Quartely Digest
Volume 6 - Number 1 July 1996

Preface

Due to the fact that Vital Statistics Agency files are continually being updated, totals compiled by addition of the annual quarters will not correspond exactly to year-end figures. For the same reason, depending on the date the data are extracted, there will be differences in numbers presented in this year's Quarterly Digests and those eventually reported in the Vital Statistics 1996 Annual Report. Therefore, the numbers provided in this report should be considered provisional. Finally, the usual cautions regarding random fluctuations in values, particularly those involving small numbers, must be noted.

In 1981, women giving birth at age 35 and older accounted for 4.8% of live births. By 1995, this proportion of older mothers had increased to 14%. This issue's feature article "Increased Maternal Age and the Outcome of Pregnancy" uses national and provincial comparisons to demonstrate a nation-wide trend in delayed childbearing. This is followed by a British Columbia birth review, provincial and regional, examining whether increased risks of maternal and infant complications, low birth weight, preterm birth, cesarean delivery, stillbirth, etc. existed among women aged 35 and older. Wherever possible, changes such as additional cause of death categories, percentage, or year-to-date totals, have been added to the Quarterly Digest as requested by our readers. Suggestions for article topics or contributions are also welcome. Your support and input into this publication is greatly appreciated.

R.F Cronin Assistant Deputy Minister Corporate Services Ministry of Health and Ministry Responsible for Seniors

R.J. Danderfer Executive Director Vital Statistics Agency Ministry of Health and Ministry Responsible for Seniors

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British Columbia
Local Health Areas

British Columbia
Local Health Areas (LHA)
within Regional Health Boards (RHB)

There has been a rising trend in advanced maternal age, particularly at age 35 and older, reflected by increasing age specific fertility rates (35 - 39 years). This has raised public concerns regarding the outcomes of delayed pregnancy. Many studies have shown that pregnancy among older women is associated with risks of various maternal complications, cesarean birth, preterm birth, low birth weight birth, and others (Cunningham, F.G. and Leveno, K.J., 1995, Cnattingius, S., et al, 1992, Gordon, D., et al, 1991).

During the past decade, the proportion of women having their first birth at age 35 and older has increased in countries like Canada, the United States (Cunningham, F.G. and Leveno, K.J., 1995), Sweden (Cnattingius, S., et al, 1992), Spain (Melchor, J.C., et al , 1994), and others (Milkulandra, F, 1993). The growing trend is partially due to the large birth cohorts following World War II up to the mid-1960s, and is also due to the increasing trend of women entering the work force and delaying their childbearing for educational, professional, or personal reasons.

In British Columbia, the number of babies born to older mothers (35 - 39 years) has increased from 1,768 in 1981 to 5,645 in 1995. Over the same time period, the age specific fertility rate increased from 19.2 per 1,000 women aged 35 - 39 in 1981 to 34.2 in 1995. In addition, age specific rates for women aged 20 - 29 decreased from 104.8 in 1981 to 85.5 in 1995. This shift in numbers and fertility toward older mothers resulted in a nearly tripling of the proportion of 35+ year old mothers who accounted for 4.8% of live births in 1981 and 14.0% by 1995.

The objective of this study was to examine all births in British Columbia in an 8-year period and assess the influence of increased maternal age on both infants and mothers. As a population based study, this report begins with a brief presentation of national and provincial comparisons, which demonstrates a nation-wide trend in delayed childbearing. It is followed by a British Columbia birth review, in which statistical information on diverse pregnancy outcomes, birth trends and regional birth outcomes are presented. The effect of delayed childbearing on pregnancy outcomes was assessed by examining whether increased risks of maternal and infant complications, low birth weight birth, preterm birth, cesarean birth, stillbirth, etc. existed among women aged 35 and older.

