Maternal and fetal genetic contribution to gestational weight gain

BACKGROUND

Clinical recommendations to limit gestational weight gain (GWG) imply high GWG is causally related to adverse outcomes in mother or offspring, but GWG is the sum of several inter-related complex phenotypes (maternal fat deposition and vascular expansion, placenta, amniotic fluid and fetal growth). Understanding the genetic contribution to GWG could help clarify the potential effect of its different components on maternal and offspring health. Here we explore the genetic contribution to total, early and late GWG.

PARTICIPANTS AND METHODS

A genome-wide association study was used to identify maternal and fetal variants contributing to GWG in up to 10 543 mothers and 16 317 offspring of European origin, with replication in 10 660 mothers and 7561 offspring. Additional analyses determined the proportion of variability in GWG from maternal and fetal common genetic variants and the overlap of established genome-wide significant variants for phenotypes relevant to GWG (for example, maternal body mass index (BMI) and glucose, birth weight).

RESULTS

Approximately 20% of the variability in GWG was tagged by common maternal genetic variants, and the fetal genome made a surprisingly minor contribution to explain variation in GWG. Variants near the pregnancy-specific beta-1 glycoprotein 5 (PSG5) gene reached genome-wide significance (P=1.71 × 10-8) for total GWG in the offspring genome, but did not replicate. Some established variants associated with increased BMI, fasting glucose and type 2 diabetes were associated with lower early, and higher later GWG. Maternal variants related to higher systolic blood pressure were related to lower late GWG. Established maternal and fetal birth weight variants were largely unrelated to GWG.

CONCLUSIONS

We found a modest contribution of maternal common variants to GWG and some overlap of maternal BMI, glucose and type 2 diabetes variants with GWG. These findings suggest that associations between GWG and later offspring/maternal outcomes may be due to the relationship of maternal BMI and diabetes with GWG.

Role of adipokines in obesity-associated hypertension

It has been well documented that obesity is a major risk factor for the development of the hypertensive state. The correlation between body mass index and blood pressure level is well established. Nevertheless, the exact mechanisms which contribute to obesity-related hypertension remain poorly understood. In the last years, we have realized that the white adipose tissue is not just an inert organ for nutrient storage and isolation but rather depending on the body mass index the biggest endocrinological organ. Thus, the possible contribution of adipokines to the blood pressure elevation becomes an attractive hypothesis to explain the hypertensive state that often occurs in obesity. In this review, we consider direct and indirect effects of main adipokines on structural and functional changes in the cardiovascular system.

High birth weight, asthma and atopy at the age of 16 yr

The association between high birth weight and asthma has been suggested. The Northern Finland Birth Cohort 1986, a longitudinal cohort originally including 9479 participants, has been followed up since birth until the age of 16 yr. Using the data of this study, we analyzed the association of high birth weight with asthma and atopic sensitization at the age of 16 yr. The analysis included the 5995 subjects with complete skin prick test data and the 5500 subjects with data on doctor-diagnosed asthma (written questionnaire) at the age of 16 yr. Atopy was defined as at least one positive skin prick test reaction, which definition was also used to separate atopic and non-atopic asthma. There was a significant association between high birth weight (>4510 g) and asthma among the atopic subjects (OR 2.40, 95% CI 1.33-4.32). When looking at atopy, the highest risk was observed among the subjects with highest birth weight category (>4510 g) (OR 1.44, 95% CI 1.05-1.97) and the adjacent (4200-4500 g) birth weight category (OR 1.24, 95% CI 1.01-1.53), when compared with the reference category (2500-3340 g). Our results support the notion that high birth weight is associated with an increased risk of asthma and suggest that the association is mostly explained by an increased risk of atopy. The biological mechanisms behind the associations are unknown, but they could be related to obesity.

Conditions for paediatric hearing screening: a survey in 28 Finnish child welfare clinics

The present Finnish paediatric hearing screening programme was assessed by interviewing nurses and doctors in 28 child welfare clinics responsible for the hearing screening of 18,500 preschool children. Practical issues which might have effects on both performing the screenings and referring the children with abnormal screening results were emphasised. This survey brought out a great variety of deficiencies, which may contribute to the existing delayed diagnosis of hearing impairments. Hearing screening was routinely done 4-12 times per child before school age, instead of the 3 times recommended. Methods with a nonspecific frequency range and sound pressure level were often used. Audiometers were only used in 22 of the 28 clinics, and in only 9 clinics were the audiometers calibrated yearly. The median time of working in the child health care field at that particular health centre was 7 y for the nurses and 6 y for the doctors. Both the nurses and the doctors had numerous responsibilities other than paediatric hearing screening. Implementation of an updating training programme in paediatric audiology for the personnel is recommended.

More education in paediatric audiology needed for child welfare clinic nurses and doctors

Opinions on formal and further education in paediatric audiology were surveyed by interviewing nurses and doctors in 28 Finnish child welfare clinics. Over half of the nurses recalled that they had been taught hearing screening during their period of practical training. Regarding formal teaching in paediatric audiology, the majority of doctors referred to courses in either otolaryngology, paediatrics or both. None of the doctors and only three of the nurses had taken part in any updating courses dealing with paediatric audiology during the last three years, and it turned out that no such courses had been arranged in three of the five hospital districts. However, 17 out of the 27 doctors and 23 out of the 28 nurses expressed their interest in further education. The present amount of formal education in paediatric audiology was ascertained from all five Finnish medical faculties and the five nursing schools in the provinces of Oulu and Lapland. The university departments of otolaryngology carry the major responsibility for teaching in paediatric audiology, which includes one to two hours of lectures and none to four hours of tutorials, depending on the faculty concerned. The amount of audiometric training at nursing schools varies from none to five hours and that of lectures in otolaryngology from three to twenty hours. Better co-ordination between departments of otolaryngology, general practice and paediatrics is needed when arranging teaching in paediatric audiology for medical students. Trainee child welfare nurses seem to need more guided practice in audiometry, and there is an obvious need for increasing the amount of practice in audiological departments. Specialist clinics should plan and implement a programme for updating training in paediatric audiology, including evaluation of the programme.