Are preterm black infants larger than preterm white infants, or are they more misclassified?

In birth certificate data for Massachusetts resident births from 1978 to 1982, 12-27% of births purportedly under 31 weeks of gestation were probably misclassified, i.e. had birthweight greater than or equal to 2500 g. Correcting for maldistribution of births removed 34% and 23%, respectively, of black and white births with reported gestational ages less than 36 weeks but with implausible weights. Percentages of unknown and incomplete reports of last menstrual period were also significantly higher for blacks. After adjustment, preterm black infants weighed less than whites at each gestational age. The proportion of infants less than 2500 g born at term (greater than or equal to 37 weeks gestation) was higher (although not significantly) among blacks. These findings are consistent with hypotheses that low socioeconomic status negatively affects the rate of intrauterine growth.     

Postnatal triiodothyronine replacement and respiratory distress syndrome of the preterm infant

Improvements in the management of respiratory distress syndrome (RDS) include pre- and postnatal stimulation of pulmonary maturity, and triiodothyronine (T3) is believed to influence directly surfactant production. Its circulating levels are low in premature infants with RDS probably due to a low thyroxine T4-T3 hepatic conversion mechanism. While a state of hypotriiodothyroninemia exists at birth, we studied the influence of postnatal intravenous T3 administration on the course of RDS in preterm infants of less than 32 weeks' gestation. Fifty preterm infants with RDS were studied (mean gestational age 30.4 +/- 1.2 weeks and birth weight 1,180 +/- 220 g). They were at random assigned to treatment with 50 micrograms L-T3 (Thyrotardin) or to the control group. Mortality rate, peak oxygen concentrations, duration of artificial ventilation and development of major complications of RDS were the criteria to estimate the influence of T3 treatment on RDS. We failed to detect a statistically significant difference between the two groups in all of the mentioned criteria except for FiO2 concentrations required to maintain PaO2 between 50 and 60 mm Hg (p less than 0.05). These observations suggest a relative beneficial effect of T3 replacement on the course of RDS in preterm infants of less than 32 weeks of gestation.     

深度水解蛋白配方奶在不同体重早产儿喂养中的临床效果观察

目的:评估深度水解配方奶(eHPF)在不同体重早产儿早期喂养中临床应用效果。方法:选取2017年9月至2018年12月出生的早产儿,分为极低出生体重儿组(体重1000-1500g之间)62例和低出生体重儿(体重1500-2000g之间)100例,每组再随机分为两组,分别予以深度水解蛋白奶(eHPF)和早产儿配方奶(SPF)喂养。极低出生体重儿组于12小时后开始微量喂养,低出生体重儿12小时内适量喂养;极低出生体重儿组深度水解蛋白奶喂养2周后改早产儿奶喂养,低出生体重儿组深度水解蛋白奶1周后改早产儿奶喂养。比较深度水解蛋白奶在不同体重早产儿早期喂养中的临床应用效果,不同体重早产儿恢复出生体重时间、每日体重增长速度、胃管留置时间、完全肠内喂养天数、住院天数、喂养不耐受发生率、宫外发育迟缓发生率及尿素氮、碱性磷酸酶指标。结果:深度水解蛋白喂养组极低出生体重儿/低出生体重儿恢复出生体重天数、完全肠道喂养天数、胃管留置时间、住院天数较早产儿奶喂养组明显缩短(P0.05),每天体重增长优于早产儿组,喂养不耐受、宫外发育迟缓发生率明显低于早产儿组(P0.05),尿素氮、碱性磷酸酶无统计学差异(P0.05)。结论:深度水解蛋白奶用于不同体重早产儿早期喂养效果明显优于早产儿配方奶,其更有助于早产儿的生长发育。     

Attitudes to viability of preterm infants and their effect on figures for perinatal mortality.