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METHODOLOGY

This study was based on birth data obtained from the birth registry at the British Columbia Vital Statistics Agency, Ministry of Health and Ministry Responsible for Seniors. A total of 357,378 live births and 2,395 stillbirths were registered from 1987 to 1994. The primary source of data for this report were derived from the Physician's Notice of Birth (PNOB) which is submitted to the Agency within 48 hours of the birth event. Birth data such as maternal age, delivery mode, birth weight, gestational age, maternal complications, perinatal and congenital conditions, etc., were reviewed, extracted, and then classified into categories as listed below. The assessment of delayed childbearing was performed for maternal age groups 30 to 34 and 35+. For comparison, the maternal age group 20 to 29 was considered as the normal or reference group. Female population estimates (P.E.O.P.L.E. 19) prepared by BC STATS, Ministry of Finance and Corporate Relations, were used for the calculation of age specific fertility rate.

Selected maternal and infant complications were analyzed. The following conditions were considered to have potentially serious health impact on mothers or infants from the point of view of frequency of occurence and/or medical seriousness.

I.  Maternal Complications:

• Antepartum haemorrhage (6400- 6419)
• Hypertension/Eclampsias (6420 - 6429)
• Diabetes mellitus and gestational diabetes (6480, 6488)
• Multiple gestation (6510 - 6519)
• Malposition and malpresentation of fetus, disproportion and obstructed labour
• (6520 - 6539, 6600 - 6609)
• Abnormality of reproductive organs ( 6540 - 6549)
• Fetal abnormality affecting mother (6550 - 6569)
• Abnormality of forces of labour and prolonged labour (6610 - 6619, 6620 - 6621)
• Complications of umbilical cord (6630 - 6639)
• Obstetrical trauma (6640 - 6659)
• Postpartum haemorrhage (6660 - 6663)

II. Perinatal Complications:


• Slow fetal growth, SGA, and fetal malnutrition (7640 - 7649)
• Birth trauma (7670 - 7679)
• Intrauterine hypoxia and birth asphyxia (7680 - 7689)
• Respiratory conditions of fetus and new-born (769, 7700 - 7709)
• Isoimmunization disorders and perinatal jaundice (7730 - 7747)

III. Congenital Anomalies


• Congenital anomalies of brain, nervous system and spinal cord (7400 - 7429)
• Congenital anomalies of ear, face and neck ( 7440 - 7449)
• Congenital anomalies of heart (7450 - 7469)
• Congenital anomalies of respiratory system (7480 - 7489)
• Musculoskeletal anomalies (7540 - 7569)
• Chromosomal anomalies (7580 - 7589)
• All anomalies (7400 -7599)

To examine the effect of advancing maternal age on the outcomes of pregnancy, the rates of low birth weight (<2500 g), preterm (<37 weeks), cesarean section, small for gestational age, and selected complications and anomalies were assessed. Rates for various outcomes were calculated for primiparous women and multiparous women respectively and presented as percentages of total births to specific parity group and maternal age group. The national and provincial review was presented based on 1982 - 1992 Statistics Canada annual birth data.

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HIGHLIGHTS and COMMENTS

Nationally, in 1982, mothers aged 35 and older accounted for 4.9% of all live births. By 1992 this proportion had increased to 9.9%, doubling in only 10 years. In this same period, British Columbia's increase in the pro-portion of older mothers was even greater (2.4 times), and increased from 4.8% to 11.7%. In 1982, British Columbia ranked fifth in the nation behind the Northwest Territories (5.6%), Ontario (5.5%), Prince Edward Island (5.5%) and Quebec (5.0%). By 1992, BC had the second highest proportion of elderly gravidae and was only slightly lower than the Yukon (13.6%).

National age specific fertility rates for women age 35 to 39 increased from 20.2 (per 1,000 women) in 1982 to 28.9 in 1992. The corresponding rates for BC were 21.5 and 31.4, an approximate 46% increase. This BC rate was sixth highest in the nation in 1982 and ranked fourth highest in 1992.

Between 1987 and 1994, there were 357,378 infants live born to BC residents. 11.0% of these infants had mothers who were aged 35 or older and 2.7% had age 35+ first-time mothers. The annual percentage of live births to elderly mothers increased from 8.7% in 1987 to 13.4% in 1994 while the age (35-44) specific fertility rate rose from 1.6 to 2.1 (per 100 women).

