6 months or less before they conceived, women who tried for 7-12 months had 1.3 times (95% confidence interval [CI] 0.8, 2.1) the adjusted risk of preterm delivery in both cohorts, and women with a time to pregnancy of greater than 12 months had adjusted relative risks for preterm delivery of 1.6 (95% CI 1.1, 2.2) for Aalborg-Odense and 1.7 (95% CI 1.1, 2.6) for Aarhus. The results remained similar after excluding women with infertility treatment. Pregnant women with subfertility and clinically defined infertility are more prone to preterm delivery, even in the absence of infertility treatment.
To investigate the relationship between prematurity and birth defects. In a population-based cohort study, infants with birth defects were ascertained through the Metropolitan Atlanta Congenital Defects Program, a surveillance system with active methods of ascertainment. Gestational age data were obtained from birth certificates of liveborn, singleton infants with and without birth defects born in the 5-county metropolitan Atlanta area. Among 264,392 infants with known gestational ages born between 1989 and 1995, 7738 were identified as having birth defects (2.93%). Premature infants (<37 weeks' gestation) were more than two times as likely to have birth defects than term infants (37-41 weeks) (risk ratio = 2.43; 95% CI 2.30-2.56). This relationship was evident for several categories of birth defects. The rate of birth defects varied by gestational age categories, with the highest risk in the 29- to 32-week gestational age category (risk ratio = 3.37). The risk for birth defects is increased in premature infants. Awareness of this relationship is important for clinicians caring for premature infants. The morbidity and mortality associated with a particular defect may be significantly altered by the presence of prematurity. Further study of this association may provide insight into the etiology of these relatively common problems.
Pregnancy › Preterm Birth › Prediction · Research Methods › Measurement and Statistics › Bias and Confounding
Huanming Yang, Michael S Kramer, Robert W Platt, Béatrice Blondel, Gérard Bréart, Isabelle Morin, Robert Usher, Russell Wilkins
H Yang, Mike Kramer, M Kramer, Bob Platt, Rob Platt, Bobby Platt, R Platt, B Blondel, G Bréart, I Morin, Bob Usher, Rob Usher, Bobby Usher, R Usher, R Wilkins
PMID 11904603 11904603 DOI 10.1067/mob.2002.120487 10.1067/mob.2002.120487 Yang et al. 2002, Yang 2002
Cite this article
Yang, H., Kramer, M. S., Platt, R. W., Blondel, B., Bréart, G., Morin, I., Wilkins, R., & Usher, R. (2002). How does early ultrasound scan estimation of gestational age lead to higher rates of preterm birth? American Journal of Obstetrics and Gynecology, 186(3), 433-437. https://doi.org/10.1067/mob.2002.120487
Yang H, Kramer MS, Platt RW, Blondel B, Bréart G, Morin I, Wilkins R, Usher R. How does early ultrasound scan estimation of gestational age lead to higher rates of preterm birth? Am J Obstet Gynecol. 2002;186(3):433-437. doi:10.1067/mob.2002.120487
Yang, H., et al. "How does early ultrasound scan estimation of gestational age lead to higher rates of preterm birth?" American Journal of Obstetrics and Gynecology, vol. 186, no. 3, 2002, pp. 433-437.
