Birth Weight Ratio Research Articles

Influence of intrauterine and extrauterine growth on neurodevelopmental outcome of monozygotic twins

There have been indications that intrauterine and early extrauterine growth can influence childhood mental and motor function. The objective of the present study was to evaluate the influence of intrauterine growth restriction and early extrauterine head growth on the neurodevelopmental outcome of monozygotic twins. Thirty-six monozygous twin pairs were evaluated at the corrected age of 12 to 42 months. Intrauterine growth restriction was quantified using the fetal growth ratio. The effects of birth weight ratio, head circumference at birth and current head circumference on mental and motor outcomes were estimated using mixed-effect linear regression models. Separate estimates of the between (interpair) and within (intrapair) effects of each measure on development were thus obtained. Neurodevelopment was assessed with the Bayley Scales of Infant Development, 2nd edition, by a psychologist blind to the exposure. A standardized neurological examination was performed by a neuropediatrician who was unaware of the exposures under investigation. After adjustment, birth weight ratio and head circumference at birth were not associated with motor or mental outcomes. Current head circumference was associated with mental but not with motor outcomes. Only the intrapair twin effect was significant. An increase of 1 cm in current head circumference of one twin compared with the other was associated with 3.2 points higher in Mental Developmental Index (95%CI = 1.06-5.32; P < 0.03). Thus, no effect of intrauterine growth was found on cognition and only postnatal head growth was associated with cognition. This effect was not shared by the co-twin.

Genetic (co)variances and breeding value estimation of Gompertz growth curve parameters in Finnish Yorkshire boars, gilts and barrows

This paper's objectives were to estimate the genetic (co)variance components of the Gompertz growth curve parameters and to evaluate the relationship of estimated breeding values (EBV) based on average daily gain (ADG) and Gompertz growth curves. Finnish Yorkshire central test station performance data was obtained from the Faba Breeding (Vantaa, Finland). The final data set included 121,488 weight records from 10,111 pigs. Heritability estimates for the Gompertz growth parameters mature weight (alpha), logarithm of mature weight to birth weight ratio (beta) and maturation rate (kappa) were 0.44, 0.55 and 0.31, respectively. Genotypic and phenotypic correlations between the growth curve parameters were high and mainly negative. The only positive relationship was found between alpha and beta. Pearson and Spearman rank correlation coefficients between EBV for ADG and daily gain calculated from Gompertz growth curves were 0.79. The Spearman rank correlation between the sire EBV for ADG and Gompertz growth curve parameter-based ADG for all sires with at least 15 progeny was 0.86. Growth curves differ significantly between individuals and this information could be utilized for selection purposes when improving growth rate in pigs.

PAHs from the Inside Out: Birth Outcomes Vary among Ethnic Groups in NYC

In humans, the developmental hazards associated with exposure to urban ambient air pollution, particularly polycyclic aromatic hydrocarbons (PAHs), continue to be debated. PAHs are formed during the incomplete burning of fossil fuels, wood, and tobacco products, with high levels found in automobile exhaust and industrial emissions. This month, researchers at Columbia University report that prenatal exposure to PAHs affects birth outcomes differently in pregnant African-American and Dominican women [EHP 116:658–665; Choi et al.]. Previously the same group showed that approximately 40% of the children studied had in utero DNA damage as a result of exposure to air pollution from fossil fuel combustion. The same group has also examined the link between prenatal exposure to airborne PAHs and intrauterine growth restriction, a condition in which the fetus is smaller than expected for the length of pregnancy, and has shown a relationship between prenatal exposure to PAHs and reduced birth weight in African Americans in New York City and whites in Krakow, Poland. In the current prospective study, the team recruited women from local prenatal care clinics in New York City. The women lived in three neighborhoods served by Columbia’s Mailman School of Public Health. The target population was limited to women aged 18–35 who did not use tobacco products or illicit drugs; did not have diabetes, hypertension, or known HIV; and had started prenatal care by the twentieth week of pregnancy. The researchers interviewed each woman in the last trimester of pregnancy, in her home, to obtain information on health, lifestyle, and exposure history. They also gave each woman a small backpack containing an air monitor for measuring PAH exposure. The personal air monitor operated continuously over a 48-hour period at 4 L per minute to simulate normal lung capacity, collecting particulate and semivolatile vapor and aerosol PAHs. Filters were replaced every 48 hours and analyzed for pyrene and carcinogenic PAHs, including benzo[a]pyrene (BaP), which has been associated with adverse reproductive and developmental effects in laboratory animals and humans. The investigators collected birth outcome information from medical records, including gestational age, which was estimated by attending clinicians and validated by sonogram. The analysis included 616 mother–child pairs. The results showed universal and variable personal exposure to PAHs, with a mean exposure to BaP (0.368 ng/m3) consistent with the ambient BaP level in New York City. Among African Americans, prenatal PAH exposure increased the risk of preterm delivery and the likelihood of infants being born small for gestational age (SGA; meaning birth weight is below the tenth percentile of babies of the same gestational age). As prenatal PAH exposure increased, so did cephalization index, a ratio of head circumference to birth weight that can presage developmental problems later in childhood. Among Dominicans, there was no association between airborne PAH exposure and significant increase in risk of SGA, reduced birth weight ratio, increased cephalization index, or preterm delivery. This could reflect healthful cultural practices among recent Dominican immigrants such as more nutritious diets and more supportive social networks. The possible health-protective effects of the Dominicans’ cultural habits and the specific factors underlying the greater vulnerability of the African-American subjects warrant further study.

