Prior Adverse Pregnancy Outcome and the Risk of Stillbirth

Subsequent risk of stillbirth, preterm birth, and small for gestational age: A cross-outcome analysis of adverse birth outcomes

BACKGROUND

Stillbirth, preterm birth, and small for gestational age (SGA) birth have an increased recurrence risk. The occurrence of one of these biologically related outcomes could also increase the risk for another one of these outcomes in a subsequent pregnancy.

OBJECTIVES

We assessed cross-outcome risks for subsequent stillbirth, preterm birth, and SGA.

METHODS

We used live birth and fetal death records to identify singleton, sequential birth pairs in California (1997-2017). Stillbirth was defined as delivery at ≥20 weeks of gestation of a foetus that died in utero; preterm birth as live birth at 20-36 weeks; and small for gestational age as sex-specific birthweight <10th percentile for gestational age. Risk ratios (RR) were computed using modified Poisson regression and adjusted for potential confounders. Sensitivity analyses included analysing a cohort restricted to primiparous index births and using inverse-probability censoring weights.

RESULTS

Of 3,108,532 birth pairs, 16,668 (0.5%), 260,596 (8.4%) and 331,109 (10.7%) of index births were stillborn, preterm and SGA, respectively. Among individuals with an index stillbirth, the adjusted RRs were 1.90 (95% confidence interval [CI] 1.83, 1.98) for subsequent preterm and 1.35 (95% CI 1.28, 1.41) for subsequent SGA. Among those with index preterm birth, the adjusted RRs were 2.02 (95% CI 1.92, 2.13) for stillbirth and 1.42 (95% CI 1.41, 1.44) for SGA. Among those with index SGA, the adjusted RRs were 1.54 (95% CI 1.46, 1.63) for stillbirth and 1.45 (95% CI 1.44, 1.47) for preterm birth. Similar results were reported for sensitivity analyses.

CONCLUSIONS

Individuals experiencing stillbirth, preterm birth, or SGA in one pregnancy had an increased risk of one of these biologically related outcomes in a subsequent pregnancy. These findings could encourage enhanced surveillance for individuals who experience stillbirth, preterm birth, or SGA and desire a subsequent pregnancy.

The role of confounding in the association between pregnancy complications and subsequent preterm birth: a cohort study

OBJECTIVE

To estimate the degree of confounding necessary to explain the associations between complications in a first pregnancy and the subsequent risk of preterm birth.

DESIGN

Population-based cohort study.

SETTING

Western Australia.

POPULATION

Women (n = 125 473) who gave birth to their first and second singleton children between 1998 and 2015.

MAIN OUTCOME MEASURES

Relative risk (RR) of a subsequent preterm birth (<37 weeks of gestation) with complications of pre-eclampsia, placental abruption, small-for-gestational age and perinatal death (stillbirth and neonatal death within 28 days of birth). We derived e-values to determine the minimum strength of association for an unmeasured confounding factor to explain away an observed association.

RESULTS

Complications in a first pregnancy were associated with an increased risk of a subsequent preterm birth. Relative risks were significantly higher when the complication was recurrent, with the exception of first-term perinatal death. The association with subsequent preterm birth was strongest when pre-eclampsia was recurrent. The risk of subsequent preterm birth with pre-eclampsia was 11.87 (95% CI 9.52-14.79) times higher after a first term birth with pre-eclampsia, and 64.04 (95% CI 53.58-76.55) times higher after a preterm first birth with pre-eclampsia, than an uncomplicated term birth. The e-values were 23.22 and 127.58, respectively.

CONCLUSIONS

The strong associations between recurrent pre-eclampsia, placental abruption and small-for-gestational age with preterm birth supports the hypothesis of shared underlying causes that persist from pregnancy to pregnancy. High e-values suggest that recurrent confounding is unlikely, as any such unmeasured confounding factor would have to be uncharacteristically large.

TWEETABLE ABSTRACT

First pregnancy complications are associated with a higher risk of subsequent preterm birth, with evidence strongest for pregnancies complicated by pre-eclampsia.

Term complications and subsequent risk of preterm birth: registry based study

OBJECTIVE

To explore conditions and outcomes of a first delivery at term that might predict later preterm birth.

DESIGN

Population based, prospective register based study.

SETTING

Medical Birth Registry of Norway, 1999-2015.

PARTICIPANTS

302 192 women giving birth (live or stillbirth) to a second singleton child between 1999 and 2015.

