Prognostic significance of prior preterm twin delivery on subsequent singleton pregnancy

OBJECTIVE: Our purpose was to determine whether preterm birth of twins is associated with an increased risk of preterm birth in a subsequent singleton pregnancy. STUDY DESIGN: The Medical University of South Carolina perinatal database was accessed to identify a cohort of patients who were delivered of twins followed by a singleton gestation (1981 to 1993). Maternal transports were excluded to minimize referral bias. Preterm birth was defined as < 37 weeks' gestation. Relative risks with 95% confidence intervals were calculated. RESULTS: One hundred forty-four patients were identified who were delivered of twins followed by a singleton gestation. Preterm delivery occurred in 86 (59.7%) of the twins and 21 (14.6%) of the subsequent singletons. Preterm birth of twins was associated with a significantly increased risk of preterm delivery in a subsequent singleton pregnancy (relative risk 2.87, 95% confidence interval 1.02 to 8.09). In the subset of women who were delivered of twins at < 30 weeks' gestation, 42% of the subsequent singletons were delivered preterm (relative risk 6.11, 95% confidence interval 2.07 to 18.02). The relative risk of preterm birth of a singleton after delivery of twins between 30 and 34 weeks' gestation was 3.63 (95% confidence interval 1.02 to 12.92). However, if the preceding twins delivered between 34 and 37 weeks' gestation, the relative risk of preterm birth of the subsequent singleton was not significantly increased (relative risk 1.42, 95% confidence interval 0.40 to 5.01). CONCLUSIONS: Preterm birth of twins before 34 weeks' gestation is associated with a significant risk for preterm delivery in a subsequent singleton pregnancy. The magnitude of risk increases with decreasing gestational age of the preceding twin delivery.     

Vesico-sigmoidal fistulas of diverticular origin

OBJECTIVE: To evaluate the course and outcome of expectantly managed twin pregnancies with single fetal death in the second half of gestation. DESIGN: Case-controlled study of 29 consecutive pregnancies from 1973 to 1993, with sonographic evidence of a twin at 20 weeks gestation with antenatal demise later in pregnancy, matched for maternal parity with 58 twin pregnancies without fetal death and delivered in the same year as the index case. Outcome measures included the incidence of complications of pregnancy, gestational age and mode of delivery, placentation, and perinatal outcome. SETTING: University Hospital Rotterdam. RESULTS: The frequency and severity of pregnancy-induced hypertensive disorders was significantly higher in the study group than in controls. We found no differences between the study group and controls with regard to median gestational age at delivery (33 weeks versus 34 weeks) and median birthweight of liveborn infants (1880 g versus 2160 g). No consumptive coagulopathy was apparent in our 29 patients. The main cause of neonatal death was prematurity; multicystic encephalomalacia was not observed. CONCLUSIONS: Our results support expectant management in twin pregnancies complicated by single fetal death.     

Five-year follow-up study of saliva, mutans streptococci, lactobacilli and yeast counts in lymphoma patients

OBJECTIVE: To record the effect of aggressive perinatal management on neonatal outcome in the very premature infant. METHODS: A retrospective chart review of 114 infants born between 23 and 27 weeks' gestation, managed by one perinatal transport service at one hospital between July 1989 and December 1993. Fetuses > 23 weeks' gestation were considered viable and were managed with tocolytics, antibiotics, and surfactant at the discretion of the treating physician. Morbidity and mortality rates in the first 6 months, including stillbirths were analyzed. A major neurologic condition was defined as ultrasonographic evidence of grade 3 or 4 intraventricular hemorrhage or periventricular leukomalacia. RESULTS: Both neonatal mortality rate and the incidence of stillbirths decreased with advancing gestational age. Of 24 infants born at 23 weeks' gestation, 33% were stillborn and 13% were alive at 6 months. This survival rate improved to 48% for infants delivered at 24 weeks' gestation, and to 68%, 75%, and 71% for those delivered at 25, 26, and 27 weeks' gestation, respectively. The percentage of infants who survived without a major neurologic condition increased with advancing gestational age at delivery from 13% at 23 weeks' gestation to 40% at 24 weeks, 48% at 25 weeks, 70% at 26 weeks, and 71% at 27 weeks. The incidence of retinitis of prematurity, respiratory complications, and days spent in the hospital decreased with greater gestational age. CONCLUSIONS: An active plan of management for all gestations of > 23.9 weeks seems appropriate.     