The male/female ratio of spontaneous fetal deaths and low birthweight in Japan

The male/female ratio of spontaneous fetal deaths and low birthweight in Japan

Magnetic resonance imaging in pregnancies complicated by gestational diabetes predicts infant birthweight ratio and neonatal morbidity.

The use of magnetic resonance imaging (MRI) has been shown to be safe during pregnancy and can accurately assess fetal fat and rate of growth. The purpose of this study was to investigate with MRI the relationship between maternal weight, fat distribution, and glucose levels and neonatal birthweight ratio, percent fat, and infant outcome in pregnancies complicated by gestational diabetes. Twenty gestational diabetic women were studied at 36 to 38 weeks' gestation with hemoglobin A1c, a glucose tolerance test and maternal body fat by electrical impedance. MRI scans of the maternal upper arm and from her zyphoid process to her pubic symphysis, including all fetal components, were analyzed for percent fat of the mother's arm and trunk and her fetus' trunk. All variables were then related to infant outcome (birthweight, birthweight ratio, and neonatal morbidity). Maternal body composition was related to maternal weight (p = 0.012, r = 0.54), as was maternal arm fat (p < 0.005, r = 0.60). Arm fat did correlate with trunk fat, but trunk fat did not correlate was well with weight (p = NS). Although maternal Hb A1c correlated with maternal weight (p = 0.05, r = 0.43), it did not correlate with infant birthweight. In contrast, maternal mean glucose levels correlated with both maternal and infant weight and infant birthweight ratio (p = 0.05, r = 0.60; p = 0.05, r = 0.42; and p = 0.01, r = 0.64, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

A practical approach to managing the risks of iodine deficiency in flocks using thyroid-weight:birthweight ratios of lambs