OBJECTIVE--To examine how local attitudes to management of extreme preterm labour can influence data on perinatal mortality. DESIGN--One year prospective study in a geographically defined population. SETTING--The 17 perinatal units of Trent region. PATIENTS--All preterm infants of less than or equal to 32 weeks'' gestation in the Trent region. INTERVENTIONS--Infants who had been considered viable at birth were referred for intensive care; those who had been considered non-viable received terminal care. MAIN OUTCOME MEASURES--Whether each infant was born alive, dead, or alive but considered non-viable. RESULTS--Large differences were observed among units in the rates of delivery of infants of less than or equal to 27 weeks'' gestation (rates varied from 7.2 to 0 per 1000 births). These differences were not present in the data relating to infants of between 28 and 32 weeks'' gestation. The variation seemed to result from different approaches to the management of extreme preterm labour--that is, whether management took place in a labour ward or a gynaecology ward. CONCLUSIONS--Place of delivery of premature babies (less than or equal to 27 weeks'' gestation) may influence classification and hence figures for perinatal mortality. In addition, the fact that the onus of judgment regarding viability and classification is often placed on relatively junior staff might also affect the figures for perinatal mortality. The introduction of a standard recording system for all infants greater than 500 g would be advantageous.     

Oxidative stress in very low birth weight infants as measured by urinary 8-OHdG

Very low birth weight (VLBW) infants can be subjected to oxidative stress in the course of intensive care. We measured 8-hydroxydeoxyguanosine (8-OHdG), a biomarker of oxidative stress, and estimated the degree of oxidative stress in such infants. We also examined if the administered oxygen was related to oxidative stress. Urine samples of 50 Japanese VLBW infants [birth weights: 956.3+/-277.6g, and gestational ages: 28.0+/-2.6 weeks (mean +/- SD)] were collected on various postnatal days and 8-OHdG levels were determined using an ELISA kit. Sixteen term infants served as normal controls. As body weights at sampling increased, the average levels of urinary 8-OHdG decreased. 8-Hydroxydeoxyguanosine levels were: infants under 1000g, 29.5+/-16.4 micromol/mol creatinine (n = 24); 1000-1500g, 23.8+/-14.9 (n = 12); over 1500g, 16.1+/-8.5 (n = 14); and control, 10.9+/-7.2 (n = 16). Significant differences were found between <1000g group and > or = 1500g group (p = 0.0030), <1000g group and control (p < 0.0001), and 1000-1500g group and control (p = 0.0108). Also as postconceptional age at sampling increased, the average levels of 8-OHdG decreased. 8-Hydroxydeoxyguanosine levels were: infants before 252 days (36 weeks) of postconception: 27.4+/-15.5 micromol/mol creatinine (n = 34); after 252 days, 18.2+/-12.5 (n = 16). Differences between <252 days group and control (p < 0.0001), and <252 days group and > or = 252 days groups (p = 0.0253) were statistically significant. Among the three groups based on ambient oxygen concentration (21%, 22-29%, and > or = 30%) there was no significant difference (p = 0.417). The more premature the infants were, the more intense was the oxidative stress, hence, it is the prematurity rather than the administered oxygen which causes oxidative stress in VLBW infants. Drury et al. ["Urinary 8-hydroxydeoxyguanosine in infants and children" Free Radic. Res. 28 (1998) 423-4281 measured urinary 8-OHdG of 28 infants (24-40 weeks gestation) and found no gestation or birthweight related differences. This discrepancy seemed to be because of difference in birth weights and sampling period of the subjects.     

Anaerobic bacteria of periodontal pockets in course of periodontitis and premature labor

The aim of the study is was to evaluate anaerobic periodontal mikrobes in 120 postpartum mothers. Group I consisted of mothers with a birth weight of less than 2,500g and gestational age < 37 weeks. Group II included mothers with normal birth weight infants. All women in both of groups were subjected to a full-mouth periodontal examination to determine a periodontal status. The microbial investigation for anaerobic bacteria of deepest periodontal pockets was performed in 35 cases of periodontits. A significantly higher incidence of preterm low birth weight cases in patiens with periodontitis was documented. In addition higher variety of anaerobic bacteria of periodontal pockets in mothers with preterm low birth weight infants comparison to control group was observed.     

