Causes and consequences of recent increases in preterm birth among twins.

OBJECTIVE: To examine the causes and consequences of the recent increase in preterm birth among twins. METHODS: We studied all twin births among residents of the province of Nova Scotia, Canada, between 1988 and 1997. Rates of preterm birth, preterm labor induction, preterm cesarean, small-for-gestational age (SGA), respiratory distress syndrome (RDS), stillbirth, perinatal mortality, and infant mortality were compared between past and more recent years. Changes in perinatal mortality were examined using logistic regression to adjust for the effects of other determinants. RESULTS: The study included 2516 twin births (73 stillbirths and 2443 live births). The rate of preterm birth increased from 42.3% in 1988-1992 to 48.2% of twin live births in 1993-1997 (14% increase, P =.04). Twin live births born after preterm labor induction increased from 3.5% in 1988-1989 to 8.6% in 1996-1997 (P for trend =.007). Of live births between 34 and 36 weeks' gestation, the proportion born SGA decreased from 17.5% in 1988-1992 to 9.2% in 1993-1997 (P =.005). Over the same period, rates of prophylactic maternal steroid therapy increased substantially and rates of RDS declined. Perinatal mortality rates among pregnancies reaching 34 weeks decreased from 12.9 per 1000 total births in 1988-1992 to 4.2 per 1000 total births in 1993-1997 (P =.05). CONCLUSION: Increases in preterm labor induction appear to be responsible for the recent increase in preterm birth among twins. These changes have been accompanied by decreases in perinatal morbidity and mortality among twin pregnancies that reach 34 weeks' gestation.     

Book reviews

In the UK, the live birth rate after IVF in women aged less than 36 is >25%. The multiple birth rates in these women are excessive (20% to 25%). The perinatal mortality rate is increased significantly with IVF twins and triplets (8/1000 singletons, 20/1000 twins and 34/1000 triplets). Multiple pregnancies and births significantly increase the risks to the mother and the children, adversely affect family life and are economically disadvantageous to the couple and the wider community. The elective transfer of a single fresh embryo, followed if necessary by a single thawed embryo, in women at high risk of a multiple birth does not reduce the live birth rate and all but prevents the conception of twins and triplets.     

Towards the elective replacement of a single embryo (eSET) in the United Kingdom

In the UK, the live birth rate after IVF in women aged less than 36 is >25%. The multiple birth rates in these women are excessive (20% to 25%). The perinatal mortality rate is increased significantly with IVF twins and triplets (8/1000 singletons, 20/1000 twins and 34/1000 triplets). Multiple pregnancies and births significantly increase the risks to the mother and the children, adversely affect family life and are economically disadvantageous to the couple and the wider community. The elective transfer of a single fresh embryo, followed if necessary by a single thawed embryo, in women at high risk of a multiple birth does not reduce the live birth rate and all but prevents the conception of twins and triplets.     

Role of vaginal infection in fetal and neonatal mortality

Preterm delivery is the chief problem in obstetrics today and the main determinant of infant mortality and morbidity. Despite the dramatic decrease in infant mortality rate during the past several years, the percentage of preterm (<37 weeks gestation) and low birth weight (LBW) (<2500) rates remain elevated. Approximately 10% of all births are preterm, with a rate of 1-2% of infant born before the end of the 32 weeks of gestation and with a weight <1500 g. Despite the importance of the problem, the majority of preterm live births remain unexplained, and programmatic attempts at reversing the high level of preterm births have not been successful. Numerous studies have linked bacterial vaginosis, chorioamniotitis and endometritis with preterm birth and LBW, especially among African women. The number of preterm live births among African women is twice the one among Caucasians. Bacterial vaginosis is an independent risk factor for preterm and LBW births and the mechanism by which bacterial vaginosis causes the preterm birth of an infant with LBW is unknown. The aim of this article was to underline the importance of the treatment and early identification of vaginal infection, in particular if due to bacterial vaginosis, as it can have a substantial affect on the incidence of preterm delivery with LBW.     

