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Biomedical subjects

P A Lancaster

Publications and source records attributed to P A Lancaster.

At least 19 recordsLinked to original sources
PubMed1992

Absence of limbs and gross body wall defects: an epidemiological study of related rare malformation conditions.

The study is based on almost 10 million births and reports on 215 infants with two unusual malformations: amelia and gross body wall defect. Amelia without body wall defect was present in 116 cases, 67 had body wall defects without amelia, and 32 had both. The total rate was 2.2 per 100,000 births. The infants were divided into five mutually exclusive groups. There were 40 infants (0.4 per 100,000) with agenesis of the body stalk, 18 with amelia and other types of gross body wall defects (0.2 per 100,000), 56 with amelia and malformations other than gross body wall defects (0.6 per 100,000), 41 with amelia (with or without other limb reduction defects) but no nonlimb malformations (0.4 per 100,000), and 60 infants with gross body wall defects of a type other than agenesis of body stalk and without amelia (0.6 per 100,000). A weak trend of decreasing prevalence of these malformations was found during the observation period. Infants with agenesis of the body stalk and infants with amelia combined with other types of gross body wall defects occurred at an increased rate in infants of young women. This maternal age effect is also found with gastroschisis, but not with omphalocele, and may indicate etiological or pathogenetic similarities between gastroschisis and the two former groups of defect. In infants with amelia, additional limb reduction defects could be of any type: transverse, longitudinal, or intercalary. Therefore, amelia may be the end result of different types of disturbances of limb morphogenesis. There was an increased rate of twinning. The relationship with amniotic band syndrome is discussed.

Abdominal Muscles↗
PubMed1992

An international case-control study on hypospadias. The problem with variability and the beauty of diversity.

The paper describes problems and advantages in an international cooperative study of a case-control design, aimed at investigating the possible association between exogenous hormones and hypospadias. The varying degrees of the ascertainment of specific exposures and risk factors, in spite of the use of a standardized questionnaire is illustrated. Definite support for the existence of recall or interviewer bias is presented. On the other hand, the multipopulation design offers possibilities to make use of the diversity of the populations: differences in reproductive patterns and in specific exposures such as drug use, smoking and maternal occupation.

Bias↗
PubMed1992

Increased pregnancy failure rates after clomiphene following assisted reproductive technology.

The obstetric outcome of 1941 in-vitro fertilization (IVF) and 1436 gamete intra-Fallopian transfer (GIFT) pregnancies reported from 25 units in Australia and New Zealand have been reviewed. Recently, gonadotrophin-releasing hormone analogues (GnRHa) have replaced clomiphene as part of many ovarian stimulation protocols. Clinical abortion rates after clomiphene (24.4% for IVF; 23.0% for GIFT) were not significantly higher than after GnRHa (20.7% for IVF; 17.9% for GIFT) when IVF and GIFT data were considered separately. However, the abortion rate for combined IVF and GIFT was significantly higher after clomiphene than after GnRHa. This pattern was found for most maternal age groups and causes of infertility although differences were not significant in all categories. The combined IVF and GIFT ectopic pregnancy rate of 6.7% for clomiphene was significantly higher than 4.1% for GnRHa. Because the mechanism of action of clomiphene for oocyte recruitment during folliculogenesis means that GnRHa cannot be used with clomiphene, luteinizing hormone (LH) levels are higher in clomiphene cycles than in GnRHa cycles. Clomiphene itself could cause the increase in pregnancy wastage or increased levels of LH during follicule genesis associated with the use of clomiphene may cause the observed pregnancy failures.

Abortion, Spontaneous↗
PubMed1992

The cyclops and the mermaid: an epidemiological study of two types of rare malformation.

Infants with cyclopia or sirenomelia are born at an approximate rate of 1 in 100,000 births. Eight malformation monitoring systems around the world jointly studied the epidemiology of these rare malformations: 102 infants with cyclopia, 96 with sirenomelia, and one with both conditions were identified among nearly 10.1 million births. Maternal age is somewhat increased for cyclopia, indicating the likely inclusion of some chromosomally abnormal infants which were not identified. About half of the infants are stillborn. There is a female excess among infants with cyclopia. Excess twinning occurred for cyclopia and possibly also for sirenomelia. An analysis of associated malformations indicates the similarity between the two conditions, which is in agreement with recent embryological analysis.

