MHLU - Health Status Resource

Birth Outcomes

Birth Outcomes

Key Findings: 

Birth Rates and Counts

The annual number of live births in Middlesex-London ranged between 4,534 and 4,927 from 2006 to 2017, for an average of approximately 4,700 babies per year. During each of these years, slightly more male babies were born than female babies (Fig. 12.1.1)

The annual number of live births among the rural population of Middlesex-London ranged between 511 and 572 (Fig. 12.1.2) from 2006 to 2017. On average, rural births made up 11.4% of live births in Middlesex-London each year.

The birth rates in Middlesex-London, Ontario and the Peer Group saw a gradual decline from 2006 to 2017. During this period, the birth rate in Middlesex-London was similar to Ontario but slightly higher than the Peer Group (Fig. 12.1.3).

In Middlesex-London, the birth rate was significantly higher in the rural population compared to the urban population in 2011 and 2016. In 2016, the birth rate for the rural population was 11.7 per 1,000 population compared to 9.6 per 1,000 population in the urban population (Fig. 12.1.4).

While the birth rates for both populations decreased from 2011 to 2016, the decrease was smaller in the rural population (-3.3%) compared to the urban population (-5.9%).

Interpretive notes:

The birth rate is the annual number of live births in a given population per 1,000 people. It is influenced by the age structure of the population.3 For example, a population with a high percentage of women of reproductive age (15 to 49 years) will generally have a higher birth rate; whereas, a population with an older age structure will generally have a lower birth rate.

Data related to birth counts and rates can be useful for planning purposes to local government bodies and organizations that provide education, healthcare and other social services to the community.


Sex ratio at birth

The sex ratio at birth for Middlesex-London varied between 101.9 and 112.0 from 2006 to 2017, for an average of 105.9 (Figure 12.1.5). In 2013, the sex ratio for Middlesex-London was significantly higher than Ontario. For all other years during this period, the annual sex ratio for Middlesex-London was not significantly different from Ontario or the Peer Group.

Interpretive notes:

Sex ratio at birth is the number of male births divided by the number of female births. Around the world, the natural sex ratio at birth is around 105; that is, there are approximately 105 males born for every 100 females.4 With time, the sex ratio of a population is expected to equalize since males are at a higher risk of dying as they grow up compared to females.4


Multiple births

There were 3.2 multiple births per 100 live births in Middlesex-London in 2017. The percent of multiple births remained relatively steady from 2006 to 2017 for Middlesex-London, Ontario and the Peer Group. The larger fluctuations seen with the Middlesex-London data are expected based on the relatively small numbers of multiple births (Fig. 12.1.6).

Interpretive notes:

A multiple birth occurs when a mother delivers two or more infants from the same pregnancy. It is associated with a higher risk of complications for both the mother and babies compared to a singleton birth.

Mothers carrying multiples are more likely to have gestational diabetes, hypertension, pre-eclampsia, miscarriages, and Caesarian sections (C-sections). Babies of multiple births are more likely to be born prematurely and to have below-normal birth weights.7

According to the Public Health Agency of Canada, women who have undergone fertility treatments are around 20 times more likely to have a multiple pregnancy than if they had become pregnant naturally.7


Preterm births

The rate of preterm births in Middlesex-London was 8.1 per 100 live births in 2017, a rate similar to Ontario. Between 2007 and 2017, rates over time were stable in Middlesex-London (Fig 12.1.7).

Preterm birth rates in Middlesex-London, Ontario and the Peer Group were highest for mothers age 45 to 49 and lowest for mothers age 25 to 29 between 2013 to 2017 (Fig. 12.1.8). The margin of error (95% confidence interval) is higher for some age groups—particularly among mothers age 45 to 49—due to the small number of women who gave birth in those age groups.

For Ontario, the preterm birth rate among mothers age 45 to 49 was significantly higher than other maternal age groups. For Middlesex-London, the differences across age groups are not statistically significant due to the small number of women in some of the age groups (i.e., 15 to 19, 40 to 44, 45 to 49) (Fig. 12.1.8).

Interpretive notes:

A normal pregnancy can range from 38 to 42 weeks. A preterm birth occurs when a baby is born before 37 weeks (or 259 days) of pregnancy have been completed.8 The earlier a baby is born, the higher the risk of death or disability for the baby.


