Theory of obstetrics: an epidemiologic framework for justifying medically indicated early delivery

Obstetric Intervention and Perinatal Outcomes During the Coronavirus Disease 2019 (COVID-19) Pandemic

OBJECTIVE

To quantify pandemic-related changes in obstetric intervention and perinatal outcomes in the United States.

METHODS

We carried out a retrospective study of all live births and fetal deaths in the United States, 2015-2021, with data obtained from the natality, fetal death, and linked live birth-infant death files of the National Center for Health Statistics. Analyses were carried out among all singletons; singletons of patients with prepregnancy diabetes, prepregnancy hypertension, and hypertensive disorders of pregnancy; and twins. Outcomes of interest included preterm birth, preterm labor induction or preterm cesarean delivery, macrosomia, postterm birth, and perinatal death. Interrupted time series analyses were used to estimate changes in the prepandemic period (January 2015-February 2020), at pandemic onset (March 2020), and in the pandemic period (March 2020-December 2021).

RESULTS

The study population included 26,604,392 live births and 155,214 stillbirths. The prepandemic period was characterized by temporal increases in preterm birth and preterm labor induction or cesarean delivery rates and temporal reductions in macrosomia, postterm birth, and perinatal mortality. Pandemic onset was associated with absolute decreases in preterm birth (decrease of 0.322/100 live births, 95% CI 0.506-0.139) and preterm labor induction or cesarean delivery (decrease of 0.190/100 live births, 95% CI 0.334-0.047) and absolute increases in macrosomia (increase of 0.046/100 live births), postterm birth (increase of 0.015/100 live births), and perinatal death (increase of 0.501/1,000 total births, 95% CI 0.220-0.783). These changes were larger in subpopulations at high risk (eg, among singletons of patients with prepregnancy diabetes). Among singletons of patients with prepregnancy diabetes, pandemic onset was associated with a decrease in preterm birth (decrease of 1.634/100 live births) and preterm labor induction or cesarean delivery (decrease of 1.521/100 live births) and increases in macrosomia (increase of 0.328/100 live births) and perinatal death (increase of 9.840/1,000 total births, 95% CI 3.933-15.75). Most changes were reversed in the months after pandemic onset.

CONCLUSION

The onset of the coronavirus disease 2019 (COVID-19) pandemic was associated with a transient decrease in obstetric intervention (especially preterm labor induction or cesarean delivery) and a transient increase in perinatal mortality.

The Global Pregnancy Collaboration (CoLab) symposium on short- and long-term outcomes in offspring whose mothers had preeclampsia: A scoping review of clinical evidence

Preeclampsia is a maternal syndrome characterized by the new onset of hypertension after 20 weeks of gestation associated with multisystemic complications leading to high maternal and fetal/neonatal morbidity and mortality. However, sequelae of preeclampsia may extend years after pregnancy in both mothers and their children. In addition to the long-term adverse cardiovascular effects of preeclampsia in the mother, observational studies have reported elevated risk of cardiovascular, metabolic, cerebral and cognitive complications in children born from women with preeclampsia. Less clear is whether the association between maternal preeclampsia and offspring sequelae are causal, or to what degree the associations might be driven by fetal factors including impaired growth and the health of its placenta. Our discussion of these complexities in the 2018 Global Pregnancy Collaboration annual meeting prompted us to write this review. We aimed to summarize the evidence of an association between maternal preeclampsia and neurobehavioral developmental disorders in offspring in hopes of generating greater research interest in this important topic.

A Systematic Review on Outcomes of Preterm Small for Gestational Infants Born to Women With Hypertensive Disorders in Pregnancy

There is a lack of knowledge on the intersection between prematurity, small for gestational age, and hypertensive disorders of pregnancy (HDP). Therefore, the aim of this systematic review was to examine the outcomes of preterm infants who were small for gestational age born to women with HDP. Searches were conducted with no date restriction through the final search date of May 13, 2020, in the following databases: PubMed, Web of Science Core Collection, Cumulative Index of Nursing and Allied Health Literature Plus with Full Text (EBSCOhost), and Embase (Elsevier). A total of 6 studies were eligible for this review. The adjusted odds of mortality and necrotizing enterocolitis were significantly lower in the pregnancy-induced hypertension (PIH)/HDP group than in the non-PIH/HDP group. There was no significant difference in the odds of respiratory distress syndrome, bronchopulmonary dysplasia, and intraventricular hemorrhage between PIH/HDP and non-PIH/HDP groups. There was no significant difference between PIH/HDP and non-PIH/HDP groups in cystic periventricular leukomalacia, retinopathy of prematurity, late-onset sepsis, patent ductus arteriosus, length of hospital stays, duration of supplemental oxygen use, duration of mechanical ventilation, and continuous airway pressure. The studies included in this systematic review demonstrated that PIH/HDP is associated with lower infant mortality and necrotizing enterocolitis.

Historical and Recent Changes in Maternal Mortality Due to Hypertensive Disorders in the United States, 1979 to 2018

[Figure: see text].

Bias in comparisons of mortality among very preterm births: A cohort study

BACKGROUND

Several studies of prenatal determinants and neonatal morbidity and mortality among very preterm births have resulted in unexpected and paradoxical findings. We aimed to compare perinatal death rates among cohorts of very preterm births (24-31 weeks) with rates among all births in these groups (≥24 weeks), using births-based and fetuses-at-risk formulations.

METHODS

We conducted a cohort study of singleton live births and stillbirths ≥24 weeks' gestation using population-based data from the United States and Canada (2006-2015). We contrasted rates of perinatal death between women with or without hypertensive disorders, between maternal races, and between births in Canada vs the United States.

RESULTS

Births-based perinatal death rates at 24-31 weeks were lower among hypertensive than among non-hypertensive women (rate ratio [RR] 0.67, 95% CI 0.65-0.68), among Black mothers compared with White mothers (RR 0.94, 95%CI 0.92-0.95) and among births in the United States compared with Canada (RR 0.74, 95%CI 0.71-0.75). However, overall (≥24 weeks) perinatal death rates were higher among births to hypertensive vs non-hypertensive women (RR 2.14, 95%CI 2.10-2.17), Black vs White mothers (RR 1.86, 95%CI 184-1.88;) and births in the United States vs Canada (RR 1.08, 95%CI 1.05-1.10), as were perinatal death rates based on fetuses-at-risk at 24-31 weeks (RR for hypertensive disorders: 2.58, 95%CI 2.53-2.63; RR for Black vs White ethnicity: 2.29, 95%CI 2.25-2.32; RR for United States vs Canada: 1.27, 95%CI 1.22-1.30).

CONCLUSION

Studies of prenatal risk factors and between-centre or between-country comparisons of perinatal mortality bias causal inferences when restricted to truncated cohorts of very preterm births.

The fragile foundations of the extended fetuses-at-risk approach

BACKGROUND

Whether denominators for postnatal outcomes (ascertained after live birth) with a presumed prenatal origin should consist of fetuses or live births remains controversial. Proponents argue that the extended fetuses-at-risk (FAR) approach (a), provides a justification for medically indicated preterm delivery, (b), avoids paradoxical results, and (c), permits quantification of incidence of fetal-infant phenomena, such as "revealed" small for gestational age (SGA)-which, under FAR, rises with advancing gestation.

METHODS

This conceptual paper examines the validity of the above arguments.

