A study was conducted on twinning in relatives of consecutive triplet sets in the Åland Islands in the years 1740-1939. The incidence of twinning in sibships of triplets was extremely high, 80/1000 (56/1000 before and 143/1000 after the triplet maternity). In Finland as a whole, 1905-1954, the twinning rate was among mothers of triplets 38/1000, ie, about 2.6 times the rate in general population, and was higher after (48/1000) than before the triplet maternity (34/1000). In the sibships of fathers of triplets there was a low rate of twinning (below 10/1000) both of same-sexed (SS) and of opposite-sexed (OS) triplets. Among sibships of mothers of OS triplets the twinning rate was 18/1000 and among mothers' sibships of SS triplets 26/1000. The series of triplet families from both Åland and Finland as a whole indicate a considerably higher frequency of twinning on the maternal than on the paternal side. The sibships of OS triplets in Finland have higher twinning rates than sibships of SS triplets (50/1000 vs 27/1000). In sibships of triplets, not only the DZ but also the MZ twinning rates were approximately twice as high as those in the general population. The triplet rates in Finland were increasing strongly with maternal age and were in the last century among mothers of 30-39 years of age considerably higher than among mothers from this century. This, in combination with higher mean parity, may explain the high rates of multiple maternities in sibships of triplets in the past. The rate of triplet maternities seems to be more sensitive to sociodemographic changes than the rate of twin maternities. Mothers of triplets in Finland had a high frequency (more than 40%) of prenuptially conceived firstborn children. This, and a short protogenesic interval indicate that triplet-prone mothers are more fecundable, ie, they conceive with greater ease and/or may have a better physical condition than other women for completing a gestation with multiple embryos.

Multiple birth rates in entire Japan were analyzed using vital statistics for 1951 to 1988. The triplet rate was nearly constant from 1951 to 1974, where the rate per million births was 58, then increased with the year up to 1982 (104), and decreased up to 1984, and suddenly increased thereafter (109 in 1987). The average rate of quadruplets per million births from 1951 to 1968 was 0.93, then increased with the year up to 1975 (7.5), and decreased until 1984 and suddenly increased thereafter (10.6 in 1987). The rate of quintuplets was 0.77 per million births during the period from 1975 to 1987. The higher multiple birth rate since 1975 was attributed to the higher proportion of mothers treated with ovulation-inducing hormones in Japan. Since 1985, higher multiple birth rates might be partially attributed to in vitro fertilization. The stillbirth rates for male triplets gradually decreased from 1960 to 1978 and thereafter remained constant at a little higher level except in 1988, whereas the rates for females gradually decreased with the year. The overall stillbirth rates decreased to 1/4 for triplets and to 1/5 for quadruplets during the 37-year period from 1951. The overall stillbirth rate of quintuplets was 0.60 (51/85) during the period 1975-1987.

In an attempt to improve our understanding of the factors that affect human twinning, we further developed the models given by Hellin (1895) and Peller (1946). The connection between these models and our own model (“Fellman's law”) were studied. These attempts have resulted in a more general model, which was then applied to data from Åland Islands (1750-1939), Nîmes (1790-1875), Stuttgart (about 1790-1900) and Utah (1850-1900). The product of the mean sibship size and the total twinning rate can be considered as a crude estimate of the expected number of sets of twins in a sibship. The same can be said about the twinning parameter in our model. These estimates are in good agreement. If we consider twinning data only, we obtain the geometric distribution, and log (Nk), where Nk is the number of mothers with k twin maternities, is a linear function of the number of recurrences. Graphically, this property can easily be checked. For sibships containing three or more sets of twins, all four populations show higher values than expected, particularly the populations from Stuttgart and Utah, which data also show poor agreement according to a χ2-test. A more exact model would demand more detailed demographic information, such as distribution of sibship sizes, age-specific twinning rates and temporal variations in twinning.

The osberved number of mothers in Åland with several recurrences of multiple maternities shows a considerable excess over the expected number as predicted by Peller's rule. The parameters in our model can be estimated by the maximum likelihood method and the obtained model fits the data better then Peller's model.

The dizygotic twinning rate in Italy, adjusted for maternal age and parity, declined from 8.9/1000 in 1949-1953 to 6.0/1000 in 1978-81, but may have stabilized or recovered slightly in the early 1980s. The long decline was greatest in the oldest mothers, and the recent increase, if any, has been principally in first births and in women under 30. The monozygotic rate rose from 3.8/1000 in 1969-73 to 4.3/1000 in 1982-85, having been relatively stable prior to that period. No good explanation for these trends is apparent.

