Map of Simcoe Muskoka

Pregnancy and Before

Small & Large for Gestational Age Rate

Babies born small for their gestational age (SGA) weigh less than 90% of babies of the same gestational age and sex born in Canada (excluding Ontario) between 1994 and 1996. These reference weights were established during a period of increased availability of ultrasound confirmation of gestational age. Similarly, babies born large for their gestational age (LGA) weigh more than 90% of babies of the same gestational age and sex born in Canada (excluding Ontario) between 1994 and 1996.  Only singleton babies are included in SGA and LGA rates. The data on this page are from the Discharge Abstract Database(DAD) and represent hospital births only.

Small for Gestational Age

SGA babies can also be low birth weight which means they weigh less than 2,500 grams (or 5 lbs 8 oz) when born at full term. SGA babies are more likely to become ill and/or die than normal birth weight newborns. They can also be at an increased risk of type 2 diabetes and coronary heart disease later in life.

In industrialized countries, maternal cigarette smoking during pregnancy accounts for 30% to 40% of SGA births; "genetically related factors", such as history of SGA pregnancies, maternal race, short maternal stature and fetal sex, account for 20% to 30%; nutritional factors including pre-pregnancy weight, low weight gain and low caloric intake accounts for 10% to 15%; and the number of times the mother has given birth and her general state of health for 5% to 10%. SGA babies are more common among younger mothers aged 15 to 24 years.

Large for Gestational Age

LGA babies are at higher risk for birth complications, including shoulder dystocia, brachial plexus injury and Erb’s palsy. The mother is also at higher risk for postpartum hemorrhage. Maternal diabetes has been established as an important risk factor for LGA. In turn, a baby with a high birth weight may be at increased risk for type 2 diabetes and childhood overweight/obesity later in life. LGA babies are more common among older mothers aged 30 to 44 years.

In the late 1980s SGA babies were more common than LGA babies, but this trend began changing in the early 1990s.  The SGA rate decreased and the LGA rate increased steadily until the LGA rate surpassed the SGA rate in 1992 in Simcoe Muskoka.  These trends continued until 2000 at which point the rates levelled off. In 2016 in Simcoe Muskoka, 8.9% of live singleton babies were small for gestational age, and 11.3% of all singleton babies were large for gestational age.