RESULTS

As obstetricians induce babies early because of fetal (or maternal) compromise and despite the dangers posed by immaturity, there is no need to modify a paradigm that portrays preterm birth as a powerful risk factor. The FAR approach generally avoids "paradoxical" intersections because FAR rates of postnatal outcomes depend on the birth rate. However, this property, which causes rates of most postnatal outcomes to rise at term, can also lead to risk reversals and other misleading findings. The FAR formulation does not yield the incidence of postnatal conditions but, rather, the incidence of live birth (and survival to diagnosis) of babies with prevalent conditions (and, sometimes, future ones).

CONCLUSIONS

The proposed arguments do not provide adequate support for extending the FAR approach to postnatal outcomes. As only live births can contribute to the numerator of rates, the usefulness and interpretability of FAR measures in this setting are limited.

The cultural construction of preterm birth in the United States

This commentary explores four features of the cultural construction of pregnancy and childbirth in the United States: risk categorization as an aspect of reproductive governance, medicalization, intensive mothering with its implications for gender stratification, and the definition of personhood as beginning at conception. The cultural construction of preterm births (those that end before gestation is complete at about 37 weeks) is interwoven with beliefs about risk in pregnancy. Health risk categories overlap with socially stigmatized characteristics and behaviors, opening sub-groups of women up to intensive surveillance and control. The belief that preterm births are preventable and treatable reinforces medical authority and rationalizes the large allocation of resources to specialty (as opposed to primary) maternal and infant care. Expectations for maternal behavior when preterm birth is threatened and when it occurs reinforce norms of intensive mothering, while the ability to keep preterm infants alive reinforces beliefs about fetal personhood. In these ways, the cultural construction of preterm birth in the U.S. holds the broader construction of pregnancy and childbirth in place by raising the stakes of deviation from norms of reproduction to matters of criminality, death, or serious disability.

Evaluation of a Tennessee statewide initiative to reduce early elective deliveries using quasi-experimental methods

BACKGROUND

Concerted quality improvement (QI) efforts have been taken to discourage the practice of early elective deliveries (EEDs), but few studies have robustly examined the impact of directed QI interventions in reducing EED practices. Using quasi-experimental methods, we sought to evaluate the impact of a statewide QI intervention to reduce the practice of EEDs.

METHODS

Retrospective cohort study of vital records data (2007 to 2013) for all singleton births occurring ≥36 weeks in 66 Tennessee hospitals grouped into three QI cohorts. We used interrupted-time series to estimate the effect of the QI intervention on the likelihood of an EED birth statewide, and by hospital cohort. We compared the distribution of hospital EED percentages pre- and post-intervention. Lastly, we used multivariable logistic regression to estimate the effect of QI interventions on maternal and infant outcomes.

RESULTS

Implementation of the QI intervention was associated with significant declines in likelihood of EEDs immediately following the intervention (odds ratio, OR = 0.72; p < 0.001), but these results varied by hospital cohort. Hospital risk-adjusted EED percentages ranged from 1.6-13.6% in the pre-intervention period, which significantly declined to 2.2-9.6% in the post-intervention period (p < 0.001). The QI intervention was also associated with significant reductions in operative vaginal delivery and perineal laceration, and immediate infant ventilation, but increased NICU admissions.

CONCLUSIONS

A statewide QI intervention to reduce EEDs was associated with modest but significant declines in EEDs beyond concurrent and national trends, and showed mixed results in related infant and maternal outcomes.

Towards a unified perinatal theory: Reconciling the births-based and fetus-at-risk models of perinatal mortality

BACKGROUND

There is a need to reconcile the opposing perspectives of the births-based and fetuses-at-risk models of perinatal mortality and to formulate a coherent and unified perinatal theory.

METHODS

Information on births in the United States from 2004 to 2015 was used to calculate gestational age-specific perinatal death rates for low- and high-risk cohorts. Cubic splines were fitted to the fetuses-at-risk birth and perinatal death rates, and first and second derivatives were estimated. Births-based perinatal death rates, and fetuses-at-risk birth and perinatal death rates and their derivatives, were examined to identify potential inter-relationships.

RESULTS

The rate of change in the birth rate dictated the pattern of births-based perinatal death rates in a triphasic manner: increases in the first derivative of the birth rate at early gestation corresponded with exponential declines in perinatal death rates, the peak in the first derivative presaged the nadir in perinatal death rates, and late gestation declines in the first derivative coincided with an upturn in perinatal death rates. Late gestation increases in the first derivative of the fetuses-at-risk perinatal death rate matched the upturn in births-based perinatal death rates. Differences in birth rate acceleration/deceleration among low- and high-risk cohorts resulted in intersecting perinatal mortality curves.

CONCLUSION

The first derivative of the birth rate links a cohort's fetuses-at-risk perinatal death rate to its births-based perinatal death rate, and cohort-specific differences in birth rate acceleration/deceleration are responsible for the intersecting perinatal mortality curves paradox. This mechanistic explanation unifies extant models of perinatal mortality and provides diverse insights.

Temporal trends in neonatal mortality and morbidity following spontaneous and clinician-initiated preterm birth in Washington State, USA: a population-based study

OBJECTIVE

After a decade of increase, the preterm birth (PTB) rate has declined in the USA since 2006, with the largest decline at late preterm (34-36 weeks). We described concomitant changes in gestational age-specific rates of neonatal mortality and morbidity following spontaneous and clinician-initiated PTB among singleton infants.

DESIGN, SETTING AND PARTICIPANTS

This retrospective population-based study included 754 763 singleton births in Washington State, USA, 2004-2013, using data from birth certificates and hospitalisation records. PTB subtypes included preterm premature rupture of membranes (PPROM), spontaneous onset of labour and clinician-initiated delivery.

OUTCOME MEASURES

The primary outcomes were neonatal mortality and a composite outcome including death or severe neonatal morbidity. Temporal trends in the outcomes and individual morbidities were assessed by PTB subtype. Logistic regression yielded adjusted odds ratios (AOR) per 1 year change in outcome and 95% CI.

RESULTS

The rate of PTB following PPROM and spontaneous labour declined, while clinician-initiated PTB increased (all p<0.01). Overall neonatal mortality remained unchanged (1.3%; AOR 0.99, CI 0.95 to 1.02), though gestational age-specific mortality following clinician-initiated PTB declined at 32-33 weeks (AOR 0.85, CI 0.74 to 0.97) and increased at 34-36 weeks (AOR 1.10, CI 1.01 to 1.20). The overall rate of the composite outcome increased (from 7.9% to 11.9%; AOR 1.06, CI 1.05 to 1.08). Among late preterm infants, combined mortality or severe morbidity increased following PPROM (AOR 1.13, CI 1.08 to 1.18), spontaneous labour (AOR 1.09, CI 1.06 to 1.13) and clinician-initiated delivery (AOR 1.10, CI 1.07 to 1.13). Neonatal sepsis rates increased among all preterm infants (AOR 1.09, CI 1.08 to 1.11).

CONCLUSIONS

Timing of obstetric interventions is associated with infant health outcomes at preterm. The temporal decline in late PTB among singleton infants was associated with increased mortality among late preterm infants born following clinician-initiated delivery and increased combined mortality or severe morbidity among all late preterm infants, mainly due to increased rate of sepsis.