Birth weight

The low birth weight rate in Middlesex-London was 5.9 per 100 live births in 2017; a rate significantly lower than Ontario. Between 2007 and 2017, rates in Middlesex-London were relatively stable and similar to the Peer Group (Fig. 12.1.9).

The low birth weight rate among the urban population of Middlesex-London was 6.0 per 100 live births in 2017, compared to 4.8 in the rural population (not shown). From 2007 to 2017, rates were higher in the urban population compared to the rural population; although the differences were generally not statistically significant.

The high birth weight rate in Middlesex-London was 1.6 per 100 live births in 2017. Between 2006 and 2017, the rates for Middlesex-London, Ontario and the Peer Group were similar and were steady over time (Fig. 12.1.10).

The high birth weight rate among the urban population of Middlesex-London was 1.6 per 100 live births in 2017, compared to 1.9 in the rural population (not shown). From 2011 to 2017, the high birth weight rate was higher in the rural population compared to the urban population, although the differences were not statistically significant.

Interpretive notes:

A baby’s weight at birth is an important indicator of newborn and maternal health.9

A low birth weight is defined as a birth weight of less than 2,500 grams (5.5 pounds), regardless of the gestational age of the baby.10 The most common causes of low birth weight are preterm birth (before 37 weeks of pregnancy have been completed) and restricted fetal growth.11

A high birth weight is defined as a birth weight of 4,500 grams (9.9 pounds) or more, regardless of the gestational age of the baby.12 Mothers carrying high-weight fetuses have a higher risk of Caesarian sections13, while babies with high birth weights have a higher risk of obesity later in life.14


Birth weight for gestational age

The rate of small for gestational (SGA) births in Middlesex-London was 8.4 per 100 live births in 2017. Compared to Ontario (9.7 per 100 live births), the rate in Middlesex-London was significantly lower (Fig. 12.1.11).

Rates of SGA births in Middlesex-London were relatively stable between 2006 and 2017, while those for Ontario increased slightly over time (Fig. 12.1.11).

The rate of SGA births among the urban population of Middlesex-London was 8.7 per 100 live births in 2017; a rate significantly higher compared to the rural population (5.5 per 100 live births). SGA birth rates were consistently higher among the urban population compared to the rural population from 2006 to 2017 (figure not shown).

The rate of large for gestational (LGA) births in Middlesex-London was 10.1 per 100 live births in 2017 (Fig. 12.1.12).

Rates of LGA births in Middlesex-London, Ontario and the Peer Group followed a similar pattern from 2006 to 2017. During this period, rates in Middlesex-London were not significantly different from Ontario or the Peer Group (Fig. 12.1.12).

LGA birth rates were consistently higher among the rural population of Middlesex-London compared to the urban population from 2006 to 2017; however, the differences were not statistically significant (figure not shown).

In Middlesex-London from 2013 to 2017, mothers age 15 to 19 had the highest small for gestational age (SGA) birth rates. SGA birth rates had an inverse relationship with maternal age; that is, the rates decreased as the mother’s age group increased (Fig. 12.1.13).

Similarly, mothers age 15 to 19 had the lowest large for gestational age (LGA) birth rates. LGA rates during this period increased with maternal age and were highest among mothers age 40 to 49 (Fig. 12.1.13).

Preterm birth rates were highest among mothers age 40 to 49, and lowest among mothers age 25 to 29 (Fig. 12.1.13).

Interpretive notes:

Birth weight for gestational age is a measure of fetal growth. It can be influenced by many different factors, including: ethnicity, socioeconomic status, gestational diabetes, maternal smoking, maternal height and weight, maternal weight gain during pregnancy, and the baby’s sex.15

While low birth weight is still an important measure of birth outcome, it is better to consider it within the context of the baby’s gestational age and sex.16 For example, a baby delivered at 37 weeks is likely to have a low birth weight compared to a baby born at 40 weeks, but may not be undersized compared to other babies of the same gestational age and sex.