Abnormalities, Multiple↗
PubMed1991

Parental fertility and infant hypospadias: an international case-control study.

The authors have performed an international case-control study on the significance of exogenous hormones for the origin of hypospadias (Källén et al., 1991 a,b). Using data from this study on 846 infants with isolated hypospadias and equally many controls (next male infant born in the same hospital as the case), variables that might indicate an increased rate of fertility problems in couples who had a boy with hypospadias were studied. Cases had slightly fewer previous pregnancies, there was practically no difference in the rate of previous induced abortions, and no demonstrable difference in menstrual history. Infertility periods of at least 6 months were more likely among cases than controls but the difference did not reach statistical significance in a two-tailed test. There was no demonstrable difference in the time to conceive between cases and controls. The difficulties of directly studying subfertility problems are stressed.

Case-Control Studies↗
PubMed1991

Oral contraceptives in the etiology of isolated hypospadias.

With the objective of identifying whether hypospadias in infants is associated with maternal use of oral contraceptives before pregnancy or in early pregnancy, 846 case-control pairs were collected from eight different malformation monitoring programs around the world and mothers were interviewed using structured questionnaires administered after the birth of the infants. There was no difference in the preconceptional use of oral contraceptives between cases and controls, neither with respect to the number of years of oral contraceptive usage nor the time between stopping oral contraceptives and the present pregnancy. To this material was added data on oral contraceptive usage in early pregnancy from two other sources: an ongoing case-control study in Spain (725 infants with hypospadias) and a population-based study in Sweden (631 infants with hypospadias). There was no statistically significant difference in oral contraceptive exposure in early pregnancy between cases and controls. There is no demonstrable association between oral contraceptive use and infant hypospadias.

Contraceptives, Oral↗
PubMed1991

Assisted conception. Health services and evaluation.

Comparison of assisted conception in Australia, the United Kingdom, and the United States indicates that further rapid growth in services is likely in many countries. Better data on pregnancy rates and the outcome of pregnancy, as well as standardized reporting of national results, are needed to monitor the effectiveness of treatment.

Australia↗
PubMed1989

Indicators of social class--relationship between prestige of occupation and suburb of residence.

The difficulty of measuring social class is well known. Two indicators of social class, prestige of occupation and prestige of suburb of residence, are considered here. Australian prestige scales which measure these indicators are discussed. Comparisons between the original scales and the recently updated versions indicate that in the Australian community there is general community agreement on the prestige of occupations and of suburbs which has changed little over two decades. However, there is only a weak association between the prestige of the occupation in which a person is employed and the prestige of the suburb in which that person resides. This raises queries concerning the validity of using prestige of suburb as an indicator of social class, and highlights the fact that when conducting research one indicator of social class cannot simply be substituted for another. The implications for investigation of health-related issues are discussed.

Australia↗
PubMed1986

The secular trend of twinning in Australia, 1853-1982.

The incidence of twinning in Australia from 1853 to 1982 is described. The overall trend was determined by changes in the dizygotic rate and, for more than a century, it has been similar to that found in Finland and the South of Italy. It is not explained by demographic changes and there is no clear relationship with industrialisation or psychosocial factors. Monozygotic twinning has increased, most markedly in the 1970s. No adequate explanation has been given for this increase, so continuing surveillance in many different populations is necessary.

Age Factors↗
PubMed1986

Health registers for congenital malformations and in vitro fertilization.

Registers of reproductive outcomes can be used to obtain information about the incidence of health problems related to pregnancy and to study associated risk factors and underlying causes. In Australia, a national data system for congenital malformations, based on multiple sources of notifications, has provided data to determine the incidence of major malformations over a 3-year period (1981-1983) and to study regional variations in incidence possibly due to environmental or other teratogens. A national register of pregnancies resulting from in vitro fertilization (IVF) has been established by obtaining reports from IVF units for pregnancies completed by the end of 1983. This register, developed in collaboration with the Fertility Society of Australia, has been used to describe the characteristics of infertile couples and the management of IVF pregnancies and to determine the incidence of pregnancy losses and major congenital malformations. Confidentiality issues were important in setting up both data systems.

Adult↗