Stillbirth and large for gestational age at birth

Aim: A previous large case-control study had documented association between large for gestational age birth weight and stillbirth. We sought to replicate this novel finding.Methods: Retrospective cohort with nested case-control analyses. The data source was a large Canadian perinatal database. Stillbirth was defined as no signs of life at delivery ≥23-weeks gestation. Small and large for gestational age at birth weights were defined using standard Canadian, American, and ultrasound norms.Results: The study population was comprised of 693,186 live births and 3275 stillbirths. Using population norms, large for gestational age (LGA) at birth was not associated with stillbirth in adjusted analysis (OR 0.57, 95% CI [0.45, 0.71]). A statistically significant interaction between pre-existing diabetes and LGA was observed (OR 2.48, 95% CI [1.20, 5.15]). Further case-control analysis found if ultrasound norms were used and controls were selected by date of delivery then LGA was associated with stillbirth (OR 1.91, 95% CI [1.64-2.22]). However, if controls were matched by gestational age at birth then the association was no longer apparent (OR 0.98, 95% CI [0.85-1.13]).Conclusions: Large for gestational age at birth is not associated with stillbirth in the general population. Previously reported association between LGA and stillbirth was likely an artifact of the sampling strategy. LGA may increase the risk of stillbirth in pregnancies complicated by pre-existing and gestational diabetes.

Neonatal respiratory outcomes in pregnancy induced hypertension: introducing a novel index

Objective: To evaluate short-term respiratory outcomes, mortality and bronchopulmonary dysplasia (BPD) in preterm infants born to mothers with and without pregnancy induced hypertension (PIH).Methods: Exposed infants <33 weeks' gestation were matched to controls in a 1:2 ratio, based on gestation, sex and antenatal steroid exposure in this retrospective cohort study. Primary outcomes were a novel cumulative respiratory index (cRI) (product of mean airway pressure-hours and FiO₂-hours while on invasive ventilation during first 72 hours), mortality and BPD.Results: Seventy-nine exposed infants were matched with 158 controls. cRI was higher in exposed infants (median 1854; IQR 186-13,901) versus controls (median 1359; IQR 210-11,302) but not statistically significant (p = .63). On conditional regression analysis, PIH did not predict cRI (adjusted β = 0.96; 95% CI = 0.79-1.17; p = .712). No association between PIH and mortality (unadjusted odds ratio [OR] = 3.14; 95% CI = 0.76-13.0; p=.11) was identified. PIH was significantly associated with BPD on univariate analysis (OR = 2.29; 95% CI = 1.02-5.17; p=.046), but not after adjustment (aOR = 1.26; 95% CI = 0.38-4.19; p=.7).Conclusions: PIH was not associated with cRI, mortality or BPD in this study. Further validation of cRI and exploration of its relationship with PIH as well as neonatal outcomes is warranted.

Association of Temporal Changes in Gestational Age With Perinatal Mortality in the United States, 2007-2015

Importance

Whether the changing gestational age distribution in the United States since 2005 has affected perinatal mortality remains unknown.

Objective

To examine changes in gestational age distribution and gestational age-specific perinatal mortality.

Design, Setting, and Participants

This retrospective cohort study examined trends in US perinatal mortality by linking live birth and infant death data among more than 35 million singleton births from January 1, 2007, through December 31, 2015.

Exposures

Year of birth and changes in gestational age distribution.

Main Outcomes and Measures

Changes in the proportion of births at gestational ages 20 to 27, 28 to 31, 32 to 33, 34 to 36, 37 to 38, 39 to 40, 41, and 42 to 44 weeks; changes in perinatal mortality (stillbirth at ≥20 weeks, and neonatal deaths at <28 days) rates; and contribution of gestational age changes to perinatal mortality. Trends were estimated from log-linear regression models adjusted for confounders.

Results

Among the 34 236 577 singleton live births during the study period, the proportion of births at all gestational ages declined, except at 39 to 40 weeks, which increased (54.5% in 2007 to 60.2% in 2015). Overall perinatal mortality declined from 9.0 to 8.6 per 1000 births (P < .001). Stillbirths declined from 5.7 to 5.6 per 1000 births (P < .001), and neonatal mortality declined from 3.3 to 3.0 per 1000 births (P < .001). Although the proportion of births at gestational ages 34 to 36, 37 to 38, and 42 to 44 weeks declined, perinatal mortality rates at these gestational ages showed annual adjusted relative increases of 1.0% (95% CI, 0.6%-1.4%), 2.3% (95% CI, 1.9%-2.8%), and 4.2% (95% CI, 1.5%-7.0%), respectively. Neonatal mortality rates at gestational ages 34 to 36 and 37 to 38 weeks showed a relative adjusted annual increase of 0.9% (95% CI, 0.2%-1.6%) and 3.1% (95% CI, 2.1%-4.1%), respectively. Although the proportion of births at gestational age 39 to 40 weeks increased, perinatal mortality showed an annual relative adjusted decline of -1.3% (95% CI, -1.8% to -0.9%). The decline in neonatal mortality rate was largely attributable to changes in the gestational age distribution than to gestational age-specific mortality.

Conclusions and Relevance

Although the proportion of births at gestational age 39 to 40 weeks increased, perinatal mortality at this gestational age declined. This finding may be owing to pregnancies delivered at 39 to 40 weeks that previously would have been unnecessarily delivered earlier, leaving fetuses at higher risk for mortality at other gestational ages.

The fetuses-at-risk approach: survival analysis from a fetal perspective

Several phenomena in contemporary perinatology create challenges for analyzing pregnancy outcomes. These include recent increases in iatrogenic delivery at late preterm and early term gestation, which are incongruent with the belief that stillbirth and neonatal death risks decrease exponentially with advancing gestational age. Perinatal epidemiologists have also puzzled over the paradox of intersecting birthweight-specific and gestational age-specific perinatal mortality curves for decades. For example, neonatal mortality rates among preterm infants of women who smoke are substantially lower than neonatal mortality rates among preterm infants of non-smoking women, whereas the reverse pattern occurs at term gestation. This mortality crossover is observed across several contrasts (for example, women with hypertensive disorders of pregnancy vs. normotensive women, older vs. younger women, twins vs. singletons) and outcomes (stillbirth, neonatal death, sudden infant death syndrome and cerebral palsy), and irrespective of how advancing "maturity" is defined (birthweight or gestational age). One approach proposed to address and explain these unexpected phenomena is the fetuses-at-risk model. This formulation involves a reconceptualization of the denominator for perinatal outcome rates from births to surviving fetuses. In this overview of the fetuses-at-risk model, we discuss the central tenets of the births-based and the fetuses-based formulations. We also describe the extension of the fetuses-at-risk approach to outcomes into and beyond the neonatal period and to a multivariable adaptation. Finally, we provide a substantive context by discussing biological mechanisms underlying the fetuses-at-risk model and contemporary obstetric phenomena that are better understood from that model than from one based on births.

Pregnancy-induced hypertension and neonatal outcomes: a systematic review and meta-analysis

OBJECTIVE

Pregnancy-induced hypertension (PIH) is associated with preterm delivery but its independent impact on neonatal outcomes remains unclear. We sought to systematically review and meta-analyze clinical outcomes of preterm infants <37 weeks' gestation born to mothers with and without PIH.

STUDY DESIGN

Medline, Embase, PsychINFO and CINAHL were searched from January 2000 to October 2016. Studies with low-moderate risk of bias reporting neonatal outcomes based on PIH as primary exposure variable were included. Data were extracted independently by two co-authors.