A baby is considered small for gestational age (SGA) if the birth weight falls below the tenth percentile based on a sex-specific, population-based Canadian reference standard at 22 to 43 completed weeks.17

A baby is considered large for gestational age (LGA) if the birth weight is above the ninetieth percentile based on a sex-specific, population-based Canadian reference standard at 22 to 43 completed weeks.17


Stillbirths

The stillbirth rate in Middlesex-London was 15.2 per 1,000 births in 2017, compared to 8.9 in Ontario and 10.4 in the Peer Group. Between 2006 and 2017, stillbirth rates in Middlesex-London were significantly higher than Ontario each year except for 2014 and 2015. The larger fluctuations seen with the Middlesex-London data are expected based on the relatively small numbers of stillbirths (Fig. 12.1.14).

Interpretive notes:

A stillbirth (or fetal death) is the death of a fetus in the womb after 20 weeks of pregnancy. The stillbirth can happen during the pregnancy or delivery. Some stillbirths are linked to problems with the placenta and umbilical cord, birth defects or genetic problems with the baby, or health conditions in the mother; however, often the specific cause of a stillbirth cannot be determined.18

Advances in technology have greatly improved the ability to detect congenital anomalies during pregnancy.19 Increases in stillbirth rates have been associated with a rise in pregnancies being terminated due to serious birth defects.20


Ontario Public Health Standard: 

Healthy Growth and Development Guideline, 2018

Ontario Public Health Standards: Requirements for Programs, Services, and Accountability


References:

  1. Statistics Canada. Health Region (2014) Peer Groups – Working Paper [Internet]. Ottawa, ON: 2014 [cited 2018 Nov 9]. Available from: https://www150.statcan.gc.ca/n1/pub/82-402-x/2015002/wp-dt/wp-dt-eng.htm
  2. Cavazos-Rehg PA, Krauss MJ, Spitznagel EL, Bommarito K, Madden T, Olsen MA, et al. Maternal Age and Risk of Labor and Delivery Complications. Matern Child Health J [Internet]. 2015 [cited 2018 Nov 8];19(6):1202-11. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4418963/ DOI: 10.1007/s10995-014-1624-7
  3. Kent MM, Haub C. In (Cautious) Defense of the Crude Birth Rate. Popul Today. 1984;12(2):6-7.
  4. World Health Organization South-East Asia Regional Office. Sex Ratio [Internet]. 2018 [cited 2018 Nov 8]. Available from: http://www.searo.who.int/entity/health_situation_trends/data/chi/sex-ratio/en/#
  5. Statistics Canada. Sex of Person [Internet]. 2018 [cited 2018 Nov 9]. Available from: http://www23.statcan.gc.ca/imdb/p3Var.pl?Function=DEC&Id=24101
  6. Statistics Canada. Gender of Person [Internet]. 2018 [cited 2018 Nov 9]. Available from: http://www23.statcan.gc.ca/imdb/p3Var.pl?Function=DECI&Id=463349
  7. Public Health Agency of Canada. Health Risks of Fertility Treatments [Internet]. 2013 [cited 2018 Nov 8]. Available from: https://www.canada.ca/en/public-health/services/fertility/health-risks-fertility-treatments.html
  8. Public Health Agency of Canada. Canadian Perinatal Health Report, 2008 Edition [Internet]. Ottawa, ON: 2008 [cited 2018 Nov 8]. Available from: http://www.phac-aspc.gc.ca/publicat/2008/cphr-rspc/pdf/cphr-rspc08-eng.pdf
  9. United Nations Children’s Fund. Low Birthweight [Internet]. 2014 [cited 2018 Nov 8]. Available from: https://data.unicef.org/topic/nutrition/low-birthweight/
  10. World Health Organization. Global Nutrition Targets 2025: Low Birth Weight Policy Brief [Internet]. Geneva: 2014 [cited 2018 Nov 8]. Report No.: WHO/NMH/NHD/14.5. Available from: https://www.who.int/nutrition/publications/globaltargets2025_policybrief_lbw/en/
  11. United Nations Children’s Fund. Low Birthweight: Country, Regional and Global Estimates [Internet]. New York: UNICEF, 2004 [cited 2018 Nov 8]. Available from: https://www.unicef.org/publications/files/low_birthweight_from_EY.pdf
  12. Statistics Canada. Table 13-10-0064-01 Birth-Related Indicators (Low and High Birth Weight, Small and Large for Gestational Age, Pre-Term Births), by Sex, Five-Year Period, Canada and Inuit Regions [Internet]. 2018 [cited 2018 Nov 8]. Available from: https://www150.statcan.gc.ca/t1/tbl1/en/tv.action?pid=1310006401.
  13. Chatfield J. Acog Issues Guidelines on Fetal Macrosomia. American College of Obstetricians and Gynecologists. Am Fam Physician [Internet]. 2001 [cited 2018 Nov 8];64(1):169-70. Available from: https://www.aafp.org/afp/2001/0701/p169.html
  14. Parsons TJ, Power C, Logan S, Summerbell CD. Childhood Predictors of Adult Obesity: A Systematic Review. Int J Obes Relat Metab Disord [Internet]. 1999 [cited 2018 Nov 8];23 Suppl 8:S1-107. Available from: https://www.nature.com/articles/0801139.pdf?origin=ppub
  15. Storms MR, Van Howe RS. Birthweight by Gestational Age and Sex at a Rural Referral Center. J Perinatol [Internet]. 2004;24:236. Available from: http://dx.doi.org/10.1038/sj.jp.7211065 DOI: 10.1038/sj.jp.7211065
  16. Callaghan WM, Dietz PM. Differences in Birth Weight for Gestational Age Distributions According to the Measures Used to Assign Gestational Age. Am J Epidemiol [Internet]. 2010;171(7):826-36. Available from: https://academic.oup.com/aje/article/171/7/826/86578 DOI: 10.1093/aje/kwp468
  17. Kramer MS, Platt RW, Wen SW, Joseph KS, Allen A, Abrahamowicz M, et al. A New and Improved Population-Based Canadian Reference for Birth Weight for Gestational Age. Pediatrics [Internet]. 2001;108(2):e35. Available from: http://pediatrics.aappublications.org/content/pediatrics/108/2/e35.full.pdf DOI: 10.1542/peds.108.2.e35
  18. Centers for Disease Control and Prevention. Facts About Stillbirth [Internet]. 2017 [cited 2018 Nov 8]. Available from: https://www.cdc.gov/ncbddd/stillbirth/facts.html
  19. Van den Veyver IB. Recent Advances in Prenatal Genetic Screening and Testing. F1000Res [Internet]. 2016;5:2591. Available from: https://www.ncbi.nlm.nih.gov/pmc/PMC5089140/ DOI: 10.12688/f1000research.9215.1
  20. Joseph KS, Kinniburgh B, Hutcheon JA, Mehrabadi A, Basso M, Davies C, et al. Determinants of Increases in Stillbirth Rates from 2000 to 2010. CMAJ [Internet]. 2013 [cited 2018 Nov 9];185(8):E345-51. Available from: https://www.ncbi.nlm.nih.gov/pubmed/23569166 DOI: 10.1503/cmaj.121372