Neonatal outcome of infants born after in vitro fertilization at National Taiwan University Hospital.

BACKGROUND AND PURPOSE: This study compared the neonatal outcome between infants born after in vitro fertilization (IVF) and after natural conception at National Taiwan University Hospital. METHODS: All medical records of women who underwent IVF and gave birth at our hospital from January 1995 to December 1996 were reviewed. The charts of their offspring were also reviewed. We compared the neonatal outcome of infants born after IVF with that of infants born after natural conception. Neonatal outcome was evaluated based on preterm birth, very low birth weight (VLBW), perinatal morbidity, and neonatal mortality. RESULTS: A total of 75 women underwent IVF and gave birth to a total of 100 live newborns and two fetuses with intrauterine death during the 2-year study period. Among these newborns, the prevalence of preterm birth was 28%, of perinatal morbidity was 17%, and of neonatal mortality was 3%, which were significantly higher than those among the 7,736 neonates born after natural conception. However, the rate of VLBW was similar between the two groups. The rate of preterm birth for twin pregnancies were higher than that for singleton pregnancies in both groups. CONCLUSION: This study showed that infants born after IVF had a higher risk of preterm birth and higher perinatal morbidity and neonatal mortality.     

The association of in vitro fertilization and perinatal morbidity

In recent years, there has been increasing concern regarding the safety of in vitro fertilization (IVF) because of the potential health impact on these infants. Multiple pregnancy contributes the vast majority of morbidity associated with IVF and, initially, many thought that adverse outcomes after IVF were solely attributable to the high incidence of twin pregnancies. More recently, multiple studies have suggested that IVF singleton pregnancies may be at increased risk for preterm birth, low birth weight, congenital anomalies, perinatal mortality, and several other pregnancy-related complications compared with unassisted singleton pregnancies. We have focused this review on the increased risk of adverse outcomes in IVF singleton conceptions compared with that of unassisted conceptions. The available evidence evaluating the association between IVF and low birth weight, preterm delivery, placental abruption, preeclampsia, congenital anomalies, and perinatal mortality in singleton pregnancies is summarized. In addition, data reporting an increased risk of congenital and chromosomal anomalies after IVF are presented.     

Preterm birth and neonatal mortality in China in 2011

Objective

To determine the incidence of preterm birth, its regional distribution, and associated neonatal mortality in mainland China.

Methods

In a multicenter, hospital-based investigation of preterm birth, 2011 data were obtained from the seven administrative regions of mainland China. Between one and three subcenters were randomly selected for each administrative region, followed by secondary and tertiary hospitals within the chosen subcenters. Data were obtained from women’s medical records, and obstetric and perinatal events were summarized.

Results

Data for 107 905 deliveries were analyzed, which included 7769 (7.1%) preterm births (occurring between 28 and 37 weeks of pregnancy). The incidence varied among regions. Late preterm birth (between 34 and 37 weeks) accounted for 5495 (70.7%) of preterm births. The neonatal mortality rate was 33 deaths per 1000 live preterm births. Of the 254 neonatal deaths, 147 (57.9%) occurred after very preterm birth (between 28 and 32 weeks). Overall, 4519 (58.2%) preterm births occurred by cesarean.

Conclusion

The distribution of preterm birth across China is unbalanced, and neonatal mortality associated with preterm birth is high.     

Obstetric and perinatal outcome of 1655 ICSI and 3974 IVF singleton and 1102 ICSI and 2901 IVF twin births: a comparative analysis