RESULTS

PIH was associated with lower mortality (3 studies; adjusted odds ratio (aOR) 0.65; 95% confidence interval (CI) 0.54 to 0.79), lower severe retinopathy of prematurity (ROP) (2 studies; aOR 0.83; 0.72 to 0.96) and lower severe brain injury (2 studies; unadjusted OR (uOR) 0.57; 0.49 to 0.66). No association between PIH and short-term respiratory outcomes, bronchopulmonary dysplasia (BPD) or necrotizing enterocolitis (NEC) was identified. In subgroup analysis among infants <29 weeks' gestation, BPD odds were higher (3 studies; aOR 1.15; 1.06 to 1.26), whereas mortality lower (2 studies; aOR 0.73; 0.69 to 0.77). In subgroup analysis limited to severe PIH, odds of mortality (3 studies; uOR 2.36; 1.07 to 5.22) and invasive ventilation (3 studies; uOR 3.26; 1.11 to 9.61) were higher. In subgroup analysis limited to preeclampsia, odds of BPD (3 studies; uOR 1.21; 95% CI:1.03 to 1.43) and NEC were higher (3 studies; uOR 2.79; 95% CI:1.57 to 4.96).

CONCLUSION

PIH was associated with reduced odds of mortality and ROP (all infants), but higher odds for BPD (<29 weeks' gestation). The paradoxical reduction in mortality may be due to survival bias and deserves further exploration in future studies.

Omega-3 Long-Chain Polyunsaturated Fatty Acids and Preeclampsia: Trials Say "No," but Is It the Final Word?

Preeclampsia is a dangerous disorder of pregnancy, defined as hypertension with proteinuria. Its nature remains elusive, and measures of prevention and treatment are limited. Observational studies have suggested that preeclampsia is associated with low intake of omega-3 long-chain polyunsaturated fatty acids (LCPUFA). In recent decades, researchers studied LCPUFA supplementation as a measure to prevent preeclampsia. Most of these trials and later systematic reviews yielded negative results. However, these trials had several important limitations associated with heterogeneity and other issues. Recent research suggests that preeclampsia trials should take into consideration the gender of the fetus (and thus sexual dimorphism of placenta), the positive effect of smoking on preeclampsia prevalence, and the possibility that high doses of LCPUFA mid-term or later may promote the disorder instead of keeping it at bay. In this review, we discuss these issues and future prospects for LCPUFA in preeclampsia research.

Sexual Dimorphism in Adverse Pregnancy Outcomes - A Retrospective Australian Population Study 1981-2011

OBJECTIVES

Sexual inequality starts in utero. The contribution of biological sex to the developmental origins of health and disease is increasingly recognized. The aim of this study was to assess and interpret sexual dimorphisms for three major adverse pregnancy outcomes which affect the health of the neonate, child and potentially adult.

METHODS

Retrospective population-based study of 574,358 South Australian singleton live births during 1981-2011. The incidence of three major adverse pregnancy outcomes [preterm birth (PTB), pregnancy induced hypertensive disorders (PIHD) and gestational diabetes mellitus (GDM)] in relation to fetal sex was compared according to traditional and fetus-at-risk (FAR) approaches.

RESULTS

The traditional approach showed male predominance for PTB [20-24 weeks: Relative Risk (RR) M/F 1.351, 95%-CI 1.274-1.445], spontaneous PTB [25-29 weeks: RR M/F 1.118, 95%-CI 1.044-1.197%], GDM [RR M/F 1.042, 95%-CI 1.011-1.074], overall PIHD [RR M/F 1.053, 95%-CI 1.034-1.072] and PIHD with term birth [RR M/F 1.074, 95%-CI 1.044-1.105]. The FAR approach showed that males were at increased risk for PTB [20-24 weeks: RR M/F 1.273, 95%-CI 1.087-1.490], for spontaneous PTB [25-29 weeks: RR M/F 1.269, 95%-CI 1.143-1.410] and PIHD with term birth [RR M/F 1.074, 95%-CI 1.044-1.105%]. The traditional approach demonstrated female predominance for iatrogenic PTB [25-29 weeks: RR M/F 0.857, 95%-CI 0.780-0.941] and PIHD associated with PTB [25-29 weeks: RR M/F 0.686, 95%-CI 0.581-0.811]. The FAR approach showed that females were at increased risk for PIHD with PTB [25-29 weeks: RR M/F 0.779, 95%-CI 0.648-0.937].

CONCLUSIONS

This study confirms the presence of sexual dimorphisms and presents a coherent framework based on two analytical approaches to assess and interpret the sexual dimorphisms for major adverse pregnancy outcomes. The mechanisms by which these occur remain elusive, but sex differences in placental gene expression and function are likely to play a key role. Further research on sex differences in placental function and maternal adaptation to pregnancy is required to delineate the causal molecular mechanisms in sex-specific pregnancy outcome. Identifying these mechanisms may inform fetal sex specific tailored antenatal and neonatal care.

Implications of Using a Fetuses-at-Risk Approach When Fetuses Are Not at Risk

BACKGROUND

Gestational-age-specific rates of postnatal endpoints are sometimes estimated with denominators based on fetuses-at-risk (FAR), rather than live births. However, as infants can only be included in the numerator after they are born alive, interpretation of such rates is problematic.

METHODS

Using simple algebra it can be shown that, at each gestational week, FAR rates of postnatal endpoints are the product of the conventional risk of outcome among live births and the probability of live birth, which increases from near zero early in gestation to close to one in the final weeks. The consequences of such a pattern of live birth on FAR rates are further illustrated in hypothetical scenarios with known conditions.

RESULTS

FAR rates of postnatal endpoints will generally increase towards the end of pregnancy due to the rising probability of live birth, regardless of the 'true' effect of immaturity on risk. In the presence of an exposure that increases the probability of early birth, the same mechanism will cause FAR rates to be higher in the exposed group, even if the exposure has no effect.

CONCLUSIONS

Gestational-age-specific FAR rates of postnatal outcomes strongly depend on the probability of live birth. Thus, they reflect neither the causal effect of gestational length, nor that of a given exposure. Indeed, if an exposure shortens gestation, FAR rates will be higher in exposed infants even when the exposure has no impact on the outcome under study. These intrinsic limitations should be taken into account when applying FAR analyses to postnatal endpoints.

Risk-scoring systems for predicting preterm birth with the aim of reducing associated adverse outcomes

BACKGROUND

Identification of pregnancies that are higher risk than average is important to allow the possibility of interventions aimed at preventing adverse outcomes like preterm birth. Many scoring systems designed to classify the risk of a number of poor pregnancy outcomes (e.g. perinatal mortality, low birthweight, and preterm birth) have been developed, but they have usually been introduced without evaluation of their utility and validity.

OBJECTIVES

To determine whether the use of a risk-screening tool designed to predict preterm birth (in combination with appropriate consequent interventions) reduces the incidence of preterm birth and very preterm birth, and associated adverse outcomes.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (30 June 2015).

SELECTION CRITERIA

All randomised or quasi-randomised (including cluster-randomised) or controlled clinical trials that compared the incidence of preterm birth between groups that used a risk-scoring instrument to predict preterm birth with those who used an alternative instrument, or no instrument; or that compared the use of the same instrument at different gestations. The reports may have been published in peer reviewed or non-peer reviewed publications, or not published, and written in any language.

DATA COLLECTION AND ANALYSIS

All review authors planned to independently assess for inclusion all the potential studies we identified as a result of the search strategy. However, we did not identify any eligible studies.

MAIN RESULTS

Searching revealed no trials of the use of risk-scoring systems for preventing preterm birth.

AUTHORS' CONCLUSIONS

The role of risk-scoring systems in the prevention of preterm birth is unknown.There is a need for prospective studies that evaluate the use of a risk-screening tool designed to predict preterm birth (in combination with appropriate consequent interventions) to prevent preterm birth, including qualitative and/or quantitative evaluation of their impact on women's well-being. If these prove promising, they should be followed by an adequately powered, well-designed randomised controlled trial.