Last modified on: November 12, 2018

Jargon Explained

Birth rate
The annual number of live births per 1,000 population.

Peer groups
The grouping of Ontario public health units with socio-economic characteristics similar to those of Middlesex-London. It is based on the 2015 Statistics Canada Peer Group A that includes health regions from across Canada that are characterized by having population centres with high population density and a rural mix.1

Sex ratio at birth
The ratio of males born alive per 100 females born alive.

Sex of person
Refers to the sex assigned at birth based on a person’s reproductive system and other physical characteristics.5 A person’s sex may differ from a person’s gender; a person’s gender may change over time and reflects the gender that a person internally feels and/or the gender a person publicly expresses.6

Multiple live birth rate
The number of multiple live births per 100 live births.

Preterm birth rate
Number of live births delivered before 37 completed weeks of gestation per 100 live births.

Low birth weight rate
The number of live births with a birth weight of less than 2,500 grams, per 100 live births.

High birth weight rate
The number of live births with a birth weight of 4,500 grams or more, per 100 live births.

Small-for-gestational-age rate
The number of live births with a birth weight below the tenth percentile of birth weights for their gestational age and sex, per 100 live births.

Large-for-gestational-age rate
The number of live births with a birth weight above the ninetieth percentile of birth weights for their gestational age and sex, per 100 live births.

Stillbirth rate
The number of births that are stillborn per 1,000 births (live or still).