Decrease in severity of intrauterine growth retardation in subsequent pregnancies

Characteristics in the first vaginal birth and their association with mode of delivery in the subsequent birth

BACKGROUND

The extent to which complications or adverse outcomes in a first vaginal birth may contribute to mode of delivery in the next birth remains unclear. This study examines the impact of the first birth on subsequent mode of delivery.

METHODS

The study population included women with a first vaginal birth and a consecutive second birth. Data were obtained from linked birth and hospital records for the state of New South Wales, Australia 2000-09. The primary outcome was the mode of delivery for the second birth. Planned caesarean was modelled using logistic regression; intrapartum caesarean and instrumental delivery were modelled using multinomial logistic regression.

RESULTS

Of the 114 287 second births, 4.2% were planned caesarean, 3.0% were intrapartum caesarean and 4.8% were instrumental deliveries. Adjusted risk factors from the first birth for a planned second birth caesarean were third to fourth degree tear [odds ratio (OR) = 5.0 [95% confidence interval (CI) 4.6, 5.4]], severe neonatal morbidity (OR = 3.2 [95% CI 2.9, 3.6]), perinatal death (OR = 3.2 [95% CI 2.3, 4.4]), severe maternal morbidity (OR = 2.8 [95% CI 2.3, 3.3]), instrumental delivery, large infant, labour induction, epidural use, use of oxytocin for augmentation and episiotomy. Important risk factors (OR > 2) for intrapartum caesarean in the second birth were perinatal death or severe neonatal morbidity in the first birth. Risk factors for instrumental delivery in the second birth were perinatal death, preterm delivery and instrumental delivery.

CONCLUSIONS

Obstetrical interventions and adverse pregnancy outcomes in the first birth were associated with increased risk of operative delivery in the second birth.

Fetal growth restriction and subsequent pregnancy risks

Fetal growth restriction can result from a variety of intrinsic or extrinsic insults, resulting from maternal, fetal, and placental factors. Determining the underlying cause of poor fetal growth can be difficult but is essential for assessing potential risks for future pregnancies. Importantly, recurrence risks greatly depend on these underlying conditions. Understanding these risks can allow more appropriate patient counseling and may influence management strategies to optimize future pregnancies.

Low birthweight and mortality: the tendency to repeat low birthweight and its association with early neonatal and infant morbidity and mortality

Previous studies have demonstrated the tendency to repeat gestational age and birthweight in successive pregnancies and that this tendency is associated with infant survival. Thus, newborn outcome and survival is less favourable if the gestational age and size departs from this maternal tendency. This paper aims to study diseases or conditions that might be associated with this effect. Data were provided through a linkage between three Danish health registries: the Danish Fertility Database, the National Hospital Registry, and the Registry for Preventive Medicine. Such linkage was possible due to the use of unique ID-person numbers. The study included all 8219 second-order low-birthweight (LBW) singleton Danish births, 1980-94, of whom 7811 were liveborn. It was also required that the mother's first delivery took place during that period. The analysis considered 7803 of these births; eight were excluded due to insufficient information. Of the second-order LBW children, 26% had an elder sibling who was also LBW. Early neonatal mortality of a 'non-repeat' LBW birth was 1.3 times higher than 'repeat' LBW births [53.8 vs. 41.2 per 1000; RR 1.31; 95% CI 1.03, 1.65], as was infant mortality [78.4 vs. 60.8 per 1000; RR 1.30; 95% CI 1.06, 1.56]. Also, proportionately more LBW repeat births had Apgar scores of >or=7 after 1 and 5 min. Overall, repeat second-order LBW babies weighed 68 g more than non-repeat LBW babies (P < 0.001). At term, the weight difference was 160 g higher among repeat LBW births (P < 0.001). The mean number of hospitalisations during the first year of life was lower among repeat than non-repeat LBW babies (2.30 vs. 2.46, P < 0.001), while the mean duration of stay was 23.71 vs. 23.97 days (P > 0.05). Newborn immaturity was the most common diagnosis for hospitalisation, and infections the second most common. There were no differences between repeat and non-repeat LBW births in the proportion with each diagnosis. Apart from the differences in birthweight, we were unable to explain the improved survival for repeat compared with non-repeat LBW babies. Except for differences in Apgar scores, we observed no differences in morbidity based on registered hospitalisations during infancy.

[Genes and intra-uterine growth retardation]

Genetic analysis of growth from birth to adulthood shows the existence of a strong genetic component in the variance of size at particular milestones in the growth process, such as height at take-off, at peak velocity and at adulthood. While it is well known that postnatal growth is strongly genetically determined, the importance of genes in normal variations of prenatal growth is less known. Genetic analysis of prenatal growth in human is not an easy problem and weighing the genetic and non-genetic component in intra-uterine growth retardation an almost impossible task. It is now well known that adults who had a low birthweight or who were thin at birth, with a low ponderal index, tend to be insulin resistant and have an increased risk of developing non-insulin-dependent diabetes mellitus later in life. According to the thrifty genotype hypothesis, genes predisposing to type 2 diabetes mellitus are very likely to have been survival genes for our ancestors, helping them to store energy during long periods of starvation. Both epidemiological surveys of adults born after prenatal exposure to exposure to famine and biochemical investigations of insulin resistance in low birthweight children show that the association between a low birthweight and an increased risk of developing type 2 diabetes mellitus later in life has a genetic basis. While low birthweight infants have a decreased survival probability in infancy, having a small baby may have been a selective advantage during long periods of starvation. This could explain why the same genetic variants cause low birthweight phenotype and insulin resistance predisposing to non-insulin-dependent diabetes.