Neonatal intensive care and cost effectiveness.

During the past decade the rate of death among newborns weighing less than 1500 g at birth has decreased by approximately half. This dramatic reduction has resulted from the application of research findings and technologic advances, but it has proved expensive. Perhaps as a consequence of articles demonstrating the costs as well as the recognition that the overall prevalence of disabilities in infants is relatively unchanged, neonatal intensive care has recently been viewed as a possible area for cost containment. We reviewed the literature on the cost of neonatal intensive care and the limited information on other expensive medical programs and found that the cost of neonatal intensive care compared favourably, especially for infants whose birth weight was 1000 to 1500 g. Better information on the outcome of infants of very low birth weight and comparable rigorous studies of the cost effectiveness of other expensive medical programs are required, and other less easily quantified factors must be considered before decisions are made to limit neonatal intensive care on the basis of gestational age or birth weight.     

Risk of premature birth in multifetal pregnancy.

The risk of preterm delivery (< 37 weeks of gestation) is approximately nine times higher in women with multifetal pregnancies than in women with singleton pregnancies. However, it is possible that the risk will vary according to gestational week. To assess the risk of premature birth within 1 week by gestational age among multifetal pregnancies and compare the estimated risk with that of singleton pregnancies, we analyzed 6,036,475 infants born in singleton pregnancies and 90,887 infants born in multifetal pregnancies in Japan (> or =22 weeks) over the 5-year period 1989-1993. An estimate of the risk of birth within 1 week at gestational week n was obtained by dividing the number of infants delivered at gestational week n by the number of infants delivered at or beyond gestational week n. The risk at 22 weeks was 0.9 per 1000 fetuses for singleton pregnancies and 5.0 per 1000 for multifetal pregnancies. The risk remained relatively stable until 27 weeks of gestation, then sharply increased toward 36 weeks of gestation in both singleton and multifetal pregnancies. The odds ratio for birth within 1 week for fetuses of multifetal pregnancies compared with fetuses of singleton pregnancies was 5.9 (95% CI, 5.4-6.5) at 22 weeks of gestation, increasing gradually with increasing gestational age until 33 weeks of gestation (13.7; 95% CI, 13.1-14.2) but declining thereafter to 8.8 (95% CI, 8.6-8.9) at 36 weeks of gestation. Results of data analysis for each year of the 5-year period did not differ substantially.     

Spontaneous preterm labour and delivery at under 34 weeks' gestation.

The management and outcome of 242 infants delivered between 26 and 34 weeks'' gestation in an obstetrical and neonatal regional referral centre as a result of spontaneous preterm labour were recorded prospectively. Results of the survey show that the decision to intervene and delay delivery will depend on the availability of neonatal intensive care facilities. Infants likely to require intensive neonatal care should be transferred in utero to a centre with these facilities. The use of steroids reduces the mortality of preterm infants. The maximum effect occurs between 30 and 32 weeks'' gestation, and there is no benefit after 34 weeks. If the weight is over 1500 g the mode of delivery of the preterm infant presenting by the breech does not influence outcome; if under 1500 g a caesarean section improves survival over those infants born by vaginal breech delivery.     

Factors associated with initiation and exclusive breastfeeding at hospital discharge: late preterm compared to 37 week gestation mother and infant cohort

Background

To investigate and examine the factors associated with initiation of, and exclusive breastfeeding at hospital discharge of, late preterm (34 ^0/7 - 36 ^6/7 weeks) compared to 37 week gestation (37 ^0/7 - 37 ^6/7 week) mother and baby pairs.