A case-control study was conducted to evaluate the association between maternal age and parity and dizygotic (DZ) and monozygotic (MZ) twinning, respectively. Mothers of all twins born alive in Denmark in 1984 or 1985 were included into the study as cases, and a random sample of mothers of singletons were controls. Data on maternal age at delivery and number of previous births were collected from the Danish Medical Birth Register. By means of logistic regression analysis, a significant and positive association was found betwen maternal age and DZ twinning, and a significant and negative association between parity and MZ twinning. No association was found for parity and DZ twinning, nor for maternal age and MZ twinning. The study suggests that human MZ twinning has predictors too, as has DZ twinning. The finding has implications for zygosity classification in future twin research.

In order to investigate changes in twinning rate during World War II and postwar years, when the people in Tokyo suffered from malnutrition, about 80,000 delivery records during 1924-86 at one hospital in downtown Tokyo were examined. The twinning rate decreased from 1.47% in the 1920s to 0.81% in the 1980s. During the 1940s, the rate was 1.03% for 1940-42 and 0.94% for 1948-49, but it dropped down to 0.70% for 1943-47. In 1945, when Tokyo was heavily bombed repeatedly to be burnt out, and the people suffered from severe malnutrition, only one case of twinning was found among 305 maternities at this hospital (0.33%). While the mean birth weight of term singleton babies was 2953 g in 1940-41, it decreased to 2918 g in 1943-47, especially to 2856 g in 1945. This change in birth weight evidenced that the nutritional conditions in Tokyo became worse in 1943-47. This report suggests that the twinning rate decreased also during this period in Tokyo when the people suffered from malnutrition.

Ultrasonographic examinations were performed on 519 pregnant women in the first trimester at three hospitals in Tokyo from August 1985 to March 1987. Among 519 women, two fetal heart movements (FHMs) were comfirmed in six cases. In two of these six cases, one of two FHMs disappeared two weeks later, and these were considered the “vanishing twin”. In eight cases among those with ultrasonographic image of echo-free-space (EFS) in the uterus, the observed EFS was considered to be a probable empty gestational sac (GS-like-EFS-image). Seven of eight GS-like-EFS-images were observed in October-December (p < 0.01) and two “vanishing twin” cases were also observed in the same season. Spontaneous abortion occurred in 11 cases and these were also more frequently observed in October-November (p < 0.05). Some abortive factor is supposed to have prevailed in October-December. All six women having twin fetuses (including the “vanishing twin” cases) were born in January-May (p < 0.05) and those having GS-like-EFS-images or terminating their pregnancy in spontaneous abortion were also born more frequently in the same season. Twin-prone and abortion-prone characteristics of the women born in this season are considered.

Source of data is “Survey on Socio-Economic Aspects of Vital Events – Plural Births in 1975”, including 12,392 twin pairs, 124 triplet sets, 7 quadruplet sets and 1 quintuplet set. Feal deaths were 3,285 for twins, 141 for triplets, 17 for quadruplets, and 5 for quintuplets, among which the numbers of birth defects were 78, 3, 0, and 0, respectively. Concordant twin pairs with the same category of birth defect were 20 among 56 pairs (0.36). As for the remaining 36 pairs, 2 pairs had different category of birth defects, 27 pairs had liveborn cotwins, and 7 pairs were both fetal deaths among which a twin had birth defect. The second-born twins had birth defects more frequently than the first-born twins among fetal deaths (28 vs 6).

This article discusses the following areas of interest related to the obstetric care of multiple pregnancy: 1) methods of diagnosis and ultrasound, 2) pregnancy protection through adequate maternal nutrition, 3) mode of delivery, 4) discordant twins, and 5) assisted reproductive technology. The article also emphasizes the FIGO/WHO concerns regarding safe motherood and proposes a four point program to reduce perinatal death rates in multiple pregnancy. These elements are: 1) adequate primary health care including access to family planning information and technology, 2) prenatal care with referral of high risk patients to specialized centers, 3) the presence of trained personnel for all women in childbirth, 4) effective access to obstetric care for women who are pregnant, giving birth, or recently delivered.

As an extension of previous work on the risk of prematurity in singletons and on the social cost of twin births, an analysis has been carried out into the cost effectiveness of preventing premature delivery in twin pregnancies. The cost of prevention is assessed in terms of early diagnosis through ultrasound screening and of an extra 11 weeks of work leave to expectant mothers. When this cost is compared to the social cost involved in the transfer of newborns to neonatal intensity care units and in supporting handicapped children, it is concluded that the total cost of prevention corresponds to one-third of the long-term costs associated to lack of prevention.

Within the same in vitro fertilization (IVF) program, treatment trials leading to single and multiple ongoing gestation were compared. Rates of cesarean delivery, prematurity and perinatal mortality were found much higher among twin and multiple IVF pregnancies. Our work thus attempts at defining characteristics of proneness to multiple gestation in IVF treatment, in order to try and avoid its occurrence. The mean vitality score of embryos replaced is the most reliable criterion for this purpose, enabling one to replace no more than two embryos when the average score is high. Age of the patient and cause of infertility are almost nondiscriminant in this respect. Ovarian stimulation parameters such as total dosage of gonadotropin treatment and level of estrogenic response, as well as numbers of oocytes and embryos obtained, may serve as secondary criteria for assessing the twinning risk.