Effect of amniotic fluid volume on neonatal outcome in diamniotic twin pregnancies

PROBLEM: We assessed neonatal outcome of normal diamniotic twin pregnancies with known amniotic fluid (AF) volume. METHOD: The AF volume was empirically determined in 39 diamniotic twin gestations. The neonates were stratified by AF volume and evaluated for clinical outcome, gestational age, lecithin-sphingomyelin (L/S) ratio, and birth weight. RESULTS: Neonatal complications did not significantly differ among infants delivered from pregnancies with low (155 to 404 mL), moderate (405 to 807 mL), or high (808 to 5,430 mL) volumes of AF. Relatively constant volumes of AF were maintained throughout the 27 to 38 week range of gestational age, with no apparent correlation between AF volume and gestational age. Variations in the L/S ratio and newborn birth weights were also independent of AF volume. Gestational age was the only significant determinant of the frequency of neonatal complications. CONCLUSION: Amniotic fluid volume does not greatly affect neonatal outcome in normal diamniotic twin pregnancies.     

Perinatal outcome of pregnancies after assisted reproduction: a case-control study

PURPOSE: A matched case-control study of all pregnancies obtained after either IVF or ICSI was conducted to investigate the perinatal outcome. METHODS: Three hundred eleven singleton and 115 twin pregnancies obtained after assisted reproduction were studied. Controls were selected from a regional register and were matched for maternal age, parity, singleton or twin pregnancy, and date of delivery. RESULTS: No significant difference was observed for gestational age at delivery, birth weight, incidence of congenital anomalies, and incidence of perinatal mortality between ART (singleton and twin) pregnancies and spontaneous controls. ART twin pregnancies showed a higher incidence of preterm deliveries than control pregnancies (52 vs 42%; P < 0.05) and needed more neonatal intensive care (47 vs 26%; P < 0.05). CONCLUSIONS: From this case-control study it is concluded that the perinatal outcome of ART singleton pregnancies is not different from that in matched controls. ART twin pregnancies showed a higher incidence of preterm deliveries than control pregnancies and needed more neonatal intensive care.     

A comparison of sonographic growth curves of triplet and twin fetuses

Sonographic growth curves of 47 normal triplet pregnancies were compared with those of 71 uncomplicated twin gestations. Starting from the 25th week, the biparietal diameter in triplets was found to lag progressively compared with that of twins, reaching a mean difference of 2 weeks at 36 weeks gestation. Similarly, a significant difference was found between the femur length and head to abdomen circumference ratio growth curves of triplets and twins. It is concluded that as pregnancy continues from the 25th to the 36th gestational week, there is a significant delay in the growth patterns of normal triplet pregnancies compared with twin gestations.     

The anti-craving drug acamprosate inhibits the conditioned place aversion induced by naloxone-precipitated morphine withdrawal in rats

OBJECTIVE: To assess the influence of maternal race, age, marital status, and education on risk for earlier and later preterm births in twin pregnancies. METHODS: We analyzed 8109 white and 1906 black liveborn twin pregnancies in the Missouri Linked Sibship files for the years 1978-1990, using contingency tables and multiple logistic regression. RESULTS: Black twin gestations had 1.61-fold (95% confidence interval [CI] 1.46, 1.76) greater risk than whites for preterm birth before 34 weeks' gestation. However, there was no race difference after 33 weeks. Among whites, teen age, unmarried status, and education fewer than 12 years were independently associated with risk for delivery before 34 weeks in multivariate analysis (odds ratios [OR] 1.28-1.51, each P < or=.001). These associations were diminished or absent for preterm births after 33 weeks' gestation. White unmarried teen mothers with fewer than 12 years of education had 1.83-fold (95% CI 1.39, 2.40) greater risk for preterm birth before 34 weeks' gestation compared with white married women more than 19 years of age with at least 12 years of education. In blacks, this difference was 1.47-fold (95% CI 1.13, 1.92). In both races, these differences were absent after 33 weeks' gestation. CONCLUSION: Traditional sociodemographic risk factors were present for twin preterm birth, but mainly before 34 weeks' gestation. This, together with previous data from Missouri Linked Sibship files, indicates that dominant pathogenic mechanisms of early preterm birth in twin gestations are likely to be different from those causing later preterm twin birth. Therefore, gestational age should be accounted for in future studies seeking to identify predictive factors or biomechanisms for twin preterm birth.     