MAIN OUTCOME MEASURES

Main outcome was the relative risk of preterm delivery (<37 gestational weeks) in the birth after a term first birth with pregnancy complications: pre-eclampsia, placental abruption, stillbirth, neonatal death, and small for gestational age.

RESULTS

Women with any of the five complications at term showed a substantially increased risk of preterm delivery in the next pregnancy. The absolute risks for preterm delivery in a second pregnancy were 3.1% with none of the five term complications (8202/265 043), 6.1% after term pre-eclampsia (688/11 225), 7.3% after term placental abruption (41/562), 13.1% after term stillbirth (72/551), 10.0% after term neonatal death (22/219), and 6.7% after term small for gestational age (463/6939). The unadjusted relative risk for preterm birth after term pre-eclampsia was 2.0 (95% confidence interval 1.8 to 2.1), after term placental abruption was 2.3 (1.7 to 3.1), after term stillbirth was 4.2 (3.4 to 5.2), after term neonatal death was 3.2 (2.2 to 4.8), and after term small for gestational age was 2.2 (2.0 to 2.4). On average, the risk of preterm birth was increased 2.0-fold (1.9-fold to 2.1-fold) with one term complication in the first pregnancy, and 3.5-fold (2.9-fold to 4.2-fold) with two or more complications. The associations persisted after excluding recurrence of the specific complication in the second pregnancy. These links between term complications and preterm delivery were also seen in the reverse direction: preterm birth in the first pregnancy predicted complications in second pregnancies delivered at term.

CONCLUSIONS

Pre-eclampsia, placental abruption, stillbirth, neonatal death, or small for gestational age experienced in a first term pregnancy are associated with a substantially increased risk of subsequent preterm delivery. Term complications seem to share important underlying causes with preterm delivery that persist from pregnancy to pregnancy, perhaps related to a mother's predisposition to disorders of placental function.

Risk of stillbirth, preterm delivery, and fetal growth restriction following exposure in a previous birth: systematic review and meta-analysis

BACKGROUND

Little is known about the risk of non-recurrent adverse birth outcomes.

OBJECTIVES

To evaluate the risk of stillbirth, preterm birth (PTB), and small for gestational age (SGA) as a proxy for fetal growth restriction (FGR) following exposure to one or more of these factors in a previous birth.

SEARCH STRATEGY

We searched MEDLINE, EMBASE, Maternity and Infant Care, and Global Health from inception to 30 November 2016.

SELECTION CRITERIA

Studies were included if they investigated the association between stillbirth, PTB, or SGA (as a proxy for FGR) in two subsequent births.

DATA COLLECTION AND ANALYSIS

Meta-analysis and pooled association presented as odds ratios (ORs) and adjusted odds ratios (aORs).

MAIN RESULTS

Of the 3399 studies identified, 17 met the inclusion criteria. A PTB or SGA (as a proxy for FGR) infant increased the risk of subsequent stillbirth ((pooled OR 1.70; 95% confidence interval, 95% CI, 1.34-2.16) and (pooled OR 1.98; 95% CI 1.70-2.31), respectively). A combination of exposures, such as a preterm SGA (as a proxy for FGR) birth, doubled the risk of subsequent stillbirth (pooled OR 4.47; 95% CI 2.58-7.76). The risk of stillbirth also varied with prematurity, increasing three-fold following PTB <34 weeks of gestation (pooled OR 2.98; 95% CI 2.05-4.34) and six-fold following preterm SGA (as a proxy for FGR) <34 weeks of gestation (pooled OR 6.00; 95% CI 3.43-10.49). A previous stillbirth increased the risk of PTB (pooled OR 2.82; 95% CI 2.31-3.45), and subsequent SGA (as a proxy for FGR) (pooled OR 1.39; 95% CI 1.10-1.76).

CONCLUSION

The risk of stillbirth, PTB, or SGA (as a proxy for FGR) was moderately elevated in women who previously experienced a single exposure, but increased between two- and three-fold when two prior adverse outcomes were combined. Clinical guidelines should consider the inter-relationship of stillbirth, PTB, and SGA, and that each condition is an independent risk factor for the other conditions.

TWEETABLE ABSTRACT

Risk of adverse birth outcomes in next pregnancy increases with the combined number of previous adverse events.