Current antenatal technologies have improved the obstetrician's ability to assess fetal well-being as well as to diagnose fetal compromise. These technologies have given rise to very difficult ethical issues in the management of compromised twin pregnancies: for example, a choice must be made between putting a healthy twin at risk due to preterm delivery for the sake of a compromised cotwin or of allowing the compromised twin to die in order to buy time for the healthy twin. Though each case is unique, good medical practice requires a standard of care by which consistent patient management can be proposed. In the pluralistic environment of Northwestern Memorial Hospital, our staff has favored a standard of care based on patient autonomy. This approach demands: 1) a practitioner who offers a thorough explanation of the diagnosis and possible treatment approaches; 2) time for the patient and her partner to assimilate this information and test treatment options against their personal value system; 3) a third, but disinterested, party to facilitate patient understanding and value clarification; 4) a practitioner either willing to support the patient's decisions or refer her to another practitioner who will.

It has been suggested that the surviving cotwin and the mother are seriously affected when intrautrine fetal death of one monozygotic twin occurs. Several authors have reported brain damage in the surviving twin coexisting in utero with dead monozygotic cotwin. Most of such instances are monochorionic and show vascular communication between paired twins in the placenta. In a total of 133 pairs of monochorionic twins, death of one twin during pregnancy occurred in 33 cases (24.8%). Of 33 surviving twins, 8 babies suffered from porencephaly, cerebral palsy and other abnormalities. More unfavorable prognosis was recognized when a cotwin died in the latter half of pregnancy, while when a monozygotic cotwin died in the early stage of pregnancy, the surviving twin uneventfully grew to term in most cases.

A case is reported of a transfusion syndrome in a triplet pregnancy with intrauterine death of two of the fetuses. This is an exceptional occurrence in a triplet pregnancy and raises the problem of the management of multiple pregnancies associated with the death of one or more of the fetuses. The problem of the method of delivery and the complications arising in triplet dizygotic pregnancies is discussed.

Ultrasonic assessment of fetal weight derived from multiple measurements of the fetus has become accepted in clinical practice as being useful in singleton pregnancies. Several different formulae for estimating fetal weight have been derived from differing measurements of the fetus, such as biparietal diameter, trunk circumference, and femur length. To date, there has been no attempt to evaluate such a technique in multiple pregnancy. This study aims to see whether the formulae derived for singleton pregnancy are applicable to twin pregnancies. Estimated fetal weight will be derived by mathematical modelling from ultrasonic measurements made within a week of delivery and the results compared with the actual birthweight to give an indication of how good such estimated fetal weights are. Factors to be considered in the analysis include whether there are differences between Twin I and Twin II, differences of presentation with twins and differences by gestation at delivery.

The aim of this study on all twin births in Sweden between 1973 and 1985 was to evaluate the effect of maternal age, parity, and sex on twin perinatal mortality (PNM), by using national data held at the Medical Birth Registry, National Board of Health and Welfare, Stockholm. Zygosity in this study was estimated by the Hardy-Weinberg formula. In all, 22,374 twins were born; 972 (4.3%) of these died perinatally. The relative risk for perinatal death (after standardization for maternal age, parity, and like sex) decreased significantly during the study period, and reached its lowest value (0.3) in 1983. Maternal age was not associated with PNM, while women having their first delivery had a significantly higher PNM than the rest of the parturients. The MZ twinning rate increased fom 0.36% during 1973-76, to 0.40% during 1977-81 and 0.44% during 1982-85 (trend analysis: χ2 = 40.1, p < 0.001). After stratification for year of delivery and birthweight, like-sexed twins had a significantly higher PNM than unlike-sexed twins (odds ratio, OR = 1.25, 95% confidence interval, CI = 1.02-1.54). Males had a significantly higher PNM than females in like-sexed pairs (OR = 1.39, 95% CI = 1.16-1.66), and in unlike-sexed pairs (OR = 1.46, 95% CI = 1.01-2.10). MZ twins had a significantly higher estimated PNM than DZ ones (OR = 1.31, 95% CI = 1.02-1.67).

This study showed that biological handicap with many complications at birth was much more recognized in the second-born than in the first-born twins. One of the most prominent intrapair differences was, for example, the weight at birth. However, intrapair differences, which were observed also in other physical measurements, diminished gradually with age. Moreover, as for intellectual ability, which was represented by the scores of the entrance examination test or standard achievement test, no remarkable influences due to handicap of the second-born were identified. Thus, it was concluded that the biological handicap seen in the second-born twin at birth did not give any significant effect on later development.

Preterm deliveries in singleton pregnancies have been shown to be associated with decreased rate of growth in utero. A total of 113 sets of twins were scanned serially at fortnightly intervals to establish fetal growth. There was no significant difference in the growth pattern in twins delivered before 37 weeks compared to those delivered after this time.