Cerebellar growth in normal and growth-restricted fetuses of multiple gestations

OBJECTIVE: Our purpose was to evaluate growth of the cerebellum in growth-restricted fetuses of twin and triplet gestations versus growth in normal in utero sibling(s) and in singleton gestations. STUDY DESIGN: An ultrasonographic study was conducted in a population of pregnant women with twin and triplet gestations. The control group was either the normal in utero sibling(s) when one fetus was growth restricted or normal twin and singleton pregnancies. Standard biometric measurements were obtained on all fetuses throughout pregnancy, including the transverse cerebellar diameter. However, only the last measurement was used for the analysis. Statistical analyses were conducted comparing growth of the transverse cerebellar diameter among the growth-restricted fetuses versus growth in the normal in utero fetal sibling(s) or other normal twin and singleton gestations. RESULTS: Pregnancies were categorized on the basis of the growth status of women with twin and triplet gestations: Group 1 (151) contained women with two fetuses appropriately grown for gestational age; group 2 (52) had one appropriately grown fetus and one with intrauterine growth restriction; group 3 (19) had two fetuses with intrauterine growth restriction. In addition, there were 30 triplet gestations (group 4), five of which had growth-restricted fetuses, and group 5 contained 1405 singleton pregnancies. In all five groups there was a statistically significant relationship between transverse cerebellar diameter and gestational age (p < 0.0001). There was also no significant difference between growth of the transverse cerebellar diameter in the appropriately grown and growth-restricted siblings and among normal singleton and twin pregnancy groups. In most cases of growth-restricted fetuses, except for the transverse cerebellar diameter measurements, all other biometric parameters were < 10th percentile. CONCLUSION: These data confirm the relative preservation of normal cerebellar growth in growth-restricted fetuses and a similar rate of growth in singleton and multifetal gestations. The transverse cerebellar diameter therefore represents an independent biometric parameter that can be used in both singleton and multifetal pregnancies to assess normal and deviant fetal growth.     

Evaluation of triplet growth status at birth using individualized growth assessment: comparison with conventional methods and development of a new classification system

A new growth classification system for triplets based on individual growth curve standards provides new information on the growth status of triplets at birth. OBJECTIVES. The objectives of this study were to characterize growth outcome at birth in triplet pregnancies using Individualized Growth Assessment methods, and to compare these results to conventional methods of growth outcome evaluation. STUDY DESIGN. Rossavik growth models derived from second-trimester ultrasound measurements were used to predict the birth characteristics of 21 triplet neonates. Actual measurements of weight, head, abdominal, and thigh circumferences at birth were compared to population standards and to predicted values, the latter by calculation of Growth Potential Realization Index (GPRI) values. GPRI values were calculated using singleton (measurement procedure correction) and triplet (measurement procedure correction+decreased soft tissue deposition) correction factors (SCF, TCF). Neonatal Growth Assessment Scores (NGAS) were calculated using both sets of GPRI values. RESULTS. Three types of triplet neonates were identified. Group I (33.3%) were normal with both types of NGAS values, had very few abnormal GPRI values or anatomic measurements, and were all appropriate for gestational age. Group III (14.3%) were abnormal with both types of NGAS values, most GPRI values were abnormal, and all were small for gestational age. Group II (52.4%) had abnormal NGAS values when calculated from GPRI values determined with SCF and normal NGAS values when calculated from GPRI values determined with TCF. All but one was AGA. Almost all GPRIWT and GPRIThC values were abnormal using SCF and normal using TCF. CONCLUSION. Although growth outcome in triplet neonates can be normal (Group I) or intrauterine growth retarded (Group III), the majority are in an intermediate group (Group II) characterized by a decrease in soft tissue mass, which may or may not be pathological.     

