Risk factors associated with intrauterine growth restriction (IUGR) have previously been identified, but few studies have described the relationship between IUGR and maternal stress caused by exposure to civil unrest. Here, we investigate this relationship during the Mount Elgon crisis in western Kenya between 2006 and 2008, following a period of violence. Birth weight data were compared between three hospitals in an exposed area, Mount Elgon (n=570), and one hospital in a control area, Kimilili (n=530). In a sub-analysis, the most stress exposed hospital, Bungoma West (n=211), was compared with the control hospital in Kimilili. Adjustments were made for offspring sex, gestational age and parity. The difference in mean birth weight between the most stress-exposed hospital (Bungoma West) and the control hospital (Kimilili) was 91 g after full adjustment (P=0.041). In conclusion, epidemiological data suggest a significant relationship between exposure to civil unrest and IUGR causing lower birth weight.

The retardation of fetal growth in twin as compared to singleton gestations may be due to maternal and/or placental factors. The separate birthweights and related placental weights of 487 dichorial twin pairs were recorded, and the heavier placental weights of firstborns in comparison with second-borns were found to be related to the heavier birthweights of firstborns compared to second-borns. The lighter placental weights of firstborns compared to second-borns were found to be related to the lighter birthweights of firstborns compared to second-borns. Obviously, the placenta itself may may very well be the cause of the retardation of fetal growth in twin gestations.

The present study aimed at clarifying the characteristics of twins' physical growth. First, 557 pairs of normal Japanese twins were analyzed according to the following three life stages: (1) intrauterine growth, (2) body weight and height from birth to 6 years, and (3) body weight and height at school age (from 6 to 11 years). The following results were obtained. 1. Intrauterine growth of twins was very different from that of singletons, especially as regards weight, so twins should be estimated by twin standards. 2. Size deficit at birth was appropriately recovered over the first 6 years. 3. No size deficit was observed by school age. Second, the similarity of bodyweight and height according to zygosity was analyzed using 605 pairs of normal Japanese twins, 427 monozygotic (MZ), 113 same-sexed dizygotic (DZ) and 65 opposite-sexed DZ pairs. The similarity between MZ and DZ pairs was almost the same at birth. However, MZ pairs became increasingly more similar with age, whereas DZ pairs became more dissimilar. This tendency was very clearly seen through early infancy, thus suggesting that genetic factors became more apparent during this life stage.

The birthweights and placental weights of 3000 singletons, 1500 twin pairs and 67 triplets are studied in relation to the gestational age. From 30-32 weeks onwards, newborns of twin- and triplet gestation show lower birthweight as compared to singleton newborns. Placental indices (placental weights related to birthweights) are about alike in singletons, twins and triplets. From about 24 weeks onwards placental weights of twin and triplet newborns are smaller as compared to those of singletons. Obviously, children in multiple gestations become growth retarded, preceded by and very likely due to poor early placental development (placental crowding of the uterus).

In addition to centile curves for birth weight and height of single infants, the authors offer similar biometric references for twins derived from a large French data base. The aim of the work is to assist in discovering small-for-date twins. In the actual prenatal environment, the curves show a decrease in the evolution of these growth parameters in comparison with the single pregnancy standards as early as the 30th week of pregnancy.