The association between temporal changes in the use of obstetrical intervention and small-for-gestational age live births

BACKGROUND

The literature attributes secular declines in small-for-gestational age (SGA) live births to changes in maternal smoking and other maternal characteristics. However, there are reasons to believe that the observed reductions in SGA may be a consequence of early delivery following obstetric intervention.

METHODS

We examined temporal trends in obstetrical intervention and SGA among singleton live births in the United States from 1990 to 2010. The modified Kitagawa decomposition, based on the fetuses-at-risk approach, was used to assess the relative contribution of changes in the gestational age distribution and gestational age-specific SGA to overall changes in SGA. Reductions in SGA rates due to a left shift in the gestational age distribution were assumed to primarily reflect increased obstetrical intervention, whereas decreases in overall SGA due to decreases in gestational-age-specific SGA rates were assumed to reflect declines in risk factors.

RESULTS

Temporal trends in SGA followed a non-linear pattern, with substantial declines from 10.1% in 1990-92 to 8.9% in 2002-04, followed by a small increase to 9.1% in 2008-10. Rates of maternal smoking steadily decreased throughout the same time period and changes in SGA rates were more consistent with changes in the gestational age distribution. The modified Kitagawa decomposition analysis also attributed the initial decline in SGA rates to changes in the gestational age distribution.

CONCLUSIONS

Complex temporal pattern in SGA rates cannot be explained by the linear pattern of changes in factors like maternal smoking. Changes in the gestational age distribution are more consistent with the observed secular trends in SGA rates.

Maternal and neonatal outcomes of pregnancy in women with chronic hypertension: a retrospective analysis of a national register

INTRODUCTION

Pregnancies complicated by chronic hypertension are at increased risk of adverse pregnancy outcomes. To assess whether planned early delivery might prevent some of these adverse outcomes, we studied maternal and neonatal outcomes of pregnancy in women with chronic hypertension, including gestational-age-specific outcomes.

MATERIAL AND METHODS

We performed a retrospective, population-based cohort study, using data from the Netherlands Perinatal Register. We included women with chronic hypertension and normotensive controls who delivered a singleton without congenital anomalies in 2002-2007. We calculated crude and adjusted odds ratios (OR) with 95% CI, compared delivery and ongoing pregnancy using moving averages, and used multiple Cox regression to adjust for differences in baseline characteristics and to examine adverse neonatal outcomes across subgroups of hypertensive disorder. Main outcome measures were composite adverse maternal and neonatal outcomes.

RESULTS

We included 3457 (0.3%) women with chronic hypertension and 984 932 normotensive controls. Women with chronic hypertension had adverse maternal outcomes more often (28.7% vs. 6.6%, adjusted OR 5.7, 95% CI 5.3-6.2). Their offspring had an increased rate of neonatal morbidity (17.4% vs. 13.2%, adjusted OR 1.2, 95% CI 1.1-1.4) but not of severe adverse neonatal outcomes (2.5% vs. 2.2%, adjusted OR 0.8, 95% CI 0.6-1.0). The increased risk of adverse maternal outcomes for ongoing pregnancy remained stable around 17% at term. The risk of severe adverse neonatal outcomes for birth was at its lowest between 38 and 40 weeks, mainly in women with iatrogenic onset of delivery.

CONCLUSIONS

Women with chronic hypertension are at increased risk of adverse maternal and neonatal outcomes compared with controls throughout pregnancy, including at term. Our results suggest that the optimal timing of delivery might be between 38 and 40 weeks of gestation, but prospective randomized studies should confirm this.

What is the impact of interventions that prevent fetal mortality on the increase of preterm live births in the State of Sao Paulo, Brazil?

Background

There is a global growing trend of preterm births and a decline trend of fetal deaths. Is there an impact of the decline of fetal mortality on the increase of preterm live births in State of Sao Paulo, Brazil?

Methods

The time trends were evaluated by gestational age through exponential regression analysis. Data analyzed included the fetal mortality ratio, proportion of preterm live births, fertility rate of women 35 years and over, prenatal care, mother's education, multiple births and cesarean section deliveries. A survival analysis was carried out for 2000 and 2010.

Results

Preterm births showed the highest annual increase (3.2 %) in the less than 28 weeks of gestation group and fetal mortality ratio decreased (7.4 %) in the same gestational age group. There was an increase of cesarean section births and it was higher in the < 28 weeks group (6.1 %). There was a decreased annual trend of mothers with inadequate prenatal care (6.1 %) and low education (8.8 %) and an increased trend in multiple births and fertility rates of women of 35 years and over. The variables were highly correlated to which other over time. In 2000, 8.2 % of all pregnancies resulted in preterm births (0.9 % in fetal deaths and 7.3 % in live births). In 2010, the preterm birth increased to 9.4 % (0.8 % were preterm fetal deaths and 8.6 % preterm live births).

Conclusions

The results suggest that 45.2 % could be the maximum contribution of successful interventions to prevent a fetal death on the increase in preterm live births. This increasing trend is also related to changes of the women reproductive profile with the change of the women reproductive profile and access to prenatal care.

Predictors of Childhood Anxiety: A Population-Based Cohort Study

Background

Few studies have explored predictors of early childhood anxiety.

Objective

To determine the prenatal, postnatal, and early life predictors of childhood anxiety by age 5.

Methods

Population-based, provincial administrative data (N = 19,316) from Manitoba, Canada were used to determine the association between demographic, obstetrical, psychosocial, medical, behavioral, and infant factors on childhood anxiety.

Results

Risk factors for childhood anxiety by age 5 included maternal psychological distress from birth to 12 months and 13 months to 5 years post-delivery and an infant 5-minute Apgar score of ≤7. Factors associated with decreased risk included maternal age < 20 years, multiparity, and preterm birth.

Conclusion

Identifying predictors of childhood anxiety is a key step to early detection and prevention. Maternal psychological distress is an early, modifiable risk factor. Future research should aim to disentangle early life influences on childhood anxiety occurring in the prenatal, postnatal, and early childhood periods.

Temporal trends in fetal mortality at and beyond term and induction of labor in Germany 2005-2012: data from German routine perinatal monitoring

PURPOSE

While a variety of factors may play a role in fetal and neonatal deaths, postmaturity as a cause of stillbirth remains a topic of debate. It still is unclear, whether induction of labor at a particular gestational age may prevent fetal deaths.

METHODS

A multidisciplinary working group was granted access to the most recent set of relevant German routine perinatal data, comprising all 5,291,011 hospital births from 2005 to 2012. We analyzed correlations in rates of induction of labor (IOL), perinatal mortality (in particular stillbirths) at different gestational ages, and fetal morbidity. Correlations were tested with Pearson's product-moment analysis (α = 5 %). All computations were performed with SPSS version 22.

RESULTS

Induction rates rose significantly from 16.5 to 21.9 % (r = 0.98; p < 0.001). There were no significant changes in stillbirth rates (0.28-0.35 per 100 births; r = 0.045; p = 0.806). Stillbirth rates 2009-2012 remained stable in all gestational age groups irrespective of induction. Fetal morbidity (one or more ICD-10 codes) rose significantly during 2005-2012. This was true for both children with (from 33 to 37 %, r = 0.784, p < 0.001) and without (from 25 to 31 %, (r = 0.920, p < 0.001) IOL.

CONCLUSIONS

An increase in IOL at term is not associated with a decline in perinatal mortality. Perinatal morbidity increased with and without induction of labor.

Trends in childbirth before 39 weeks' gestation without medical indication

BACKGROUND

There is increasing attention to labor induction and cesarean delivery occurring at 37 0/7-38 6/7 weeks' gestation (early-term) without medical indication.