AIM: To establish a protocol for determining the iodine status of a flock and managing the risks of iodine deficiency, using thyroid-weight:birthweight ratios of newborn lambs and serum iodine concentrations of ewes. METHODS: Data were collected from iodine supplementation studies in Southland and Rangitikei, of sheep fed exclusively pasture or pasture plus brassica during the latter half of gestation (n=350, or 89 per treatment group). The ewes were supplemented pre-mating or at the time of pregnancy scanning with an injection of long-acting iodised oil. Serum iodine concentrations were measured in ewes prepartum in Rangitikei and postpartum at both locations. The thyroid-weight:birthweight ratios (as g/kg) in 229 newborn lambs were determined at post-mortem examination and compared between iodine supplemented vs unsupplemented flocks using probit analysis. Samples of pasture and kale were analysed monthly for determination of iodine and selenium. RESULTS: Initial mean serum iodine concentration of all ewes was 41 µg iodine/L. Supplementation increased serum iodine concentrations regardless of forage fed, and concentrations remained high for between 127 and 206 days. The range of thyroid-weight:birthweight ratios in lambs from supplemented ewes was 0.09–0.70 (mean 0.35, standard deviation (SD) 0.147) g/kg. Among lambs from unsupplemented ewes, the range was much wider (0.21–8.5; mean 1.61, SD 1.95 g/kg). About half of those ratios were >0.8 g/kg and clearly indicative of goitre, including 62% from the groups on brassica and 18% from the Rangitikei group fed exclusively pasture. Probit calculations showed that a ratio of 0.40 (95% confidence interval (CI)=0.29–0.47) g/kg predicted with 35% probability, and a ratio of 0.80 (95% CI=0.70–0.99) g/kg predicted with 90% probability that a lamb came from an unsupplemented flock. CONCLUSIONS: Compared to iodine concentrations in forages, thyroid-weight:birthweight ratios more accurately reflected the iodine status of the flock and could be used to identify which flocks to supplement the following year. Serum iodine concentrations of ewes measured before or after lambing did not reflect forage fed, but values near 40 µg/L were associated with goitrous lambs. CLINICAL RELEVANCE: Thyroid-weight:birthweight ratios >0.8 g/kg were indicative of iodine deficiency, and ewes should be supplemented pre-mating or during pregnancy to prevent goitre the following year. Ratios <0.4 g/kg rarely occurred among deficient flocks, so the probability of benefit from supplementation was low. Intermediate ratios were ambiguous, and the iodine status of the flock could not be determined from biomarkers. In such cases individual-farm supplementation trials might be required to detect and manage the risks of marginal deficiency.

Assessing fetal growth impairments based on family data as a tool for identifying high-risk babies. An example with neonatal mortality

BackgroundLow birth weight is associated with an increased risk of neonatal and infant mortality and morbidity, as well as with other adverse conditions later in life. Since the birth weight-specific mortality of a second child depends on the birth weight of an older sibling, a failure to achieve the biologically intended size appears to increase the risk of adverse outcome even in babies who are not classified as small for gestation. In this study, we aimed at quantifying the risk of neonatal death as a function of a baby's failure to fulfil its biologic growth potential across the whole distribution of birth weight.MethodsWe predicted the birth weight of 411,957 second babies born in Denmark (1979–2002), given the birth weight of the first, and examined how the ratio of achieved birth weight to predicted birth weight performed in predicting neonatal mortality.ResultsFor any achieved birth weight category, the risk of neonatal death increased with decreasing birth weight ratio. However, the risk of neonatal death increased with decreasing birth weight, even among babies who achieved their predicted birth weight.ConclusionWhile a low achieved birth weight was a stronger predictor of mortality, a failure to achieve the predicted birth weight was associated with increased mortality at virtually all birth weights. Use of family data may allow identification of children at risk of adverse health outcomes, especially among babies with apparently "normal" growth.

Placenta weight percentile curves for singleton deliveries

To produce population-based, gender- and gestational-age-specific centile curves for placental weight. Population study. Medical Birth Registry of Norway. All singleton live births in Norway from 1 January 1999 to 31 December 2002. In a cohort of children born in Norway, placental weights and the ratio of the birthweight to the placental weight were analysed to produce percentile curves. Placental weight, birthweight-to-placental weight ratio. Tables and figures are presented for placental percentiles curves according to gestational age and gender. Also, tables and figures are presented for the ratio of birthweight to placental weight. CONCLUSIONS To our knowledge, this is the first time that population percentile curves have been produced for placental weights and hence for the ratio of birthweight to placental weight. These percentile curves may act as a reference for other populations as well until population-specific curves can be produced.

Effects of Propoxur on the Reproductive System of Male Rats

The reproductive toxicity of propoxur (2-isopropoxy-phenyl-N-methylcarbamate), a carbamate pesticide, was investigated in adult male Wistar rats exposed to 0, 1.73, 2.6, and 5.2 mg/kg body weight/day for 90 successive days. Results obtained from this study showed a significant (p < 0.05) concentration-dependent increase in food consumption, relative weights of testis, epididymis and kidneys with maximum effects observed at the highest dose of propoxur (5.2 mg/kg) compared to the control. On the contrary, there was a significant (p < 0.05) decrease in the body weight gain, sperm density, serum and intratesticular total cholesterol concentrations, and intratesticular total proteins in rats treated with propoxur at the dose of 5.2 mg/kg body weight. Propoxur had no significant effect on gestation, fertility and parturition indices, average birth weight, litter size and pups sex ratio of untreated female rats mated with treated males rats. These results suggested that propoxur increased food consumption, relative weight of reproductive and detoxication organs, decreased body weight gain and sperm density per gram of cauda epididymis without affecting the reproductive performances.