Methods

A retrospective population-based cohort study using a Perinatal National Minimum Data Set and clinical medical records review, at the Royal Hobart Hospital, Tasmania, Australia in 2006.

Results

Late preterm and 37 week gestation infants had low rates of initiation of breastfeeding within one hour of birth, 31 (21.1%) and 61 (41.5%) respectively. After multiple regression analysis, late preterm infants were less likely to initiate breastfeeding within one hour of birth (OR 0.3 95% CI 0.1, 0.7 p = 0.009) and were less likely to be discharged exclusively breastfeeding from hospital (OR 0.4 95% CI 0.1, 1.0 p = 0.04) compared to 37 week gestation infants.

Conclusion

A late preterm birth is predictive of breastfeeding failure, with late preterm infants at greater risk of not initiating breastfeeding and/or exclusively breastfeeding at hospital discharge, compared with those infants born at 37 weeks gestation. Stratifying breastfeeding outcomes by gestational age groups may help to identify those sub-populations at greatest risk of premature cessation of breastfeeding.

     

Incidence and duration of lactation and lactational performance among mothers of low-birth-weight and term infants.

The lactation experience of 55 mothers of 62 infants of low birth weight (2500 g or less) was prospectively compared with that of 55 mothers of 55 control infants (38 weeks'' gestation or more, birth weight more than 2500 g) born at the same institution. The incidence rates of lactation at delivery were 73% for the control group and 58% for the low-birth-weight group; 11% of the infants of low birth weight fed breast milk were never put to the breast. The mean age at first suckling was 277.3 hours in the low-birth-weight group, compared with 3.3 hours in the control group (p less than 0.0005). At first suckling 81% of the low-birth-weight infants and 25% of the control infants sucked poorly or refused the breast (p less than 0.001). At discharge 65% of the breast-milk-fed control infants were exclusively breast-fed, compared with 3% of the low-birth-weight infants fed breast milk (p less than 0.001). The incidence rates of lactation over time were similar in the control and low-birth-weight groups (51% v. 44% at 1 month, 29% v. 13% at 3 months, 13% v. 4% at 6 months and 4% v. 2% at 12 months). The mean duration of lactation was 3.2 months for the control group and 2.5 months for the low-birth-weight group. In the long term 37% of the low-birth-weight infants fed breast milk failed to breast-feed, compared with 2% of the control infants, and only 31% were exclusively breast-fed, compared with 85% of the control infants (p less than 0.001). However, the degree of satisfaction with the lactation experience was similar in the two groups. We conclude that mothers of low-birth-weight infants have good potential for lactation.     

Association between length of gestation and cervical DNA methylation of PTGER2 and LINE 1-HS

Worldwide, more than 1 in 10 infants is born prior to 37 weeks gestation. Preterm birth can lead to increased mortality risk and poor life-long health and neurodevelopmental outcomes. Whether environmental risk factors affect preterm birth through epigenetic phenomena is largely unstudied. We sought to determine whether preterm risk factors, such as smoke exposure and education, were associated with cervical DNA methylation in the prostaglandin E receptor 2 gene (PTGER2) and a repetitive element, long interspersed nuclear element-1 Homo sapiens-specific (LINE 1-HS). Second, we aimed to determine whether mid-pregnancy DNA methylation of these regions in cervical samples could predict the length of gestation. We obtained a cervical swab between 16–19 weeks gestation from 80 women participating in a Mexico City birth cohort, used pyrosequencing to analyze DNA methylation of PTGER2 and LINE 1-HS, and examined associations with maternal covariates. We used accelerated failure time models to analyze associations of DNA methylation with the length of gestation. DNA methylation of both sequences was associated with Pap smear inflammation. LINE 1-HS methylation was associated with smoke exposure, BMI and parity. In adjusted models, gestations were 3.3 days longer (95%CI 0.6, 6.0) for each interquartile range of PTGER2 DNA methylation. Higher LINE 1-HS methylation was associated with shorter gestations (-3.3 days, 95%CI -6.5, -0.2). In conclusion, cervical DNA methylation was associated with risk factors for preterm birth and the length of gestation.     