OBJECTIVE

To measure prevalence, change over time, patient characteristics, and infant outcomes associated with early-term nonindicated births.

RESEARCH DESIGN AND SUBJECTS

Retrospective analysis using linked hospital discharge and birth certificate data for the 7,296,363 uncomplicated births (>37 0/7 wk' gestation) between 1995 and 2009 in 3 states.

MEASURES

Early-term nonindicated birth is calculated using diagnosis codes and birth certificate records. Secondary outcomes included infant prolonged length of stay and respiratory distress.

RESULTS

Across uncomplicated term births, the early-term nonindicated birth rate was 3.18%. After adjustment, the risk of nonindicated birth before 39 0/7 weeks was 86% higher in 2009 than in 1995 [hazard ratio (HR)=1.86; 95% confidence interval (CI), 1.81-1.90], peaking in 2006 (HR=2.03; P<0.001). Factors independently associated with higher odds included maternal age, higher education levels, private health insurance, and delivering at smaller-volume or nonteaching hospitals. Black women had higher risk of nonindicated cesarean birth (HR=1.29; 95% CI, 1.27-1.32), which was associated with greater odds of prolonged length of stay [adjusted odds ratio (AOR)=1.60; 95% CI, 1.57-1.64] and infant respiratory distress (AOR=2.44; 95% CI, 2.37-2.50) compared with births after 38 6/7 weeks. Early-term nonindicated induction was also associated with comparatively greater odds of prolonged length of stay (AOR=1.20; 95% CI, 1.17-1.23).

CONCLUSIONS

Nearly 4% of all uncomplicated births to term infants occurred before 39 0/7 weeks' gestation without medical indication. These births were associated with adverse infant outcomes.

Maternal lipid change in relation to length of gestation: a prospective cohort study with preconception enrollment of women

BACKGROUND/AIMS

We sought to investigate the association between preconception serum lipids and their daily rate of change in relation to length of gestation.

METHODS

In a cohort of 70 women, 61 (87%) became pregnant, resulting in 48 (69%) live births. Serum lipid measurements (in milligrams per deciliter) included total cholesterol, free cholesterol, triglycerides and phospholipids at preconception, upon human chorionic gonadotropin-confirmed pregnancy and following pregnancy loss (<14 weeks) or post partum. Pregnancy outcome (loss, preterm and term delivery) and gestational length were modeled relative to daily rate of change in lipids using multinomial regression and Cox proportional hazards models, respectively, adjusting for body mass index and smoking.

RESULTS

A rate of triglyceride change below the median was associated with an increased risk for pregnancy loss compared with term birth (adjusted odds ratio: 9.02; 95% CI: 1.62-50.30). A rate of triglyceride change of ≤0.01 mg/dl per day versus above the median was associated with a trend for increased risk of pregnancy loss or preterm (<37 weeks) birth (adjusted hazard ratio: 1.77; 95% CI: 0.94-3.33).

CONCLUSION

A low rate of triglyceride change during early pregnancy may be a signal of risk of pregnancy loss or preterm birth. Lipids offer promise for identifying pregnancies at risk for adverse outcomes.

Changes in delivery methods at specialty care hospitals in the United States between 2006 and 2010

OBJECTIVE

Given the increasing rates of labor induction and cesarean delivery, and efforts to reduce early term births, we examined recent trends in methods and timing of delivery.

STUDY DESIGN

We identified delivery methods and medical indications for delivery from administrative hospital discharge data for 231 691 deliveries in 2006 and 213 710 deliveries in 2010 from 47 specialty care member hospitals of the National Perinatal Information Center/Quality Analytic Services. In a subset of 17 hospitals, we examined trends by gestational age.

RESULT

From 2006 to 2010, there was an 11% increase in labor induction and a 6% increase in cesarean delivery, largely due to repeat cesareans. There was a 4 per 100 reduction in early term births (37 to 38 weeks), mostly due to a decline in non-medically indicated interventional deliveries.

CONCLUSION

We report a shift in deliveries at 38 weeks, which we believe may be attributed to efforts to actively limit non-medically indicated early term deliveries.

Obstetrical interventions for term first deliveries in the US

BACKGROUND

Labour induction and caesarean are increasingly done without clinical indication. However, little is known about the prevalence of such interventions, or the characteristics of women who receive them. We used the 2003 revision of the US birth certificates to summarise recorded interventions and to characterise maternal profiles associated with such interventions.

METHODS

We carried out a retrospective study of 2.35 million primiparous women delivering singleton live births at 37-44 weeks in the US from 2005 to 2008. We used the 2003 revision of the birth certificate to define delivery categories: 'indicated' were those with induced labour or pre-labour caesarean for hypertension, diabetes, chorioamnionitis, failed cephalic version at ≥40 weeks, growth restriction (<3rd centile), or post-term (≥42 weeks); those with pre-labour caesarean with breech at ≥39 weeks; or those with caesarean with labour lasting ≥12 h, failed trial of labour, vacuum/forceps extraction, or fetal intolerance to labour. Remaining deliveries with induction/caesarean were classified as 'non-indicated' and all other deliveries 'spontaneous'.

RESULTS

Half of all term first births (50%) were delivered after intervention, and half of interventions were non-indicated (26% of all deliveries). Women with interventions were more likely to deliver on a weekday. Non-indicated interventions were more common among socially advantaged women.

CONCLUSIONS

Nearly a quarter of US term first deliveries had an indicated intervention, and another quarter received intervention without a recorded clinical indication. Both numbers are probably underestimates.

Fetal mortality at and beyond term in singleton pregnancies in Baden-Wuerttemberg/Germany 2004-2009

Objective

To evaluate the risk of intrauterine fetal death (IUFD) in low-risk pregnancies at and beyond term under conditions of fetal monitoring practiced in Baden-Wuerttemberg/Germany (BW).

Methods

We performed a retrospective analysis of 472,843 low-risk singleton pregnancies in BW, using data from the local National Medical Birth registry. The setting of fetal monitoring was uniform during the analyzed time period (2004–2009). We calculated the IUFD rate per 1,000 ongoing pregnancies for each gestational week and compared our results to other published studies using the same calculation scheme.

Results

Our study demonstrates a markedly lower risk of IUFD between 37+0/7 and 42+6/7 weeks of pregnancy when compared with data from Scotland, England, and Sweden collected between 1985 and 1996. When our data were compared to a recently published study from California reporting on deliveries between 1997 and 2006, the risk for IUFD was only significantly lower from 41 weeks onward. The distribution of weekly delivery rates shows a trend to earlier deliveries in weeks 37+0/7 to 39+6/7 for the actual cohorts from California and BW.

Conclusion

In our study, the risk for IUFD in pregnancies going beyond term is remarkably lower than found in studies published about other countries. Our results do not support current guidelines which recommend a routine induction of labor in low risk pregnancies at 41+0/7 weeks of pregnancy.

Determinants of increases in stillbirth rates from 2000 to 2010

BACKGROUND

After decades of decline, stillbirth rates have increased in several industrialized countries in recent years. We examined data from the province of British Columbia, Canada, in an attempt to explain this unexpected phenomenon.

METHODS

We carried out a retrospective population-based cohort study of all births in British Columbia from 2000 to 2010. Outcomes of interest included overall stillbirth rates, birth weight-and gestational age-specific stillbirth rates, rates of spontaneous stillbirths (excluding pregnancy terminations that satisfied the definition of stillbirth [fetal death with a birth weight ≥ 500 g or gestational age at delivery ≥ 20 wk], hereafter referred to as "pregnancy terminations") and rates of congenital anomalies among live-born infants. We used logistic regression to adjust for changes in maternal age, parity, weight before pregnancy and multiple births.

