Who is at risk for prolonged and postterm pregnancy?

Department of Obstetrics and Gynecology, University of California, San Francisco, CA, USA.
American journal of obstetrics and gynecology (Impact Factor: 4.7). 05/2009; 200(6):683.e1-5. DOI: 10.1016/j.ajog.2009.02.034
Source: PubMed


The objective of the study was to examine risk factors for postterm (gestational age >or= 42 weeks) or prolonged (gestational age >or= 41 weeks) pregnancy.
We conducted a retrospective cohort study of all term, singleton pregnancies delivered at a mature, managed care organization. The primary outcome measures were the rates of pregnancies greater than 41 or 42 weeks' gestation. Multivariable logistic regression models were used to control for potential confounding and interaction.
Specific risk factors for pregnancy beyond 41 weeks of gestation include obesity (adjusted odds ratio [aOR], 1.26; 95% confidence interval [CI], 1.16-1.37), nulliparity (aOR, 1.46; 95% CI 1.42-1.51), and maternal age 30-39 years (aOR, 1.06; 95% CI, 1.02-1.10) and 40 years or older (aOR, 1.07; 95% CI, 1.02-1.12). Additionally, African American, Latina, and Asian race/ethnicity were all associated with a lower risk of reaching 41 or 42 weeks of gestation.
Our findings suggest that there may be biological differences that underlie the risk for women to progress to 41 or 42 weeks of gestation. In particular, obesity is a modifiable risk factor and could potentially be prevented with prepregnancy or interpregnancy interventions.

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    • "Axmon et al. also reported a significant relationship between longer TTP, and EP and abortion.[7] Our results are similar to those of Henriksen et al.[8] Henriksen et al. also reported the correlation between shorter TTP and increase in the prevalence of multiple pregnancy,[9] but we did not have any case with multiple pregnancy in the current study. "
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    ABSTRACT: Background: Studies have shown significant correlation between time to pregnancy (TTP) and pregnancy outcomes. But understanding of these mechanisms may not be facilitated. The aim of this study was to determine the relation between TTP and pregnancy outcome. Materials and Methods: This study was a case cohort study that was done in Shahid Beheshti Educational Hospital during 2006-2007. Women aged 18-35 years, who had only one pregnancy without using any contraception method before pregnancy and delivered their first child, were enrolled in this study. Thus, 801 women were selected and followed up for pregnancy outcome and TTP until the end of pregnancy. All the participants filled in a special questionnaire. Finally the collected data were entered into computer and analyzed by SPSS ver. 20 software. Results: The frequency distribution of TTP-based pregnancy outcome showed that TTP >48 weeks was higher in normal delivery than in abnormal delivery (5.6% vs. 19.4%). According to Chi-square test, the frequency distribution of pregnancy outcome was related to TTP (P < 0.001). Conclusion: According to the results of this study, there is a significant relationship between TTP and pregnancy outcome, and TTP may lead to unwanted complications such as ectopic pregnancy, preterm labor, and abortion. Thus, all women with a long time of contraception, especially in the rural areas, mast be controlled.
    Full-text · Article · Aug 2014
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    • "Post-term pregnancy is defined by the World Health Organization and the International Federation of Obstetrics and Gynecology as a pregnancy proceeding to and beyond 294 days of gestation i.e. 42 weeks + 0 days [1-3]. The term prolonged pregnancy has commonly been used about pregnancies proceeding to or beyond 287 days of gestation, corresponding to 41 weeks + 0 days [4]. Both conditions have been associated with numerous maternal and neonatal adverse outcomes [4-10]. "
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    ABSTRACT: Background Whether gestational age per se increases perinatal mortality in post-term pregnancy is unclear. We aimed at assessing gestational week specific perinatal mortality in small-for-gestational-age (SGA) and non-SGA term and post-term gestations, and specifically to evaluate whether the relation between post-term gestation and perinatal mortality differed before and after ultrasound was introduced as the standard method of gestational age estimation. Methods A population-based cohort study, using data from the Medical Birth Registry of Norway (MBRN), 1967–2006, was designed. Singleton births at 37 through 44 gestational weeks (n = 1 855 682), excluding preeclampsia, diabetes and fetal anomalies, were included. Odds ratios (OR) with 95% confidence intervals (CI) for perinatal mortality and stillbirth in SGA and non-SGA births by gestational week were calculated. Results SGA infants judged post-term by LMP had significantly higher perinatal mortality than post-term non-SGA infants at 40 weeks, independent of time period (highest during 1999–2006 [OR 9.8, 95% CI: 5.7-17.0]). When comparing years before (1967–1986) versus after (1987–2006) ultrasound was introduced, there was no decrease in the excess mortality for post-term SGA versus non-SGA births (ORs from 6.1 [95% CI: 5.2-7.1] to 6.7 [5.2-8.5]), while mortality at 40 weeks decreased significantly (ORs from 4.6, [4.0-5.3] to 3.2 [2.5-3.9]). When assessing stillbirth risk (1999–2006), more than 40% of SGA stillbirths (11/26) judged to be ≥41 weeks by LMP were shifted to lower gestational ages using ultrasound estimation. Conclusions Mortality risk in post-term infants was strongly associated with growth restriction. Such infants may erroneously be judged younger than they are when using ultrasound estimation, so that the routine assessment for fetal wellbeing in the prolonged gestation may be given too late.
    Full-text · Article · May 2014 · BMC Pregnancy and Childbirth
    • "It is, however, known that the overall median pregnancy length with spontaneous onset of labor among African and Asian women is 1 week shorter when compared to white women [3] . White women are more likely to deliver beyond 41 weeks of gestation [4] [6] [17] . Fetal maturation occurs earlier among black and (South) Asian women [17] . "
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    ABSTRACT: Objective: To evaluate whether maternal ethnicity affects perinatal mortality by week of gestation from 39 weeks onwards. Study design: In this cohort study, we used data from the nationwide Netherlands Perinatal Registry from 1999 until 2008. All singleton infants born between 39+0 and 42+6 weeks of gestation without congenital anomalies were included. We used crude and multivariate logistic regression analyses with white Europeans as the reference to calculate the adjusted odds ratios (aOR) of South Asian, African and Mediterranean women. The main outcome measure was perinatal mortality (antepartum and intrapartum/neonatal mortality within 7 days after birth). Results: We studied 1,092,255 singleton deliveries. Perinatal mortality occurred in 2315 infants (2.1‰). There was interaction between gestational age and ethnicity (P<0.0001). In week 40 (40+0-40+6) South Asian (aOR 1.9; 95% CI 1.1-3.4) and Mediterranean (aOR 1.3; 95% CI 1.04-1.7) women had an increased risk of perinatal mortality. The perinatal mortality risk became greater in week 41 for South Asian (aOR 4.5 95% CI 2.8-7.2), African (aOR 2.2; 95%CI 1.4-3.4) and Mediterranean (aOR 2.2; 95% CI 1.8-2.9) women, especially among small for gestational age infants. Conclusion: With increasing gestational age beyond 39 weeks, perinatal mortality risk increases more strongly among South Asian, African and Mediterranean women compared to European whites.
    No preview · Article · Jan 2013 · Journal of Perinatal Medicine
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