A total of 3974 IVF and 1655 ICSI singleton births and 2901 IVF and 1102 ICSI twin births were evaluated. Pregnancies after both fresh and frozen transfers were included. IVF and ICSI singleton pregnancies were very similar for most obstetric and perinatal variables. The only significant difference was a higher risk for prematurity (< 37 weeks of amenorrhoea) in IVF pregnancies compared with ICSI pregnancies (12.4 versus 9.2%, OR = 1.39, 95% CI = 1.15-1.70). For twin pregnancies, differences were not statistically different except for a higher incidence of stillbirths in the ICSI group (2.08 versus 1.03%, OR = 2.04, 95% CI = 1.14-3.64). Intrauterine growth retardation with or without pregnancy-induced hypertension was observed more often in the ICSI group. Regression analysis of the data with correction for parity and female age showed similar results for twins. For singletons, this analysis showed similar results with the exception of low birth weight babies (< 2500 g), which were also observed more often in IVF pregnancies (9.6 versus 7.9%, OR = 0.79, CI = 0.65-0.98, P = 0.03). This large case-comparative retrospective analysis showed that the obstetric outcome and perinatal health of IVF and ICSI pregnancies is comparable.     

Pregnancy complications and short-term follow-up of infants born after in vitro fertilization and embryo transfer (IVF/ET).

Two hundred and six pregnancies occurring after in vitro fertilization (IVF) and embryo transfer (ET) during a 7-year period in G?teborg were analysed with respect to pregnancy outcome. The clinical abortion rate was 26%, the rate of ectopic pregnancy was 10%, the rate of ongoing pregnancies beyond 24 weeks was 15%, and the rate of deliveries was 49% (n = 100). The hospital records of 98 women with the 100 deliveries resulting in 131 infants were studied. Multiple pregnancy occurred in 27%, including one quadruplet and two triplet pregnancies. Preterm birth occurred in 30% of all pregnancies and in 20% of singleton pregnancies. Thirty-four percent of the infants had a birth weight of less than 2500 g. The perinatal mortality was 46/1000, as estimated from the 24th week of pregnancy. The incidence of major malformation, 2.3%, was similar to that reported from studies in the general population. The first 100 infants born were followed up for 18 months to 8 years. Long-term sequelae were associated with immaturity and low birth weight. No problems during follow-up were disclosed in children who had had an uneventful neonatal period. It is concluded that IVF pregnancies are an obstetric risk group requiring special attention.     

Is the obstetric outcome of in vitro fertilized singleton gestations different from natural ones? A controlled study

Objective: To determine whether singleton IVF pregnancies carry adverse maternal or fetal outcome when compared with naturally conceived gestations.

Design: An analysis of the obstetric outcome of singleton IVF pregnancies in comparison with matched, naturally conceived singleton controls. Setting: In vitro fertilization unit and obstetric service at a tertiary medical center.

Patient(s): Two hundred sixty consecutive singleton IVF pregnancies and 260 naturally conceived singleton controls matched 1:1 for maternal age, parity, ethnic origin, and location and date of delivery.

Intervention(s): In vitro fertilization-ET.

Main Outcome Measure(s): The rate of antenatal obstetric complications, nonvertex presentation, cesarean section, preterm labor, low birth weight, small and very small for gestational age, neonatal intensive care unit admissions, and perinatal mortality.

Result(s): The rates of most antenatal complications were similar in both groups. Urinary tract infection was the only complication diagnosed significantly more frequently after IVF (7.3% versus 1.2%); however, the rates of severe urinary tract infection necessitating hospitalization were similar. The incidence of nonvertex presentation was also similar. The cesarean section rate was significantly higher among IVF patients (41.9% versus 15.5%). The rates of preterm labor, low birth weight, small and very small for gestational age, neonatal intensive care unit admissions, and perinatal mortality were comparable.

Conclusion(s): When controlling for maternal age, parity, ethnic origin, and location and date of delivery, singleton IVF pregnancies do not carry an increased risk for prematurity, low birth weight, or maternal or fetal complications. Still, these pregnancies are associated with a high rate of cesarean sections.     