RESULTS

Overall, stillbirth rates increased by 31% (95% confidence interval [CI] 13% to 50%), from 8.08 per 1000 total births in 2000 to 10.55 per 1000 in 2010. The rate of stillbirths with a birth weight of less than 500 g increased significantly (p(trend) = 0.03), whereas the rate of stillbirths with a birth weight of 1000 g or more decreased significantly (p(trend) = 0.009). The rate of spontaneous stillbirths decreased nonsignificantly by 16%, from 5.7 per 1000 total births in 2000 to 4.8 per 1000 in 2010. There was a significant decline of 30% (95% CI 6% to 47%) in the rate of spontaneous stillbirth with a birth weight of 1000 g or more between 2000 and 2010; adjustment for maternal factors did not appreciably change this temporal effect. The prevalence of congenital anomalies among live-born infants decreased significantly, from 5.21 per 100 live births during the first 3 years (2000-02) to 4.77 per 100 during the final 3 years (2008-10).

INTERPRETATION

Increases in pregnancy terminations were responsible for the increases observed in stillbirth rates and were associated with declines in the prevalence of congenital anomalies among live-born infants.

Fetal growth: a review of terms, concepts and issues relevant to obstetrics

The perinatal literature includes several potentially confusing and controversial terms and concepts related to fetal size and growth. This article discusses fetal growth from an obstetric perspective and addresses various issues including the physiologic mechanisms that determine fetal growth trajectories, known risk factors for abnormal fetal growth, diagnostic and prognostic issues related to restricted and excessive growth and temporal trends in fetal growth. Also addressed are distinctions between fetal growth 'standards' and fetal growth 'references', and between fetal growth charts based on estimated fetal weight vs those based on birth weight. Other concepts discussed include the incidence of fetal growth restriction in pregnancy (does the frequency of fetal growth restriction increase or decrease with increasing gestation?), the obstetric implications of studies showing associations between fetal growth and adult chronic illnesses (such as coronary heart disease) and the need for customizing fetal growth standards.

Correlates of the trend of cesarean section rates in twin pregnancies

OBJECTIVE

To examine the population-based trend for cesarean births in twin pregnancies for the last 13 years in Slovenia, and to find correlates for this trend.

METHODS

We evaluated data from the Slovenian national perinatal information system (NPIS) of all twin pairs born at ≥24 weeks during the period 1997-2009 (n=3916 pairs).

RESULTS

We noted a significant and steady increase of about 1.1% cesarean births/year, concomitant with significant increased birth rates at 34-36 weeks, but with a significant decrease over time in neonatal mortality. These trends were neither associated with any particular maternal characteristic nor with increased neonatal morbidity.

CONCLUSIONS

An association exists between an increased cesarean birth rate, increased preterm births at 33-36 weeks and concomitant significantly reduced neonatal mortality in twins.

Educational inequalities in preterm and term small-for-gestational-age birth over time

PURPOSE

Time trends in educational inequalities in small-for-gestational-age (SGA) birth are important to evaluate for policy, especially at preterm gestational ages when morbidity and mortality are typically greater. We evaluated educational inequalities in preterm and term SGA birth over time, accounting for potential bias at preterm gestational ages.

METHODS

Data included 2,204,056 singleton live births from 25 to 43 gestational weeks, 1981 to 2007. We estimated prevalence ratios (PR) and percent prevalence differences (PPD) of preterm and term SGA birth for a continuous education score, accounting for maternal characteristics. Sensitivity analyses included correction for misclassification of preterm SGA status, and use of fetuses-at-risk denominators in regression models.

RESULTS

Although prevalence of SGA birth decreased over time, relative educational inequalities (PRs) persisted for preterm and term cases. PPDs decreased slightly, but more for term than preterm SGA birth. Sensitivity analyses indicated that PRs for education were stronger for preterm than term SGA birth. PPDs were larger for term SGA birth in the first period, but greater for preterm SGA birth in the last period.

CONCLUSIONS

Relative educational inequalities in SGA birth persisted over time. The difference in prevalence between the least and most educated mothers is currently greater for preterm than for term SGA birth.

Risk scoring systems for predicting preterm birth with the aim of reducing associated adverse outcomes

BACKGROUND

Identification of pregnancies that are higher risk than average is important to allow the possibility of interventions aimed at preventing adverse outcomes like preterm birth. Many scoring systems designed to classify the risk of a number of poor pregnancy outcomes (e.g. perinatal mortality, low birthweight, and preterm birth) have been developed, but they have usually been introduced without evaluation of their utility and validity.

OBJECTIVES

To determine whether the use of a risk-screening tool designed to predict preterm birth (in combination with appropriate consequent interventions) reduces the incidence of preterm birth and very preterm birth, and associated adverse outcomes.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (December 2010), CENTRAL (The Cochrane Library 2010, Issue 4), MEDLINE (1966 to 17 December 2010), EMBASE (1974 to 17 December 2010), and CINAHL (1982 to 17 December 2010).

SELECTION CRITERIA

All randomised or quasi-randomised (including cluster-randomised) or controlled clinical trials that compared the incidence of preterm birth between groups that used a risk scoring instrument to predict preterm birth with those who used an alternative instrument, or no instrument; or that compared the use of the same instrument at different gestations. The reports may have been published in peer reviewed or non-peer reviewed publications, or not published, and written in any language.

DATA COLLECTION AND ANALYSIS

All review authors planned to independently assess for inclusion all the potential studies we identified as a result of the search strategy. However, we identified no eligible studies.

MAIN RESULTS

Extensive searching revealed no trials of the use of risk scoring systems to prevent preterm birth.

AUTHORS' CONCLUSIONS

The role of risk scoring systems in the prevention of preterm birth is unknown.There is a need for prospective studies that evaluate the use of a risk-screening tool designed to predict preterm birth (in combination with appropriate consequent interventions) to prevent preterm birth, including qualitative and/or quantitative evaluation of their impact on women's well-being. If these prove promising, they should be followed by an adequately powered, well-designed randomised controlled trial.

[Fetal and neonatal complications related to prolonged pregnancy]

OBJECTIVE

To evaluate fetal and neonatal outcomes related to prolonged pregnancy.

METHODS

This study is based on Pubmed search, Cochrane library and HAS recommendations.

RESULTS

The risk of fetal complications including macrosomia (6 %), oligohydramnios (10 %-15 %), abnormal fetal heart rate pattern and meconium-stained fluid is increased in prolonged pregnancy (≥ 41(+0) weeks). The rate of stillbirth was estimated between 1.6 ‰ and 3.0 ‰ live births according to countries in post-term pregnancies (≥ 42(+0) weeks). The risk of umbilical cord pH less than 7.10, Apgar score at five minutes inferior to 7, ICU admissions and perinatal asphyxia is increased in post-term infants (≥ 42(+0) weeks) compared with term infants. The risk of neurologic complications including neonatal convulsion, hypoxic ischemic encephalopathy, cerebral palsy, developmental deviations and epilepsy in childhood is increased in post-term infants. The risk of meconium aspiration syndrome, neonatal sepsis, and birth trauma including shoulder dystocia and bone fracture is increased in post-term infants. The rate of perinatal mortality increases in post-term infants. The perinatal mortality in post-term infants could be explained by perinatal asphyxia and meconium aspiration syndrome.

CONCLUSIONS

The risk of perinatal complications and mortality are increased in prolonged pregnancy.