The limit of viability--neonatal outcome of infants born at 22 to 25 weeks' gestation

BACKGROUND: With improved survival of preterm infants, questions have been raised about the limit of viability. To provide better information and counseling for parents of infants about to be delivered after 22 to 25 weeks' gestation, we evaluated the mortality and neonatal morbidity of preterm infants born at these gestational ages. METHODS: We studied retrospectively all 142 infants born at 22 to 25 weeks' gestation (as judged by best obstetrical estimate) from May 1988 through September 1991 in a single hospital. Mortality in the first six months, including stillbirths, and neonatal morbidity (i.e., the presence of intracranial pathologic conditions, chronic lung disease, and retinopathy of prematurity) were analyzed. RESULTS: Fifty-six infants (39 percent) survived for six months. Survival improved with increasing gestational age; none of 29 infants born at 22 weeks' gestation survived, as compared with 6 of 40 (15 percent) born at 23 weeks, 19 of 34 (56 percent) born at 24 weeks, and 31 of 39 (79 percent) born at 25 weeks. There were seven stillbirths at 22 weeks' gestation and four stillbirths at 23 weeks. The more immature the infant, the higher the incidence of neonatal complications as determined by the number of days of mechanical ventilation, the length of the hospital stay, and the presence of retinopathy of prematurity, periventricular or intraventricular hemorrhage, or periventricular leukomalacia. Only 2 percent of infants born at 23 weeks' gestation survived without severe abnormalities on cranial ultrasonography, as compared with 21 percent of those born at 24 weeks and 69 percent of those born at 25 weeks. CONCLUSIONS: We believe that aggressive resuscitation of infants born at 25 weeks' gestation is indicated, but not of those born at 22 weeks. Whether the occasional child who is born at 23 or 24 weeks' gestation and does well justifies the considerable mortality and morbidity of the majority is a question that should be discussed by parents, health care providers, and society.     

How accurate is fetal biometry in the assessment of fetal age?

OBJECTIVE: The purpose of the study was to assess the accuracy of fetal biometry in the midtrimester of pregnancy in the assignment of fetal age. STUDY DESIGN: A total of 152 singleton, 67 twin, and 19 triplet gestations resulting from in vitro fertilization with ultrasonographic fetal biometry from 14 to 22 weeks made up the study population. A gestational age prediction equation was derived from singletons with the use of stepwise linear regression. This equation was compared with 38 previously published equations and then applied to the twin and triplet populations. RESULTS: Head circumference was the best predictor of gestational age (random error [SD] 3.77 days). Addition of abdominal circumference and femur length to head circumference improved the accuracy of the dating equation (random error 3.35 days). Most dating formulas had systematic errors of <1 week. The systematic error was -0.32 day for averaging the singleton-based predictions for twins and -1.26 days for triplets. CONCLUSIONS: Gestational age assessment with the use of fetal biometry from 14 to 22 weeks is accurate for singleton, twin, and triplet gestations.     

