Pregnancy outcome in Norway after Chernobyl.

Pregnancy outcome has been studied in terms of legal abortions, early spontaneous abortions and total number of pregnancies (in an ad hoc study covering 6 counties) as well as various perinatal health problems (on the basis of routinely recorded data for epidemiological surveillance from the Medical Birth Registry of Norway). Apparently, no effects were observed in terms of an increased occurrence of legal abortions, while spontaneous abortions increased from 7.2% of all pregnancies during the last 12 months before the accident to 8.3% after the accident [corrected]. At the same time, the total number of pregnancies somewhat decreased. Based on monthly measurements in each municipality of external and internal (food-based) doses, dose-response associations were assessed for a number of perinatal health problems. No associations were observed.

PIP: The effects of Chernobyl on pregnancy outcome were investigated in Norway in terms of legal abortions, early spontaneous abortions, total pregnancies, and perinatal health problems (cataracts, microcephaly, low birth weight, and perinatal mortality). The epidemiological results showed that there were no serious gross changes in pregnancy outcome in Norway after Chernobyl in 1986. Anxiety may have led to the temporary decrease in pregnancies. The statistically significant difference in spontaneous abortions between 19867 and 1987, particularly in the months following Chernobyl, may be related but causation cannot be determined based on the present data; i.e., dietary changes due to anxiety may also be related. Further analyses will be conducted with data spanning 5 years after Chernobyl. The Central Bureau of Statistics provided data on legal abortions as reported by hospitals to county medical officers. Spontaneous abortions (16 weeks) are based on ad hoc notifications from hospitals in 5 counties: Aust-Agder, Hordaland, Oppland, Troms, and Trondelag. Compulsory notification of births is recorded in the Medial birth Registry and includes congenital malformations and other perinatal health problems. The National Institute of Radiation Hygiene recorded data after the accident on indoor gamma rates, radiocesium (Cs 134) soil samples, and municipality specific average food-based dose equivalents of Cs 134 and 137 in meat and meat supplies. The total external and internal dose is provided for May 1986-April 1989. Food-based doses remained at an elevated level for an extended period of time. Infant exposure was considered form the 2nd month of gestation. Legal abortions, induced or spontaneous, were not impacted by Chernobyl, but the effect may have been delayed to the 3rd or 4th quarter with a 1.0% increase. However, at Haukeland Hospital in Bergen, the highest abortion rates were 19.1% in 1985-86 and 19.2% in 1986-87. Pregnancies temporarily decreased in the 3rd and 4th quarters following the accident in a period usually reflecting annual increases. Cataract occurrences increased the year after the accident with 8 observed and 3.8 expected, but the P value was insignificant (P=.74). Microcephaly followed a similar pattern. Birth 2500 gms had observed values of 2726 vs. 2639.2 expected, an insignificant P value of .99. Observed perinatal deaths of 634 were less than the 718.8 expected.

Smoking and pregnancy.

Smoking during pregnancy is associated with many adverse outcomes, including fetal and neonatal death. These consequences are tragic in many ways, but perhaps the greatest tragedy is that they are preventable if the smoker ceases to smoke during pregnancy. Although in some instances the so-called constitutional hypothesis is difficult to disprove, the available evidence seems more than convincing that it is smoking itself, and not the smoker's unique constitution, that is responsible. Cessation from smoking is clearly advisable at any time, but more so during pregnancy when every cigarette affects both the smoker and her unborn child.

PIP: This article reviews the literature on the proven and suggested effects of maternal smoking during pregnancy on pregnancy outcomes. Specific areas addressed in relation to smoking are infertility, spontaneous abortion, birthweight, perinatal mortality, malformation, and postnatal effects (sudden infant death syndrome, other respiratory disorders, susceptibility to cancer, growth, and behavior). Estimates of the incidence of smoking during pregnancy in the US have ranged from 35-48%, with an average daily consumption of 10 cigarettes. Study data consistently indicate that smoking during pregnancy is associated with infertility, spontaneous abortion, decreased birthweight, increased perinatal mortality and morbidity, and childhood behavioral problems. Although smoking has been linked with several different physiologic effects, each of which can independently affect development, hypoxia has emerged as a unifying factor. Specifically, decreased oxygenation of the maternal-fetal unit has been noted in complications of pregnancy such as fetal apnea, increased carboxyhemoglobin levels, increased placenta-to-birthweight ratios, placenta previa and abruptio placentae, and reduced uterine and placental blood flow. Another possible mechanism of the effects of smoking during pregnancy involves absorption of cyanide from cigarette smoke. It is stressed that the adverse outcomes associated with maternal smoking during pregnancy are preventable through cessation of the habit.

Pregnancy and lifestyle study: the long-term use of the contraceptive pill and the risk of age-related miscarriage.

Maternal ageing is a very important factor in aneuploidy. It is associated with an increased risk of a liveborn trisomy, especially Down's syndrome, and with a dramatic increase in trisomic conceptions, the majority of which miscarry. A total of 585 volunteer couples who were planning pregnancies participated in a prospective study of reproduction. The couples answered extensive questionnaires and early pregnancy tests (day 28) were conducted each month. The number of years of contraceptive pill use was correlated with pregnancy outcome. Lowered rates of miscarriage were found with increased years of pill use. The cut-off point for this positive effect appeared to be 9 years. Use of oral contraceptives for > or = 9 years was associated with a spontaneous abortion rate of 11.3%, which is about half the rate (23%) which was found in couples who had not used the pill. However, the effect of pill taking was correlated with female age, and when age was examined as an independent factor, the reduction in miscarriage was only statistically significant in women > 30 years old, where the rate of abortion reduced from 28 to 7%. Because age-related aneuploidy in humans probably occurs as a direct or an indirect result of follicle depletion, it is proposed that the long-term use of the oral contraceptive pill protects against abortion due to aneuploidy by preserving the number of follicles.

PIP: The impact of oral contraceptive use on ovarian follicular dynamics--considered to be a key determinant of trisomic conceptions--was investigated in a prospective study of 585 Australian women who were planning pregnancy. Urine samples were collected on the last day of each menstrual cycle in which conception was attempted; outcomes were classified as live birth of a normal infant, spontaneous abortion, or persisting infertility. Only 39 women had never used oral contraceptives (OCs); the majority had used the pill for at least six months. The age-related miscarriage rate was 13.4% in women aged 25-29 years, 17.3% in those aged 30-34 years, and 28.3% in those aged 35-39 years. The frequency of miscarriage showed a pattern of decline with increasing years of OC use: 0-2, 22.2%; 3-4, 17.3%; 5-6, 19.6%; 7-8, 16.7%; and 9 or more, 11.4%. However, the addition of maternal age to the logistic regression model revealed that the association between OC use duration and miscarriage was significant (p 0.001) only for women 30 years of age and over. In this latter group. the mean miscarriage rate decreased from 28% with 0-2 years of OC use to 7% with 9 or more years of use. It is hypothesized that the decrease of about 15% in the rate of miscarriage among longterm pill users aged 30 years or over is attributable to OC-related preservation of ovarian follicles and a subsequent reduction in spontaneous abortion due to aneuploidy--a defect related to pre-menopausal declines in follicle numbers.