A number of environmental factors that involve gestation or birth have been associated with the development of type 1 diabetes in the child in various studies, reviewed in (Larsson et al. 2004). How exactly these factors influence the development of type 1 diabetes is not known. The following factors have been found to increase the risk of type 1 diabetes:

Subsequent studies that have pooled data from various studies have supported some of these findings. High birth weight, for example. An analysis of the data from 29 studies found that babies weighing over 7.7 lbs (3.5 kg) at birth have a 6% higher risk of type 1 diabetes, and those that weigh over 8.8 lbs (4 kg) at birth have a 10% higher risk of developing the disease. This study controlled for factors such as maternal diabetes, gestational age, and some other factors that might affect birthweight (Cardwell et al. 2010b). An analysis of pooled data on maternal preeclampsia, however, found little evidence of increased risk of type 1 diabetes (Henry et al. 2011).

Neonatal jaundice has also been associated with a small increased risk of type 1 diabetes (McNamee et al. 2011).

 

An analysis of the data from 30 studies found that on average, there is a 5% increased risk of type 1 diabetes for every 5 year increase in maternal age. That is, children of older mothers have a slightly increased risk of developing type 1 diabetes. Children of older fathers, on the other hand, do not appear to have an increased risk of type 1 diabetes. The authors argue that increasing maternal age can only explain a very small percentage ("hardly any") of the increasing incidence of type 1 diabetes in children. Why might a higher maternal age increase the risk of type 1? We do not know. The chromosomal changes that are more common in children of older mothers are not thought to be involved in the development of type 1diabetes. It is possible that accumulated exposure to environmental contaminants could play a role (Cardwell et al. 2010a). Older people do have higher levels of some contaminants, such as persistent organic pollutants (Patterson et al. 2009).

 

Birth order has not been consistently associated with type 1 diabetes (Stene et al. 2004). That is, first born vs. later born children do not appear to have a higher or lower risk of disease. However, a newer meta-analysis of 31 separate studies found there was some evidence for a slightly lower risk of type 1 diabetes in later born children as compared to first born children, especially in children under 5 years of age. The association varied a lot between studies (Cardwell et al. 2010c). 

I was happy to learn that weight gain during pregnancy is not associated with the development of beta cell autoimmunity in the offspring (I gained a lot of weight while pregnant). The mother's BMI (body mass index) before pregnancy was not associated with beta cell autoimmunity in the offspring either (Arkkola et al. 2010). However, if the mother has diabetes, their children have an increased rate of BMI growth in late childhood (ages 10-13), thus increasing their long term risk for obesity (Crume et al. 2011a). Another study by the same authors found that gestational diabetes in the mother was associated with later weight gain in the offspring at ages 6-13 (Crume et al. 2011b).  And, they also found that breastfeeding in infancy reduced the subsequent risk of this later weight gain. The authors suggest that adequate breastfeeding protects against childhood weight gain, and reduces the excess weight gain associated with exposure to diabetes in utero (Crume et al. 2011c).

Another study using pooled data found that there was a slightly reduced risk of type 1 diabetes in children spaced less than 3 years apart, as compared to those spaced more than 3 years apart (Cardwell et al. 2012).

Interestingly, an analysis of data from 20 studies found that Caesarean sections were associated with a 20% increased risk of type 1 diabetes in offspring. Why? The authors suggest that perhaps this association is due to the gut microbiota. The gut microbiota differ in children born by C-section compared with those born vaginally (Cardwell et al. 2008) (see the diet and the gut page for more on the gut and type 1 diabetes).

One study has also found differences in the levels of immune system cells called cytokines in babies born vaginally as compared to those born by C-section. Vaginal birth may instigate a form of inflammation that activates the baby's (and mother's) immune systems in a beneficial manner (Malamitsi-Puchner et al. 2005) (see the inflammation page for more on cytokines and inflammation).

A prospective U.S. study found that complicated deliveries (e.g., breech, forceps, vacuum extraction) was associated with increased risk of type 1 diabetes-related autoantibodies in children genetically at risk for type 1 diabetes. How complicated deliveries would influence the development of autoantibodies is not known. Unlike the above studies (which measured the development of type 1 diabetes), this study did not find that C-sections increased the risk of type 1-associated autoantibodies. The results of this study remained the same when women with gestational or type 1 diabetes were excluded from the analysis (Stene et al. 2004).

A number of additional factors may influence the development of type 1 diabetes during gestation or in early life. For information on breastfeeding and type 1 diabetes, see the breastfeeding page. The nutrition and wheat and dairy pages contain information on type 1 diabetes and early infant feeding or maternal diet during pregnancy. The viruses page discusses congenital rubella. The height and weight page considers growth in early life and type 1 diabetes. Vitamin D deficiency has been associated with pre-eclampsia (Mulligan et al. 2009), as well as type 1 diabetes.  

 

And, exposure to environmental contaminants is another important environmental factor to consider during gestation and early life, since many contaminants can cross the placenta. Contaminants that are toxic to the developing immune system are addressed on the autoimmunity page.

 

Pregnancy itself can lead to gestational diabetes in the mother; for more on gestational diabetes, see the types of diabetes page.

A number of environmental influences that occur during gestation and birth may be involved in the development of type 1 diabetes, although further studies would need to confirm these associations. How these factors affect disease development is also worthy of further consideration. The increasing use of C-sections may be a concern.