Obstetric intervention,stillbirth, and preterm birth

Despite widespread recognition that preventing preterm birth is the most important perinatal challenge facing industrialized countries, preterm birth has increased steadily in recent years. This article examines the relation between trends in preterm birth, preterm labor induction/cesarean delivery, stillbirth, and infant mortality. The recent rise in preterm birth in the United States and Canada has been mainly due to increases in mild preterm birth (34-36 weeks). Live births at 34 to 36 weeks' gestation have increased largely as a consequence of increases in preterm induction and preterm cesarean delivery among women at high risk for adverse pregnancy outcomes. Increased obstetric intervention at 34 to 36 weeks' gestation appears to have led to larger-than-expected temporal declines in stillbirth rates at this gestation. Infant mortality rates have declined overall and also among live births at 34 to 36 weeks' gestation. Obstetric intervention at preterm gestation, when indicated, can prevent stillbirth and reduce infant morbidity and mortality despite the increasing rates of preterm delivery.     

Progestational agents to prevent preterm birth: a meta-analysis of randomized controlled trials

OBJECTIVE: To perform an updated systematic review with meta-analysis to further elucidate the efficacy of progestational agents for the prevention of preterm births in patients at elevated risk. DATA SOURCES: Computerized databases, references in published studies, and textbook chapters in all languages were used to identify randomized controlled trials (RCTs) evaluating the use of progestational agents for the prevention of preterm births in women at elevated risk. METHODS OF STUDY SELECTION: We identified RCTs that compared progestational agents with placebo for patients at risk for preterm birth and evaluated at least one of the following: delivery before 37 weeks of gestation, birth weight less than 2,500 g, threatened preterm labor, respiratory distress syndrome, and perinatal mortality. The primary outcomes assessed were preterm delivery and perinatal mortality. TABULATION, INTEGRATION, AND RESULTS: Ten studies met inclusion criteria for this review. For each study with binary outcomes, an odds ratio (OR) with 95% confidence intervals (CIs) was calculated for selected outcomes. Homogeneity was tested across the studies. Compared with women allocated to receive placebo, those who received progestational agents had lower rates of preterm delivery (26.2% versus 35.9%; OR 0.45, 95% CI 0.25-0.80). Similar results were noted when comparing patients who were specifically treated with 17alpha-hydroxyprogesterone caproate (29.3% versus 40.9%; OR 0.45, 95% CI 0.22-0.93). Additionally, subjects allocated to receive 17alpha-hydroxyprogesterone caproate had lower rates of birth weights less than 2,500 g (OR 0.50, 95% CI 0.36-0.71). No differences in rates of hospital admissions for threatened preterm labor or perinatal mortality were noted for subjects receiving progestational agents in general or for those receiving only 17alpha-hydroxyprogesterone caproate specifically. CONCLUSION: The use of progestational agents and 17alpha-hydroxyprogesterone caproate reduced the incidence of preterm birth and low birth weight newborns.     

Hypertension in Pregnancy - Fetal and Infant Outcome a Cohort Study

The influence of hypertension on fetal outcome was investigated in a cohort study over four years (1981–1984). Hypertension occurred in 7.7% of the 9616 pregnancies. The total number of live born infants was 9654: 746 in conjunction with hypertension and 8908 in conjunction with normotension. All pregnancies were dated by an ultrasound scan in week 17. Antihypertensive treatment with beta-adrenoceptor- blockade was given in 266 patients. No significant differences in fetal, neonatal or perinatal mortality rate were observed between hypertensive and normotensive pregnancies when these mortality rates were studied separately. However, the total fetal and infant mortality was found to be significantly higher in hypertensive pregnancies (19.6/1000) as compared with normotensives (9.5/1000). The highest mortality rates were found in pregnancies complicated by proteinuric hypertension (pre-eclampsia) and chronic hypertension. Mortality in hypertensive pregnancies was mainly confined to preterm birth and birth weight <2500 g; still infants with birth weight %lt;2500g to hypertensives had a non-significantly lower mortality than equally small infants to normotensives. The frequency of hyaline membrane disease (IRDS) in preterm infants was of the similar magnitude in conjunction with hypertension and normotension     

Monoamniotic twin pregnancies: antenatal management and perinatal results of 19 consecutive cases