Relationship between Thrombophilic Disorders and Type of Severe Early-Onset Hypertensive Disorder of Pregnancy

Objective: To determine whether specific subtypes of early-onset hypertensive disorders of pregnancy (haemolysis, elevated liver enzymes, low platelets [HELLP] syndrome; severe preeclampsia; eclampsia; and fetal growth restriction) differ in increased prevalences of thrombophilic disorders. Design: Cohort study. Setting: Two university hospitals in Amsterdam, the Netherlands. Population: 216 patients participating in a randomized clinical trial with severe and early-onset hypertensive disorders of pregnancy. Methods: More than 3 months after delivery, all patients were invited for a thrombophilia screening protocol, including hereditary thrombophilic disorders (Factor II or V-Leiden mutation, APC-resistance, protein S deficiency), antiphospholipid antibodies (anticardiolipin antibodies and lupus anticoagulant activity), and hyperhomocysteinemia (before and after methionin challenge). Disease expression was classified by HELLP syndrome, severe preeclampsia, or neonatal birth weight ratio below the median (0.65). Univariate and multinomial regression analyses examined the association of disease expression with thrombophilic disorders, and other associated factors (chronic hypertension, smoking, body mass index, positive family history of cardiovascular morbidity, and demographic parameters). Main outcome measures: incidence of thrombophilic disorders in different subtypes of disease. Results: Overall prevalence of thrombophilic disorders in 206 (95%) screened women was 36%. Chronic hypertension was present in 32%, and 34% had a positive family history of cardiovascular morbidity. Multinomial regression analysis showed that hereditary thrombophilia was more frequent among women with infants with a birth weight ratio <0.65 than in women with HELLP syndrome or severe preeclampsia (p = 0.01, OR 5.1 (1.5 to 7.3) and OR 3.4 (1.1 to 10.6), respectively). High body mass index was less frequent in women with HELLP syndrome than in those with severe preeclampsia or fetal growth restriction (p = 0.06, OR 0.5 (0.3 to 0.9) and OR 0.4 (0.2 to 1.0), respectively). Conclusion: In this population, the high prevalence of thrombophilic factors and chronic hypertension was confirmed. There were small differences between groups. Hereditary thrombophilic disorders were associated with fetal growth restriction but not with type of maternal disease, suggesting an effect on placental function. Maternal body mass index was lower in women with HELLP syndrome.

Medical Tourism and the Libyan National Health Services

Medical Tourism and the Libyan National Health Services

Age at Menarche: Influences of Prenatal and Postnatal Growth

The objective of this study was to determine the influence of birth weight and postnatal weight gain on age at menarche. This was a prospective cohort study where girls from the West Australian Pregnancy (Raine) Cohort Study were followed prospectively from fetal life (18 wk of pregnancy) to adolescence (12-14 yr). Age at menarche was the main outcome measure. Growth status at birth was judged by expected birth weight ratio (EBW; a ratio of observed infant's birth weight over median birth weight appropriate for maternal age, weight, height, parity, infant sex, and gestational age). Postnatal growth status was judged by body mass index (BMI). Both EBW (P = 0.020) and BMI in childhood (8 yr of age) (P < 0.001) were associated with age at menarche. Menarche occurred earlier in girls with lower EBW and higher BMI. We have demonstrated for the first time that both birth weight and weight gain in childhood are associated with age at menarche. Weight gain before birth and subsequent weight gain up to the age of 8 yr were found to have opposing influences on the timing of menarche. Lower EBW combined with higher BMI during childhood predicted early age at menarche, and this relationship existed across normal birth weight and BMI ranges.