Maturation of the pituitary-thyroid axis during the perinatal period.

To clarify the maturation process of the pituitary-thyroid axis during the perinatal period, thyrotropin (TSH) response to thyrotropin releasing hormone (TRH) and serum thyroid hormone levels were examined in 26 healthy infants of 30 to 40 weeks gestation. A TRH stimulation test was performed on 10 to 20 postnatal days. Basal concentrations of serum thyroxine (T4), free thyroxine (free T4) and triiodothyronine (T3) were positively correlated to gestational age and birth weight (p less than 0.001-0.01). Seven infants of 30 to 35 gestational weeks demonstrated an exaggerated TSH response to TRH (49.7 +/- 6.7 microU/ml versus 22.1 +/- 4.8 microU/ml, p less than 0.001), which was gradually reduced with gestational age and normalized after 37 weeks gestation. A similar decrease in TSH responsiveness to TRH was also observed longitudinally in all of 5 high responders repeatedly examined. There was a negative correlation between basal or peak TSH concentrations and postconceptional age in high responders (r = -0.59 p less than 0.05, r = -0.66 p less than 0.01), whereas in the normal responders TSH response, remained at a constant level during 31 to 43 postconceptional weeks. On the other hand, there was no correlation between basal or peak TSH levels and serum thyroid hormones. These results indicate that (1) maturation of the pituitary-thyroid axis is intrinsically controlled by gestational age rather than by serum thyroid hormone levels, (2) hypersecretion of TSH in preterm infants induces a progressive increase in serum thyroid hormones, and (3) although there is individual variation in the maturation process, the feedback regulation of the pituitary-thyroid axis matures by approximately the 37th gestational week.     

Association between length of gestation and cervical DNA methylation of PTGER2 and LINE 1-HS

Worldwide, more than 1 in 10 infants is born prior to 37 weeks gestation. Preterm birth can lead to increased mortality risk and poor life-long health and neurodevelopmental outcomes. Whether environmental risk factors affect preterm birth through epigenetic phenomena is largely unstudied. We sought to determine whether preterm risk factors, such as smoke exposure and education, were associated with cervical DNA methylation in the prostaglandin E receptor 2 gene (PTGER2) and a repetitive element, long interspersed nuclear element-1 Homo sapiens-specific (LINE 1-HS). Second, we aimed to determine whether mid-pregnancy DNA methylation of these regions in cervical samples could predict the length of gestation. We obtained a cervical swab between 16–19 weeks gestation from 80 women participating in a Mexico City birth cohort, used pyrosequencing to analyze DNA methylation of PTGER2 and LINE 1-HS, and examined associations with maternal covariates. We used accelerated failure time models to analyze associations of DNA methylation with the length of gestation. DNA methylation of both sequences was associated with Pap smear inflammation. LINE 1-HS methylation was associated with smoke exposure, BMI and parity. In adjusted models, gestations were 3.3 days longer (95%CI 0.6, 6.0) for each interquartile range of PTGER2 DNA methylation. Higher LINE 1-HS methylation was associated with shorter gestations (-3.3 days, 95%CI -6.5, -0.2). In conclusion, cervical DNA methylation was associated with risk factors for preterm birth and the length of gestation.     

Epidemiology of bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD) is among the most common and serious sequelae of preterm birth. BPD affects at least one‐quarter of infants born with birth weights less than 1500 g. The incidence of BPD increases with decreasing gestational age and birth weight. Additional important risk factors include intrauterine growth restriction, sepsis, and prolonged exposure to mechanical ventilation and supplemental oxygen. The diagnosis of BPD predicts multiple adverse outcomes including chronic respiratory impairment and neurodevelopmental delay. This review summarizes the diagnostic criteria, incidence, risk factors, and long‐term outcomes of BPD. Birth Defects Research (Part A) 100:145–157, 2014. © 2014 Wiley Periodicals, Inc.     