Objective   To describe the obstetric management and perinatal outcome of antenatally diagnosed monoamniotic twin pregnancies (MATP) in a tertiary level maternity unit.
Setting   Port-Royal Maternity Hospital, Paris, France.
Population   MATP that progressed beyond 22 weeks seen from 1993 to 2001.
Methods   A retrospective chart review of all twin pregnancies. Diagnosis of MATP was made by ultrasonography and confirmed by placental pathology.
Main outcome measure   Perinatal mortality.
Results   Among the 1242 twins pregnancies delivered during the study period, 19 were monoamniotic. Four fetuses (10% of all births) had malformations. Perinatal mortality was high ( n = 12, 32%) because of fetal deaths (nine cases) and very preterm births (three neonatal deaths). No fetal deaths occurred after 29 weeks. Of the 15 women with at least one live fetus before labour, 6 gave birth by vaginal delivery (40%). No obstetric accidents occurred during vaginal deliveries.
Conclusion   Perinatal mortality of MATP is still very high, even with accurate, early antenatal diagnosis, intensified surveillance and delivery provided in a tertiary level hospital. The main causes of perinatal deaths are cord accidents in utero , congenital anomalies and very preterm births.     

Obstetric outcome

Pregnancy outcome after in vitro fertilization (IVF) is influenced by many factors, some specific to IVF pregnancies and others shared with the general obstetric population. These factors include the characteristics of infertile couples and their underlying causes of infertility, the criteria used by IVF programmes for selecting couples for treatment, the techniques of fertilization and embryo transfer, the management of the early stages of pregnancy and the high incidence of multiple pregnancy. In comparing outcomes in different IVF programmes or with naturally conceived pregnancies, careful attention must be given to definitions and to the methods used to diagnose pregnancies. Very few studies of pregnancy outcome after IVF have been published so far. The incidence of ectopic pregnancy and spontaneous abortion seems higher than in natural pregnancies. Multiple pregnancy is common in those programmes electing to transfer more than one embryo into the uterus. In one study, preterm birth and low birthweight were about three times more common than in population-based figures. As a result, higher perinatal mortality would also be expected, but no studies are yet available. The sex ratio and the incidence of major congenital malformations appear similar to natural pregnancies, but there are insufficient data to determine whether the risks of chromosomal abnormalities are altered in IVF pregnancies. Further studies are needed to confirm these preliminary results, to obtain better information about the occurrence of chromosomal abnormalities in spontaneous abortions, and to assess fetal growth. Comparisons of results would be enhanced by international agreement on terminology and definitions for pregnancy losses, particularly those occurring in the early stages of pregnancy. Couples considering in vitro fertilization as an option for treatment of their infertility should be counselled about their overall chances of achieving a pregnancy and live births, as well as about the outcome of these pregnancies.     

Clomiphene Citrate and Pregnancy Outcome

Summary: Data from Australia and elsewhere have shown consistently that adverse perinatal outcomes such as preterm birth and perinatal mortality are more common in pregnancies resulting from assisted conception with IVF and GIFT than normally conceived pregnancies. Factors that may contribute to the excess of poor outcomes include maternal factors, the assisted conception procedures themselves and possibly the influence of drugs used to induce superovulation. This review examines the medical literature describing pregnancies following ovulation induction with one of the drugs used to induce superovulation, clomiphene citrate, and compares their outcomes with Australian IVF and GIFT pregnancy outcomes.
The review shows that whilst some studies have suggested higher rates of ectopic pregnancy, spontaneous abortion and congenital malformations in clomiphene citrate induced pregnancies, the findings are inconsistent and the data are flawed. There are only very poor data available on the incidence of preterm birth. Multiple pregnancy is a well-recognized adverse outcome of clomiphene citrate induced pregnancies. Attempts to improve perinatal outcomes of pregnancies following assisted conception will be helped by a better understanding of the relative contributions of maternal and treatment factors and further studies of pregnancy outcome after ovulation induction are needed.     