Placental Traits in Pen-fed Goats and Goats Kept on Rangeland

Mallado, M., Olivares, L., Diaz, H. and Villarreal, J.A. 2006. Placental traits in pen-fed goats and goats kept on rangeland. J. Appl. Anim. Res., 29: 133–136. To determine if rearing conditions (pen vs. extensive grazing) alters placental development, mixed-breed goats were kept either under intensive (n=31) or extensive (n=40) condition in a desert rangeland. Does kept under pen conditions had higher (P<0.01) serum glucose, urea, cholesterol, total proteins and phosphorus values than grazing goats. There was no effect of rearing conditions on kid birth weight, but placentas from nutrient-restricted mothers were 56% heavier (P<0.01) at parturition than pen-fed does. Placentas from the grazing goats had less placentomes and feto-maternal contact area compared to pen-fed goats. Body condition score was significantly correlated with placental weight (r= −0.69) and placenta to birth weight ratio (r= 0.74). These results showed that live weight of offspring born from nutrient-restricted mothers was not compromised, but chronic nutrient deprivation resulted in larger placentas with fewer placentomes.

The Effect of Air Pollution on Low Birth Weight: A Cohort Study

Aim: The paper aims to determine the effects of maternal exposures to essential air pollutants on low birth weight (LBW) in Tehran, Iran. Methods: One thousands neonates were randomly selected of all live singletons born during 2000-2002, to 18-35 years old house wives mothers, living in one of the selected regions of the study (inside the boundary of 5 kilometers radius from four air quality control stations of Tehran. Linear regression and logistic regression were used to estimate the effects of air pollution on low birth weight. Results: Low birth weight ratio was increased by the accretion of carbon monoxide, sulfur dioxide, nitrogen dioxide, and Ozone in the third trimester of the pregnancies. There was no statistical significant trend in LBW ratios in case of particulate matters ≤10μgr/m (PM10). The logistic model confirmed that the highest risk for low birth weight was related to CO. Multiple regression revealed CO as the most effective air pollutant in lowering the birth weight. Conclusions: Low birth weight rates increases in the presence of essential air pollutants. This signifies the risk of neonatal diseases, hospitalizations and infants' higher mortality rates. Additionally, it might increase the cost of care and treatment.

Reference values for the weight of freshly delivered term placentas and for placental weight–birth weight ratios

Background There is evidence for a correlation between placental weight and future chronic disease, notably hypertension and diabetes. However, there are no reference scales for placentas that are readily weighed in the delivery room. Methods This cross-sectional study generated reference values for the weight of freshly delivered untrimmed placentas, and placental weight–birth weight (pw/bw) ratios from a database of 11,141 uncomplicated singleton term pregnancies (37–42 weeks). The data analysis followed stringent validated and state of the art methodological recommendations. A regression model was fitted to estimate the mean and standard deviation for placental weight and pw/bw ratios at each week of gestational age. Results Reference scales, percentile tables and regression equations are presented for placental weights according to the mode of delivery and for pw/bw ratios. Mean placental weight from vaginal deliveries was 76 g lighter than from Caesarean sections (545 ± 107 g versus 621 ± 139 g, respectively, P < 0.05). Mean placental weight increased by 60 g from 37 to 42 weeks irrespective of the mode of delivery. The pw/bw ratio decreased from 17.6 to 15.6 between 37 and 42 weeks. Conclusion For the first time, reference values for freshly delivered term placental weights depending on the mode of delivery were generated. In the light of growing evidence for a correlation of placental weight with chronic diseases in later life, these values provide the possibility to judge placentas at site for abnormalities in weight and to estimate the potential risks for chronic diseases in later life.

Two Definitions of “Small Size at Birth” as Predictors of Motor Development at Six Months

Small babies are known to be at increased risk for a wide range of difficulties. In predicting risk, it may be more informative to estimate smallness in relation to family norm (using the birth weight of an older sibling) rather than to use the standard "small-for-gestational-age" (SGA z-score) measure. For 10,577 babies born to women enrolled in the Danish National Birth Cohort, we calculated a "birth-weight ratio" (actual birth weight/expected birth weight predicted from older sibling x 100). We identified babies in the lowest decile of the birth-weight ratio (</=87.7% for boys and </=87.6% for girls) and compared them with babies in the lowest decile of the sex- and gestational age-specific distribution (SGA z-score). We evaluated how these definitions predicted motor development. We also compared how selected predictors of birth weight influenced the classification of the baby according to the birth-weight ratio and according to the SGA z-score. Birth-weight ratio and SGA identified 1058 and 1059 babies, respectively, with 738 identified by both methods. A low birth-weight ratio predicted delayed motor development slightly better than did SGA. Babies classified as too small solely by the SGA criterion were more often born to small or smoking mothers than those identified solely by the birth-weight ratio. The combined use of the birth-weight ratio and SGA may provide a more sensitive tool for identifying babies at risk. The birth-weight ratio is less likely to classify babies as small based on their mothers' body size, identifying instead babies who were substantially smaller than their sibling.