PLAIN LANGUAGE SUMMARY

Why and how was the study carried out? Each year, around 2.6 million babies are stillborn, 15 million are born preterm (<37 weeks of gestation), and 32 million are born small for gestational age (less than tenth percentile for weight, smaller than usually expected for the relevant pregnancy stage). Being born preterm or small for gestational age can increase the chance of long-term health problems. The effect of having a stillbirth, preterm birth, or small-for-gestational-age infant in a previous pregnancy on future pregnancy health has not been summarised. We identified 3399 studies of outcomes of previous pregnancies, and 17 were summarised by our study. What were the main findings? The outcome of the previous pregnancy influenced the risk of poor outcomes in the next pregnancy. Babies born to mothers who had a previous preterm birth or small-for-gestational-age birth were more likely to be stillborn. The smaller and the more preterm the previous baby, the higher the risk of stillbirth in the following pregnancy. The risk of stillbirth in the following pregnancy was doubled if the previous baby was born both preterm and small for gestational age. Babies born to mothers who had a previous stillbirth were more likely to be preterm or small for gestational age. What are the limitations of the work? We included a small number of studies, as there are not enough studies in this area (adverse birth outcomes followed by adverse cross outcomes in the next pregnancy). We found very few studies that compared the risk of small for gestational age after preterm birth or stillbirth. Definitions of stillbirth, preterm birth categories, and small for gestational age differed across studies. We did not know the cause of stillbirth for most studies. What are the implications for patients? Women who have a history of poor pregnancy outcomes are at greater risk of poor outcomes in following pregnancies. Health providers should be aware of this risk when treating patients with a history of poor pregnancy outcomes.

Maternal, Labor, Delivery, and Perinatal Outcomes Associated with Placental Abruption: A Systematic Review

Objective Risk factors for placental abruption have changed, but there has not been an updated systematic review investigating outcomes. Methods We searched PubMed, EMBASE, Web of Science, SCOPUS, and CINAHL for publications from January 1, 2005 through December 31, 2016. We reviewed English-language publications reporting estimated incidence and/or risk factors for maternal, labor, delivery, and perinatal outcomes associated with abruption. We excluded case studies, conference abstracts, and studies that lacked a referent/comparison group or did not clearly characterize placental abruption. Results A total of 123 studies were included. Abruption was associated with elevated risk of cesarean delivery, postpartum hemorrhage and transfusion, preterm birth, intrauterine growth restriction or low birth weight, perinatal mortality, and cerebral palsy. Additional maternal outcomes included relaparotomy, hysterectomy, sepsis, amniotic fluid embolism, venous thromboembolism, acute kidney injury, and maternal intensive care unit admission. Additional perinatal outcomes included acidosis, encephalopathy, severe respiratory disorders, necrotizing enterocolitis, acute kidney injury, need for resuscitation, chronic lung disease, infant death, and epilepsy. Conclusion Few studies examined outcomes beyond the initial birth period, but there is evidence that both mother and child are at risk of additional adverse outcomes. There was also considerable variation in, or absence of, the reporting of abruption definitions.

Parity derived for pregnant women using historical administrative hospital data: accuracy varied among patient groups

OBJECTIVES

Understanding patterns of maternity care requires knowing which women have given birth previously, but this information is typically unavailable in administrative hospital data sets. We assessed how well parity can be derived using linked historical records.

STUDY DESIGN AND SETTING

Using Hospital Episode Statistics data, we identified records of women who gave birth between April 2009 and March 2010 in English National Health Service hospitals. The parity coded in these records was compared with an estimate derived from deliveries identified in previous hospital admissions between April 2000 and March 2009.

RESULTS

We identified 358,849 eligible deliveries with complete parity data in the 2009-10 birth records. The historical data classified 168,041 women as multiparous; of whom, 98% were coded as multiparous in their birth record. Among 190,798 women classified as primiparous using historical data, 72% were coded as primiparous in their birth record. The proportion of accurate predictions about primiparous status from historical data varied with age, ranging from 89% for 15-18 year olds to 50% for women aged more than 35 years.

CONCLUSION

Historical records in administrative hospital data sets give accurate information on multiparous status of women. There is some misclassification of primiparous status, and error rates differ among subgroups of women.

Recurrence of perinatal death in Northern Tanzania: a registry based cohort study

Background

Perinatal mortality is known to be high in Sub-Saharan Africa. Some women may carry a particularly high risk which would be reflected in a high recurrence risk. We aim to estimate the recurrence risk of perinatal death using data from a hospital in Northern Tanzania.