What is Behind the Rising Rates of Preterm Birth in the United States?

We review three decades of unsuccessful efforts by public policy-makers in the United States to develop programs to lower the rate of preterm birth. We analyze why these efforts had been unsuccessful. Finally, we will speculate about whether something has changed in the last few years that might finally bend the curve and reverse the trend of a steadily rising preterm birth rate.

Timing of delivery for women with stable placenta previa

Women with placenta previa are at increased risks for complications related to obstetrical hemorrhage and the need for emergent delivery. Some will remain asymptomatic without preterm labor or vaginal bleeding, and thus the clinician must decide when to schedule cesarean delivery in a "stable" patient. Decision-making for the optimal timing of delivery across the late preterm and early-term period requires balancing the probability and severity of maternal hemorrhage at each gestational age versus the probability and severity of neonatal morbidity. On the basis of the limited available data, in women with uncomplicated complete placenta previa, scheduled delivery between 36 and 37 weeks should be considered.

The natural history of pregnancy: diseases of early and late gestation

OBJECTIVE

To identify the disease processes underlying the increasing rate of gestational age-specific perinatal mortality observed under the fetuses-at-risk model.

DESIGN

Retrospective cohort study.

SETTING

USA and Nova Scotia, Canada.

POPULATION

Births in the USA (1995 and 2005) and Nova Scotia, Canada (1988-2007).

METHODS

Incidence rates of perinatal death and serious neonatal morbidity were calculated using the fetuses-at-risk approach (e.g. cumulative incidence of stillbirth during any gestational week per 1000 fetuses at risk of stillbirth).

MAIN OUTCOME MEASURES

Perinatal mortality and serious neonatal morbidity.

RESULTS

Perinatal mortality rates increased with advancing gestation. Rates of bronchopulmonary dysplasia, intraventricular haemorrhage, periventricular leucomalacia and retinopathy of prematurity were highest in early gestation, whereas rates of meconium aspiration syndrome and aspiration pneumonitis were highest at late term and post-term gestation. Respiratory depression (i.e. delay in initiating and maintaining respiration after birth, low 5-minute Apgar score or seizures caused by neonatal encephalopathy) showed an increase from 34 weeks onwards. The increase in perinatal mortality rates at late gestation was congruent with increases in respiratory depression. Other findings included a high incidence of respiratory distress syndrome at late gestation, a nonspecific pattern in the gestational age-specific rates of necrotising enterocolitis and high rates of sudden infant death syndrome at late gestation.

CONCLUSIONS

The natural history of pregnancy is characterised by diseases of early and late gestation, with the latter largely determining patterns of gestational age-specific perinatal mortality. These findings have implications for obstetric theory and provide insight into various contemporary phenomena, including the rise in iatrogenic late preterm birth.

What we have here is a failure to communicate: obstacles to optimal care for preterm birth

Obstetricians and pediatricians share the common goal of a healthy beginning for every baby, mother, and family. This article asserts that miscommunication between the specialties, fostered by separate definitions, metrics, and outcomes, is an impediment to optimal care. Solutions are suggested for improving communication and outcomes.

Stillbirth and neonatal mortality in monochorionic and dichorionic twins: a population-based study

BACKGROUND

Chorionicity is one of the main predictors of higher perinatal mortality in twins. The aim of this large population-based study was to analyse stillbirth and neonatal mortality by cause of death and chorionicity and to quantify the risk of stillbirth by gestational age in dichorionic (DC) and monochorionic (MC) twins.

METHODS

We used data on twin maternities delivered in the North of England from 1998 to 2007 and notified to the Northern Survey of Twin and Multiple Pregnancy. Prospective risk of stillbirth by gestational age at death was calculated using number of stillborn fetuses at or beyond a given gestational period per 1000 fetuses in ongoing pregnancies.

RESULTS

There were 4565 twin maternities (9130 twins) with an overall twinning rate of 14.9 per 1000 maternities. The overall stillbirth and neonatal mortality rates in twins during 1998-2007 were 18.0/1000 births and 23.0/1000 live births, respectively. Stillbirth and neonatal mortality rates were significantly higher in MC than DC twins: 44.4 versus 12.2 per 1000 births [relative risk (RR): 3.6; 95% CI: 2.6-5.1], and 32.4 versus 21.4 per 1000 live births (RR: 1.5; 95% CI: 1.04-2.2), respectively. There was no significant improvement over time in either stillbirth or neonatal mortality rates in either group. The prospective risk of antepartum stillbirth was higher for MC than DC twins at all preterm gestations and the highest risk was before 28 weeks' gestation.

CONCLUSIONS

MC twins have higher rates of stillbirth and neonatal mortality than DC twins, and rates did not improve over 1998-2007. The prospective risk of antepartum stillbirth is much higher for MC twins at all gestational ages.

Cesarean section after induction of labor compared with expectant management: no added risk from gestational week 39

OBJECTIVE

To compare induction of labor and expectant management by gestational week with regard to the need for cesarean section (CS) in labor.

DESIGN

Cohort study.

SETTING

National study based on the Danish Birth Registry.

POPULATION

Aggregated data from 230 528 deliveries from 2004 until mid-year 2009. Women with cesarean section before labor, previous cesarean, preterm birth, breech presentation, multiple pregnancy and specified medical illnesses in pregnancy were excluded.

METHODS

We compared by gestational week nulliparous and parous women who were either induced or had expectant management until later spontaneous or induced labor. For each of five comparisons, we conducted multivariable logistic regression analysis, controlling for body mass index, age, smoking in pregnancy and use of epidural analgesia during labor.

MAIN OUTCOME MEASURE

Rate of CS in labor.

RESULTS

From gestational week 39 and thereafter, there was no difference with regard to CS rates in labor among nulliparous and parous women when comparing women with induced labor and those women who waited for a later labor, either induced or spontaneous. The odds ratios (with confidence intervals) for CS in labor in nulliparous women were 0.99 (0.84-1.17), 1.16 (1.04-1.30), 1.04 (0.94-1.15), 1.00 (0.92-1.10) and 0.97 (0.88-1.07) for weeks 37-41, respectively. For parous women the corresponding figures were 1.72 (1.35-2.20), 1.27 (1.04-1.55), 1.15 (0.95-1.39), 1.18 (0.99-1.40) and 1.07 (0.87-1.32), respectively.

CONCLUSIONS

Induction of labor provides a sound tool when counseling a woman either going past term or presenting with a problem, even if it is not a severe medical illness.

Perinatal outcomes associated with low birth weight in a historical cohort

OBJECTIVE

To identify perinatal outcomes associated with low birth weight (LBW).

METHODS

A retrospective cohort study in a tertiary maternity hospital. Analysis of the database on 43,499 liveborn infants delivered between 1986 and 2004 with low (n = 6,477) and normal (n = 37,467) birth weight. Outcomes associated with LBW were identified through crude and adjusted risk ratio (RR) and 95%CI with bivariate and multivariate analysis. The main outcomes were: onset of labor, mode of delivery, indication for cesarean section; amniotic fluid, fetal heart rate pattern, Apgar score, somatic gestational age, gender and congenital malformation.

RESULTS

LBW infants showed more frequently signs of perinatal compromise such as abnormal amniotic fluid volume (especially olygohydramnios), nonreassuring patterns of fetal heart rate, malformation, lower Apgar scores and lower gestational age at birth. They were associated with a greater risk of labor induction and cesarean delivery, but lower risk of forceps.

CONCLUSION

There was a clear association between LBW and unfavorable perinatal outcomes.