Periodontal Diseases and the Risk of Preterm Birth and Low Birth Weight: A Meta‐Analysis

This meta-analysis of periodontal disease in relation to the risk of preterm birth/low birth weight (PTB/ LBW) is based on two case-control studies and three prospective cohort studies that met pre-stated inclusion criteria. Information on the designs of the studies, characteristics of the study population, exposure and outcome measures, control for confounders, and risk estimates were abstracted independently by two investigators using a standard protocol. Pregnant women with periodontal disease had an overall adjusted risk of preterm birth that was 4.28 (95% confidence interval [CI], 2.62 to 6.99; P <0.005) times that risk for healthy subjects. The overall adjusted odds ratio of preterm low birth weight was 5.28 (95% CI, 2.21 to 12.62; P <0.005), while the overall adjusted odds ratio of a delivery of either PTB or LBW was 2.30 (95% CI, 1.21 to 4.38; P <0.005). Our findings indicate that periodontal diseases in the pregnant mother significantly increase the risk of subsequent preterm birth or low birth weight. While it remains important to promote good oral hygiene during routine prenatal visits, there is no convincing evidence, on the basis of existing case control and prospective studies, that treatment of periodontal disease will reduce the risk of preterm birth. Consequently, large randomized, placebo-controlled, masked clinical trials are required.

The effects of duration of in vitro maturation of bovine oocytes on subsequent development, quality and transfer of embryos

We examined the effects of IVM duration on rates of Korean Native Cow (KNC) first polar body extrusion, embryo development and offspring. Cumulus oocytes complexes were cultured in vitro for up to 24 h. Extrusion of the first polar body was highest at 16 h. At selected times during IVM, oocytes were fertilized and in vitro development was compared to blastocysts collected from superovulated KNC. After fertilization, the cleavage rate did not differ for oocytes with different durations of IVM, but the development rates of the 8-cell and blastocyst stages were significantly higher in IVM 18-h than other durations. The mean inner cell mass, trophectoderm and total cell numbers of in vivo blastocysts (40.0 ± 3.8, 87.5 ± 3.5 and 127.5 ± 1.6, respectively) were similar to those for IVM 18-h group. When in vitro- and in vivo-derived blastocysts were transferred to Holstein heifer recipients, pregnancy and abortion rates did not differ among treatments. Mean gestation length was significantly shorter for in vivo-derived blastocysts than those derived from oocytes with 24 h of IVM. Birth weight produced by the IVM 24-h group (32.0 ± 2.2 kg) was significantly higher than that of in vivo and IVM 18-h groups. The sex ratio of calves was similar between the in vivo and the IVM 24-h group, but all calves derived from the IVM 18-h group were males. Therefore, duration of bovine oocyte IVM played a critical role in embryo development and blastocyst cell number. In addition, it also affected birth weight and sex ratio.