Methods

We constructed a cohort study using data from the hospital based KCMC Medical Birth Registry. Women who delivered a singleton for the first time at the hospital between 2000 and 2008 were followed in the registry for subsequent deliveries up to 2010 and 3,909 women were identified with at least one more delivery within the follow-up period. Recurrence risk of perinatal death was estimated in multivariate models analysis while adjusting for confounders and accounting for correlation between births from the same mother.

Results

The recurrence risk of perinatal death for women who had lost a previous baby was 9.1%. This amounted to a relative risk of 3.2 (95% CI: 2.2 - 4.7) compared to the much lower risk of 2.8% for women who had had a surviving baby. Recurrence contributed 21.2% (31/146) of perinatal deaths in subsequent pregnancies. Preeclampsia, placental abruption, placenta previa, induced labor, preterm delivery and low birth weight in a previous delivery with a surviving baby were also associated with increased perinatal mortality in the next pregnancy.

Conclusions

Some women in Tanzanian who suffer a perinatal loss in one pregnancy are at a particularly high risk of also losing the baby of a subsequent pregnancy. Strategies of perinatal death prevention that target pregnant women who are particularly vulnerable or already have experienced a perinatal loss should be considered in future research.

[Risk factors for perinatal mortality in the city of Lubumbashi, Democratic Republic of Congo]

BACKGROUND

The aim of this study is to establish factors explaining perinatal death rates in the city of Lubumbashi.

METHODS

We have carried out a case controlled study in the maternity ward of Jason Sendwe hospital. Perinatal death cases have been compared to those of surviving newborn children among parturient women in the course of 2008. Sociodemographic characteristics, maternal morbidity, children's typical features, have been studied as independent variables. Their effect on perinatal mortality has been assessed using an adjusted odds ratio value at a 5% confidence interval and a logistic regression model.

RESULTS

In total, we considered 2279 births (mother and child pairs) for our study. Among these were 415 perinatal mortality cases and 1864 control cases. After adjustment for several parameters, household chores (AOR=1.8; 95% IC=1.2-2.9), multiple pregnancies (AOR=1.9; 95% IC=1.2-2.9), malaria (AOR=1.4; 95% IC=1.1-1.8), primiparity (AOR=1.7; 95% IC=1.3-2.4), stillbirth (AOR=5.2; 95% IC=2.5-11.0) and prematurity (AOR=2.9; 95% IC=1.5-5.5) in previous pregnancies, onset of antepartum ferver (AOR=3.0; 95% IC=1.2-7.3) and antepartum hemorrhage (AOR=6.8; 95% IC=3.1-15.0), lack of fetal motions near delivering time, dystocias (AOR=2.0; 95% IC=1.3-3.0), low birthweight (AOR=15.7; 95% IC=11.2-22.0), very low birthweight (AOR=49.0; 95% IC=28.6-85.1) and foetal macrosomia (AOR=3.5; 95% IC=1.8-7.0) were the main factors explaining perinatal mortality.

CONCLUSION

Perinatal mortality in Lubumbashi remains associated with several avoidable factors. Basic and emergency obstetrical-neonatal care (B-EMONC) should be improved. Significant efforts should be made in this direction. Perinatal audits should be established for a good heath care quality follow-up. Obstetrical care should be offered as a continuum in order to facilitate communication between the different caregivers.

The preterm birth syndrome: issues to consider in creating a classification system

A comprehensive classification system for preterm birth requires expanded gestational boundaries that recognize the early origins of preterm parturition and emphasize fetal maturity over fetal age. Exclusion of stillbirths, pregnancy terminations, and multifetal gestations prevents comprehensive consideration of the potential causes and presentations of preterm birth. Any step in parturition (cervical softening and ripening, decidual-membrane activation, and/or myometrial contractions) may initiate preterm parturition, and should be recorded for every preterm birth, as should the condition of the mother, fetus, newborn, and placenta, before a phenotype is assigned.

Thrombophilias and stillbirth

It is often postulated that both inherited and acquired thrombophilias increase the risk of stillbirth. In an attempt to reduce this theoretical risk, pregnant patients with prior fetal losses and thrombophilias are anticoagulated. However, there is no definitive proof that thrombophilias are causally linked to stillbirth. Prospective studies have failed to establish a definitive link between inherited thrombophilias and stillbirth. The extant literature suggests that only high concentrations of antiphospholipid antibodies are associated with stillbirth. Moreover, when pregnant women with prior fetal losses even in these cases are placed on anticoagulation, it is unclear that their recurrence risk of stillbirth decreases.