Acute and chronic fetal hypoxia in monochorionic and dichorionic twins

OBJECTIVE: To assess the risk for acute and chronic fetal hypoxia in twin pregnancies. METHODS: We investigated 50 sets of twins (24-38 weeks' gestation, 660-3200 g birth weight) admitted consecutively to our neonatal intensive care unit. Seventy-six infants were appropriate for gestational age (AGA; tenth to 90th percentile), 20 were small for gestational age (SGA; below the tenth percentile), and four were large for gestational age (above the 90th percentile). Twenty-six singleton AGA term newborns served as controls. Umbilical arterial pH was used as a marker for acute and umbilical venous erythropoietin concentration for chronic fetal hypoxia. The results are given as median followed by quartiles. RESULTS: We identified 40 sets of diamniotic-dichorionic twins and ten sets of diamniotic-monochorionic twins with transplacental vascular shunts. In the second-born twin, umbilical arterial pH was lower (7.29, 7.23-7.33) than in the firstborn (7.31, 7.25-7.34) (P = .03), and the incidence of a low pH (less than 7.20) was higher (19 versus 11%). Two second-born twins and none of the firstborn twins had an umbilical arterial pH less than 7.05. In SGA twins, the erythropoietin concentration was elevated (34.8, 22.8-325 mU/mL) compared with that in AGA twins (16.2, 8.2-26.6 mU/mL) (P < .01). In AGA twins, erythropoietin concentration did not differ from that in AGA singleton newborns (19.6, 14.7-31.6 mU/mL). In 12 of 17 twin sets with weight discordancy greater than 15% and in all five twin sets with weight difference greater than 25%, erythropoietin concentration was higher in the smaller twin. The proportion of infants and of complete sets with elevated erythropoietin levels was higher (P < .01) in monochorionic than in dichorionic pregnancies. CONCLUSION: The second-born twin is at increased risk for acute birth asphyxia. Fetal growth restriction in twin pregnancies is associated with chronic fetal hypoxia. Monochorionic twins are at higher risk for chronic fetal hypoxia than are dichorionic twins.     

Assessing the risk of gestational diabetes in twin gestation

This study examines the hypothesis that twin gestation is a risk factor for gestational diabetes. In a retrospective analysis, the incidence of gestational diabetes in twin and singleton pregnancies was determined in groups matched for maternal age, weight, and parity. One-hour oral glucose challenge tests (50 g) were used to screen 9185 pregnant women. Gestational diabetes was diagnosed when abnormal screens (> or = 130 mg/dL) were followed by two or more abnormal values on a 3-hour (100 g) glucose tolerance test using National Diabetes Data Group (NDDG) criteria. A twin gestation was identified in 1.5% (138/9185) of the pregnancies. Gestational diabetes was diagnosed in 5.8% (8/138) and 5.4% (439/9047) of the twin and singleton pregnancies, respectively. The incidence of gestational diabetes is similar for singleton and twin gestations.     

Atypical presentation of preeclampsia in high-order multifetal gestations

OBJECTIVE: To describe our experience with preeclampsia in high-order multifetal gestations. METHODS: Records for all triplet and quadruplet pregnancies delivered after 24 weeks' gestation from January 1988 through June 1994 were reviewed. All patients were treated with bed rest from 20 weeks' gestation onward and received corticosteroids weekly beginning at 24 weeks. Tocolytics were used as needed. RESULTS: Twenty-one triplet and eight quadruplet pregnancies were studied. The mean gestational age at delivery was 32.3 and 27.9 weeks, and mean birth weights were 1547 and 1028 g, respectively. Seventeen of 29 patients developed preeclampsia, 14 of the 21 triplet mothers and three of the eight quadruplet mothers. Among 16 patients who were delivered for preeclampsia, only eight had blood pressure (BP) elevation before delivery, whereas ten had epigastric pain, visual disturbances and/or headache; nine had elevated liver enzyme levels; and seven had low platelet counts. Only three patients had proteinuria, and only six had edema. Five women developed the syndrome of hemolysis, elevated liver enzymes, and low platelets postpartum, all of whom had normal BP before delivery. Two patients developed preeclampsia after delivery. A total of 95 infants were delivered, all by cesarean, of whom 93 (98%) survived. CONCLUSION: Preeclampsia is common in high-order multifetal gestations and often presents in an atypical manner. Hypertension is not always the presenting sign, and symptoms consistent with severe preeclampsia and abnormal laboratory values predominate.     