Preweaning piglet mortality in relation to placental efficiency1

The relationship between placental efficiency (PLEFF, i.e., the ratio of birth weight [BWB] to placental weight [PLW]) and neonatal pig vitality as measured by the probability of preweaning death of live born piglets was examined for 1,036 live born piglets of 118 litters. The data were first analyzed to establish whether the relationships between PLEFF, PLW, and BWB were affected by parity (first vs. higher). Furthermore, the data collected were used to establish whether PLEFF is a better predictor of the risk of neonatal pig mortality before weaning than BWB and PLW. The relationships of BWB to PLW and PLEFF to PLW differed (P <0.01 and P <0.05, respectively) between piglets from gilts and sows. This difference appeared to be due mainly to an additional population of piglets with very large placentas in sows that were not present in gilts. Despite being significant, the courses of the relationships were essentially similar for piglets in gilts and in sows. For the curvilinear relationship of BWB to PLW, up to a certain threshold value, an increase of PLW resulted in an increase in BWB, and thereafter BWB did not change. A consequence of this is that PLEFF at relatively high PLW does not give the same information as PLEFF at relatively low PLW. For the second-order relationship of PLEFF to BWB, PLEFF increased with an increase in BWB, until BWB = 1,657 g, and decreased thereafter. The PLEFF decreased linearly with PLW. A change in PLW had a much larger impact on the value of PLEFF than a change in BWB. Although BWB and PLW were negatively associated with the chance of dying before weaning (P <0.001 and P <0.01, respectively), only PLEFF tended to be negatively associated with the chance of dying only before weaning (P = 0.08). Its underlying trait, BWB, played a greater role on the effect of PLEFF on the chance of preweaning death than PLW. In conclusion, PLEFF in swine is a complicated trait that should be treated with care. It is merely a mathematical derivative of BWB and PLW, whereby the extent to which BWB depends on PLW depends on the value of PLW. Placental functioning and fetal growth capacity, however, also have their effects on the value of BWB. It is concluded that, of the three traits (BWB, PLW, and PLEFF), the best predictor for the chance of preweaning mortality, which also happens to be easiest to measure, remains BWB.

240 GESTATION LENGTH AND BIRTH WEIGHT OF IN VITRO PRODUCED EMBRYOS FROM ZEBU DAIRY CATTLE

Gir cattle are a popular zebu dairy breed in tropical and subtropical regions because of their tolerance of heat stress and resistance to tick-borne disease. The use of in vitro embryo production (IVP) technology may help accelerate genetic improvement of this breed. However, in general, IVP systems have been implicated in the production of large offspring and a greater proportion of male calves. Natural breeding results in newborn Gir calves weighing around 25 kg despite the fact that dams may weigh over 500 kg. It is unknown whether in vitro-produced Gir embryos also result in large offspring. The aim of this work was to evaluate the effect of in vitro embryo production on gestation length, birth weight, and sex ratio in Gir cattle. COCs were harvested by oocyte pickup from mature non-lactating Gir cows and in vitro-matured in TCM 199 medium (Gibco, Sao Paulo, Brazil) with 10% inactivated estrous cow serum for 24 h under 5% CO2 at 38.5°C in air. Gir spermatozoa were obtained through the swim-up method and co-incubated with oocytes in Fert-TALP media (Parrish JJ et al. 1988 Biol. Reprod. 38, 1171–1180) with 10 μg/mL heparin (Sigma, Sao Paulo, Brazil) and 6 mg/mL fatty acid-free bovine albumin (Sigma) for 18 h in 5% CO2 at 38.5°C in air. Presumptive zygotes were co-cultured with their own cumulus cells in CR2aa medium (Wilkinson RF et al. 1996 Theriogenology 45, 41–49) with 10% fetal calf serum in humid atmosphere of 5% CO2 at 38.5°C in air. Fresh Day 7 blastocysts were transferred to synchronized B. indicus × B. taurus crossbred recipients. Data of gestation length, birth weight, and gender ratio from 26 IVP calves (IVP group) were recorded and compared to data obtained from Gir calves produced by artificial insemination or natural mating (n = 24; control group) using ANOVA or chi-square analysis. There was no difference (P &gt; 0.05) in gestation length between pregnancies of the IVP and control groups (mean ± SEM, 285.4 ± 1.5 vs. 284.4 ± 1.1 days, respectively). IVP and control calves showed similar (P &gt; 0.05) weight at calving (29.6 ± 0.9 vs. 26.9 ± 1.2 kg for IVP and control male calves, and 27.0 ± 2.5 vs. 25.2 ± 0.5 kg for IVP and control female calves, respectively). The percentage of male calves was greater (P &lt; 0.05) in the IVP group than in the control group (76.9% vs. 43.4%, respectively). IVP calves did not show abnormalities associated with Large Offspring Syndrome, such as breathing difficulty and perinatal death. These data suggest that in vitro production may affect the development of Gir embryos, biasing the sex ratio in a manner similar to previously reported for in vitro-produced embryos from Bos taurus breeds. This work was supported by FAPEMIG and CNPq.