Social adversity,low birth weight,and preterm delivery.

A prospective study of 483 pregnant women was undertaken to examine possible associations of social and psychiatric factors with both low birth weight (less than 2500 g) and preterm delivery (less than 37 weeks'' gestation). As few babies were born before term (n = 14) or with a low birth weight (n = 14) further analyses were conducted to investigate predictors of absolute birth weight and gestational age. Low income was found to be an independent predictor of birth weight when birth weight was treated both as a dichotomous and as a continuous variable. Unemployment was found to be associated with absolute birth weight. Although this effect was statistically accounted for by low income, a low income was frequently caused by unemployment. Smoking independently predicted absolute birth weight and tended to be associated with preterm delivery. None of the factors investigated was associated with gestational age. In contrast with previous findings, factors such as social class, adverse life events, and psychiatric state were not associated with birth outcome. The mechanism underlying the association between low income and low birth weight requires further investigation.     

Postnatal Temporal,Spatial and Modality Tuning of Nociceptive Cutaneous Flexion Reflexes in Human Infants

Cutaneous flexion reflexes are amongst the first behavioural responses to develop and are essential for the protection and survival of the newborn organism. Despite this, there has been no detailed, quantitative study of their maturation in human neonates. Here we use surface electromyographic (EMG) recording of biceps femoris activity in preterm (<37 weeks gestation, GA) and term (≥37 weeks GA) human infants, less than 14 days old, in response to tactile, punctate and clinically required skin-breaking lance stimulation of the heel. We show that all infants display a robust and long duration flexion reflex (>4 seconds) to a single noxious skin lance which decreases significantly with gestational age. This reflex is not restricted to the stimulated limb: heel lance evokes equal ipsilateral and contralateral reflexes in preterm and term infants. We further show that infant flexion withdrawal reflexes are not always nociceptive specific: in 29% of preterm infants, tactile stimulation evokes EMG activity that is indistinguishable from noxious stimulation. In 40% of term infants, tactile responses are also present but significantly smaller than nociceptive reflexes. Infant flexion reflexes are also evoked by application of calibrated punctate von Frey hairs (vFh), 0.8–17.2 g, to the heel. Von Frey hair thresholds increase significantly with gestational age and the magnitude of vFh evoked reflexes are significantly greater in preterm than term infants. Furthermore flexion reflexes in both groups are sensitized by repeated vFh stimulation. Thus human infant flexion reflexes differ in temporal, modality and spatial characteristics from those in adults. Reflex magnitude and tactile sensitivity decreases and nociceptive specificity and spatial organisation increases with gestational age. Strong, relatively non-specific, reflex sensitivity in early life may be important for driving postnatal activity dependent maturation of targeted spinal cord sensory circuits.     

择期经阴道宫颈环扎术与期待疗法治疗宫颈机能不全的效果比较

目的:比较择期经阴道宫颈环扎术以及期待疗法治疗宫颈机能不全的效果。方法:选择2017年10月~2019年10月我院收治的201例宫颈机能不全患者,将其随机分为两组。对照组100例患者采取期待疗法,即卧床休息,口服地屈孕酮,每次服用的剂量为10 mg,每日2次,一直服药到30孕周;观察组101例患者择期经阴道宫颈环扎术,比较两组的早产率、成功妊娠率、新生儿出生体重以及分娩孕周。结果:对照组100例宫颈机能不全患者中,22例患者流产(占22.00%),78例患者获得活婴(占78.00%),78例成功分娩的患者中,47例患者≥37周分娩,31例患者<37周分娩,早产率为39.74%(31/78)。观察组的101例患者中,8例患者流产(占7.92%),93例患者获得活婴(占92.08%)。93例成功分娩的患者中,81例患者≥37周分娩,12例患者<37周分娩,早产率为12.90%(12/93);12例早产的患者中,4例患者由于胎膜早破和胎儿窘迫,而在孕32~33周采取剖宫产手术,2例患者由于胎膜早破臀位,而在孕35~36周时采取剖宫产手术,6例患者在孕35~36周早产。观察组宫颈机能不全患者的早产率明显低于对照组(P<0.05),且成功妊娠率、新生儿出生体重以及分娩孕周明显高于或长于对照组(P<0.05)。结论:与期待疗法相比较,择期经阴道宫颈环扎术不但可以明显延长宫颈机能不全患者的分娩孕周,提高成功妊娠率,还能改善新生儿的预后、降低早产的风险。     