Prevalence of cerebral palsy in twins, triplets and quadruplets

BACKGROUND: Twins and triplets are at higher risk of cerebral palsy than singletons. This study investigated the degree of risk for cerebral palsy in twins, triplets and quadruplets, and identified factors associated with the increased risk. METHODS: The subjects were recruited from the Kinki University Twin and Higher Order Multiple Births Registry. RESULTS: The subjects were 705 twins pairs (1410 twins), 96 sets of triplets (287 triplets excluding one infant death), and 7 sets of quadruplets (27 quadruplets excluding one infant death), who were born after 1977. The prevalence of cerebral palsy was 0.9% among 1410 twins, 3.1% among 287 triplets, and 11.1% among 27 quadruplets. Furthermore, the risks of producing at least one child with cerebral palsy were 1.5%, 8.0%, 42.9% in twin, triplet, quadruplet pregnancies, respectively. After adjusting for each associated factor using logistic regression, the risk of cerebral palsy was significantly associated with decrease in gestational age and asphyxia. The odds ratio indicated that infants whose gestational age was < 32 weeks were 20 times more likely to develop cerebral palsy than infants whose gestational age was > or = 36 weeks. CONCLUSIONS: The prevalence of cerebral palsy in triplets and quadruplets was higher than that in twins. Lower gestational age was associated with a greater risk of cerebral palsy.     

Multifetal pregnancy reduction: evaluation of fetal growth in the remaining twins

OBJECTIVE: Our purpose was to study fetal growth after reduction of high-order multiple gestations to twins. STUDY DESIGN: Birth weight and gestational age data were collected for 236 triplet and greater multiple pregnancies reduced to twins (113 triplets, 89 quadruplets, and 34 quintuplets or above) and was compared with those of a control group of unreduced twins. RESULTS: Rates of intrauterine growth restriction per pregnancy were significantly different between the nonreduced and all categories of reduced multifetal pregnancies. The incidence of intrauterine growth restriction was 19.4% in the nonreduced twins, 36.3% in pregnancies reduced from triplets, 41.6% in pregnancies reduced from quadruplets, and 50% from higher-order multiple gestations. There was a statistically significant trend toward increasing frequency of intrauterine growth restriction with increasing starting fetal number (p = 0.04). The increase in intrauterine growth restriction was primarily accounted for by twin pairs with only one growth-restricted newborn. CONCLUSION: Multifetal pregnancy reduction does not reduce the incidence of intrauterine growth restriction in the remaining fetuses to that of nonreduced twins.     

Intraamniotic infection in patients with preterm labor and twin pregnancies

BACKGROUND: Microbial invasion of the amniotic cavity plays a major role in the pathogenesis of preterm labor and delivery in singleton pregnancy. Nevertheless, this association is not well established among patients with multiple gestations. The purpose of our study was to explore the role of intraamniotic infection in the setting of twin pregnancies. METHODS: Consecutive women with twin gestations, intact membranes and preterm labor who underwent transabdominal amniocentesis under sonographic guidance. Amniotic fluid (AF) was retrieved from both sacs and cultured for aerobic and anaerobic microorganisms as well as for Mycoplasma species. Intraamniotic infection was defined as a positive AF culture for microorganisms. Mann Whitney U test or Student t-test or Fisher's exact test were utilized for analysis. RESULTS: Amniotic fluid was obtained from 74 patients. Sixty-eight women delivered prematurely (91.9%). Amniotic fluid culture results were positive for microorganisms in nine cases and all women with intraamniotic infection delivered prematurely as well as 59 (90.7%) patients with negative culture. Among the nine patients with intraamniotic infection, microorganisms were isolated from the presenting sac in five cases (55.6%), from both sacs in three patients (33.3%) and from the upper sac in the remaining case (11.1%). Patients with a positive AF culture had a more advanced cervical dilatation, a shorter interval amniocentesis-to-delivery and a higher incidence of clinical chorioamnionitis than those with a negative AF culture. CONCLUSIONS: The prevalence of intraamniotic infection and clinical and histological chorioamnionitis in twin pregnancies and preterm labor is similar to singleton pregnancies and preterm labor. Therefore, women with multiple gestations and preterm labor should be managed as singleton pregnancies.     