Obstetrics and perinatal outcome of adolescent nulliparous pregnant women

OBJECTIVE: To study obstetrics and perinatal outcome in nulliparous teenage singleton pregnancies at a referral teaching hospital in the eastern province of Saudi Arabia. METHOD: All singleton births during 1996-2000 of nulliparous mothers aged < or =17 years at King Fahd University Hospital were reviewed (n = 102) and compared with births of a control group of nulliparous mothers aged 20-24 years who delivered during the same period (n = 102). RESULTS: The incidence of nulliparous teenage pregnancies was 0.8%. As compared with women aged 20-24 years, women of 17 years or less were at higher risk of very preterm birth (p < 0.05). The 5-min Apgar scores were not different between the two groups. Babies born to younger mothers had a significantly lower birth weight than those born to older mothers (p < 0.001); the incidence of a low birth weight (<2,500 g) was significantly lower in the control group (p < 0.04). There were no significant differences in distribution of mode of delivery, admission to the special care baby unit, antenatal complications, cesarean section indications, perinatal mortality rate, and early neonatal complications between the two groups. CONCLUSION: The increase in the very preterm births and the subsequently lower birth weight observed in nulliparous teenage women suggest that the maternal age may be a risk factor for very preterm births and associated long-term hazards.     

An assessment of key aetiological factors associated with preterm birth and perinatal mortality.

The 4 main causes of preterm births in 303 women with consecutive deliveries in Flinders Medical Centre were premature rupture of the membranes (39%), spontaneous preterm labour (22%), pregnancy-induced hypertension (17%) and antepartum haemorrhage (12%). Premature rupture of the membranes occurred with equal frequency in singleton and multiple pregnancies and there was no difference in the frequency of this cause between the pregnancies with live outcomes and those with perinatal deaths. Spontaneous preterm labour was more common in multiple pregnancies (39%) than in singleton pregnancies (22%). One in 3 of the preterm births and 79% of the pregnancies with perinatal deaths occurred at less than 32 weeks' gestation. As it is unlikely that any single obstetric and social intervention will be able to reduce these causes of preterm birth research must continue to find markers to predict premature rupture of the membranes and spontaneous preterm labour.     

Determinants of perinatal mortality in Nigeria

Objective

To determine risk factors for perinatal mortality among hospital-based deliveries in Nigeria.

Methods

The WHO Global Maternal and Perinatal Health Survey was implemented in Nigeria as a first step in establishing a global system for monitoring maternal and perinatal health. Twenty-one health facilities with more than 1000 deliveries annually were selected by a stratified multistage cluster sampling strategy. Information was recorded on all women who delivered and their neonates within a 3-month period.

Results

Overall, there were 9208 deliveries, comprising 8526 live births, 369 fresh stillbirths, 282 macerated stillbirths, 70 early neonatal deaths, and 721 perinatal deaths. The stillbirth and perinatal mortality rates were, respectively, 71 and 78 per 1000 deliveries; the early neonatal death rate was 8 per 1000 live births. Approximately 10% of all newborns weighed less than 2500 g, and 12.3% were born at less than 37 weeks of gestation. Predictors of perinatal mortality were mother's age, lack of prenatal care, unbooked status, prematurity, and birth asphyxia.

Conclusion

The perinatal mortality rate remains unacceptably high in Nigeria. Fresh stillbirth accounted for most perinatal deaths. Interventions to improve the utilization and quality of prenatal care, in addition to the quality of intrapartum care, would considerably reduce perinatal death.     

The night--a dangerous time to be born?

An analysis of perinatal mortality by hour of birth among 10,059 births in Canton Ticino (Switzerland) during the years 1979-1982 showed that fewer births occurred at night than during the day. The variations in number of births by hour of birth were attributed to obstetric practices. The perinatal mortality rate for night-time births was more than twice as high as that for the daytime births (+127%, P less than 0.001) and the rates for night-time births exceeded those for daytime births for 13 of the 19 causes of death examined. A higher proportion of the low and very-low-birthweight babies (less than 2500 g and less than 1500 g) were born at night between 19.00 and 06.59 hours.