Patterns of low birth weight in the Bengali newborns

This paper examines the distribution of low birth weight (2500 g or less) by gestation time, sex, maternal age, parity (birth order), socioeconomic conditions, and season of birth among 5117 single live births born to Bengali mothers at the Ramakrishna Mission Seva Pratisthan Hospital in Calcutta, India. Preterm infants have low birth weight significantly more often than their full term counterparts. Female infants have low birth weights significantly more often than male infants. The infants of poor mothers have lower birth weights in higher order births more often than infants of higher orders born to well-off mothers. Teenaged mothers produce low birth weight babies significantly more often than older mothers. Although the relationship is not significant, low birth weight infants occur more often among 1st and late born infants and less often among 2nd born infants. The season of birth is not significantly associated with birth weight. Less than 10% of low birth weight infants are pre-term, while the rest are full term. The great majority of low birth weight infants are small-for-gestational-age; the minority are small due to curtailed gestational age. The proportion of infants weighing less than 2001 g is only 9%; this figure tallies closely with earlier studies of India.     

Perinatal outcome of singletons and twins after assisted conception: a systematic review of controlled studies

Objective To compare the perinatal outcome of singleton and twin pregnancies between natural and assisted conceptions.Design Systematic review of controlled studies published 1985-2002.Studies reviewed 25 studies were included of which 17 had matched and 8 had non-matched controls.Main outcome measures Very preterm birth, preterm birth, very low birth weight, low birth weight, small for gestational age, caesarean section, admission to neonatal intensive care unit, and perinatal mortality.Results For singletons, studies with matched controls indicated a relative risk of 3.27 (95% confidence interval 2.03 to 5.28) for very preterm (< 32 weeks) and 2.04 (1.80 to 2.32) for preterm (< 37 weeks) birth in pregnancies after assisted conception. Relative risks were 3.00 (2.07 to 4.36) for very low birth weight (< 1500 g), 1.70 (1.50 to 1.92) for low birth weight (< 2500 g), 1.40 (1.15 to 1.71) for small for gestational age, 1.54 (1.44 to 1.66) for caesarean section, 1.27 (1.16 to 1.40) for admission to a neonatal intensive care unit, and 1.68 (1.11 to 2.55) for perinatal mortality. Results of the non-matched studies were similar. In matched studies of twin gestations, relative risks were 0.95 (0.78 to 1.15) for very preterm birth, 1.07 (1.02 to 1.13) for preterm birth, 0.89 (0.74 to 1.07) for very low birth weight, 1.03 (0.99 to 1.08) for low birth weight, 1.27 (0.97 to 1.65) for small for gestational age, 1.21 (1.11 to 1.32) for caesarean section, 1.05 (1.01 to 1.09) for admission to a neonatal intensive care unit, and 0.58 (0.44 to 0.77) for perinatal mortality. The non-matched studies mostly showed similar trends.Conclusions Singleton pregnancies from assisted reproduction have a significantly worse perinatal outcome than non-assisted singleton pregnancies, but this is less so for twin pregnancies. In twin pregnancies, perinatal mortality is about 40% lower after assisted compared with natural conception.