The work of the American emergency physician

OBJECTIVE: To compare gestational age (GA) calculated from oocyte retrieval and from ultrasound measurements in pregnancies after in vitro fertilization (IVF). DESIGN: In a retrospective study of 253 women with singleton and 84 women with twin pregnancies conceived from IVF, GA calculated from the day of oocyte retrieval was compared with GA calculated in the second trimester of pregnancy from ultrasound measurements of biparietal diameter (BPD) and femur length (FL). RESULTS: For singletons, the mean GA calculated from ultrasound measurements was significantly shorter than the mean GA estimated from the day of oocyte retrieval. The mean difference was 1.9 days (SD 3.3; 95% CI 1.5-2.4) if only BPD was used and 2.1 days (SD 2.1; 95% CI 1.6-2.5) if BPD and FL were combined. For twins, the mean GA calculated from ultrasound measurements was also significantly shorter than the mean GA calculated from the day of oocyte retrieval. The mean difference was 1.4 days (SD 2.7; 95% CI 1.0-1.8) if BPD was used and 1.6 days (SD 2.5; 95% CI 1.2-2.0) if BPD and FL were combined. CONCLUSIONS: In IVF pregnancies, term prediction using ultrasound in the second trimester is reliable and may reduce the number of pregnancies subsequently classified as post-term, thus avoiding unnecessary obstetric interventions.     

A microscopic analysis of cut-bevel versus pencil-point spinal needles

OBJECTIVE: Our purpose was to establish new nomograms for the birth weight of twins on the basis of accurate methods to validate gestational age. STUDY DESIGN: The medical records of 1632 consecutive twin gestations delivered between 1984 and 1996 were reviewed. Only pregnancies induced by ovulation induction techniques or that were measured ultrasonographically for crown-rump length during the first trimester were included. Excluded were those whose fetuses (one or both) were stillborn, or if the mother smoked, had a significant chronic illness, or was prescribed any regular medications. The study comprised 520 twin pregnancies at 28 to 41 gestational weeks at delivery. RESULTS: The median and 10th and 90th percentile birth weight curves were calculated for the studied twins and plotted against previously reported singleton nomograms. Fetuses of twin pregnancies were found to be growth restricted in comparison with previously reported singletons throughout the third trimester. This trend became more evident after the thirty-fourth to thirty-sixth weeks. CONCLUSIONS: We recommend these novel birth weight nomograms for clinical use in the management of twin pregnancies.     

Objectively measured tobacco exposure during pregnancy: neonatal effects and relation to maternal smoking

OBJECTIVES: To measure quantitatively and objectively the maternal and fetal tobacco exposure during pregnancy and its neonatal effects. DESIGN: Tobacco exposure was assessed from maternal serum samples, obtained during the first half of pregnancy and from umbilical serum samples obtained at delivery, by measuring the concentration of nicotine metabolite, cotinine. Data on the respective pregnancies and neonates were collected from the Finnish Medical Birth Registry. SETTING: Finland. SUBJECTS: One thousand two hundred and thirty-seven pregnancies and newborns, representing all pregnancies resulting in a liveborn infant during one week in one country. MAIN OUTCOME MEASURES: Gestational age, birthweight and crown-heel length of newborns. RESULTS: Cotinine (> 6 micrograms/l) was detected in either maternal or umbilical serum in 300 pregnancies, and these mothers and newborns were classified as exposed. Important differences occurred between measured exposure and reported smoking behaviour. Of the exposed mothers, 38% were nonsmokers and 3.4% of the nonexposed mothers were smokers. Tobacco exposure was associated with shorter gestational age, reduced birthweight and shorter crown-heel length of the newborns. After correction for parity, gender, and gestational age, the exposed newborns were on average 188 g (95% confidence interval (CI) 123-253 g) lighter and 10 mm (95% CI 7-13 mm) shorter than the nonexposed newborns. One micrograms/ml of cotinine in maternal serum resulted in a mean decrease of 1.29 g (95% CI 0.55-2.02 g) in birthweight and in a mean decrease of 0.059 mm (95% CI 0.035-0.083 mm) in birth length. Maternal cotinine concentrations better explained the neonatal findings than the reported smoking habits. CONCLUSIONS: There is a quantitative dose and effect relation between tobacco exposure and a decrease in the gestational age at birth and size of the neonate. The smoking habit reported by mothers themselves is not an accurate measure of fetal tobacco exposure.