Over the eight year period, 4.8% of mothers age 20-29, 4.9% of mothers age 30-34, and 5.5% of mothers 35+ had low birth weight (LBW) babies. By 1994 the rates were 4.9%, 5.2%, and 6.1% respectively. The proportion (7.2%) of premature infants born to older mothers was also higher than for the "ideal" (age 20-29) group (5.8%).

The annual provincial cesarean section rate declined from 21.1 (per 100 live births) in 1987 to 19.8 in 1994. Over the eight year period, the C-section rate was 27.1 for women age 35+ compared to 19.9 for women age 20-29. This higher rate for older mothers was even more remarkable among mothers delivering their first live born (19.9% vs. 34.9%) indicating that higher cesarean rates at age 35+ is more than a function of repeat cesareans.

Delayed childbearing was also associated with increased risk of other maternal and infant complications such as antepartum haemorrhage, hypertension/eclampsias, diabetes, multiple gestation, fetal malposition/ malpresentation, disproportion and obstructed labour, maternal abnormality of reproductive organs, abnormal and prolonged labour, fetal growth retardation, infant hypoxia, and respiratory system and chromosomal congenital anomalies.

The impact of "baby boom" women who are delaying childbearing can be seen in the ever increasing trend in births to women aged 35 and older. Regardless of their parity, when compared to women age 20-29, women age 35+ were at greater risk for most of the maternal complications and perinatal conditions considered in this study as well as for stillbirth. Also, there is increased risk of cesarean section, low birth weight, and preterm birth among primiparous women aged 35 and older. A modest elevation in the risk of cesarean section among elderly multiparas may reflect a higher rate of repeat cesarean among this group.

Higher proportions of mothers aged 35 and older were found in urban areas such as West Vancouver, North Vancouver, Vancouver, Greater Victoria etc. while regional variations in rates of low birth weight, preterm birth, cesarean, and selected complications in older mothers indicated higher fre-quencies among rural regions (based on residence of mother). This may be related to the type, level, utilization, and accessibility of perinatal care programs in rural areas.

Older mothers-to-be are more likely than their younger counterparts to present with gestational diabetes, fetal distress, hypertension, abnormal forces of labour etc. and therefore require more frequent assisted delivery. This study also examined the frequency of elective (no reason provided) cesarean and found higher rates among elderly primigravidae.

Increasing numbers of elderly gravidae and parallel increases in the pregnancy, labour, and delivery problems associated with this group as noted in this report, will continue to require adaptations by obstetrical care providers. This may equate to more frequent prenatal visits, increased diagnostics, more thorough monitoring and to prenatal education that focuses on the older mother in order to reduce or manage these problems.

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REFERENCES

Barkan, S.E., and Barcken, M.B. (1987). Delayed childbearing: No evidence for increased risk of low birth weight and preterm delivery, American Journal of Epidemiology, Vol. 125, No. 1.

Baskett, T.F. (1977). Grand multiparity - a continuing threat: a 6-year review, Journal of the Canadian Medical Association, Vol. 116.

Berkowitz, G.S., Skovron, L., Lapinski, R.H., and Berkowitz, R.L. (1990). Delayed childbearing and the outcome of pregnancy, The New England Journal of Medicine, Vol. 322, No. 10.

Bobrowski, R.A., and Bottoms, S.F. (1994). Underappreciated risks of the elderly multipara, American Journal of Obstetrics and Gynecology, Vol. 172, No. 6.

Breslow, N. E., and Day, N.E. (1990). Statistical Methods in Cancer Research Volume 1 - The Analysis of Case - Control Studies, Lyon: IARC Scientific Publications.

Buehler, J.W., Kaunitz, A.M., Hogue, C.J.R., Hughes, J.M., Smith, J.C., and Rochat, R.W. (1986). Maternal Mortality in Women Aged 35 Years or Older: United States, Journal of the American Medical Association, Vol. 255, No. 1.

Cnattingius, S., Forman, M.R., Berendes, H.W., Graubard, B.I., and Isotalo, L. (1992) Effect of age, parity, and smoking on pregnancy outcome: A population-based study, American Journal of Obstetrics and Gynecology, Vol. 168, No.1, Part 1.

Cnattingius, S., Forman, M. R., Berendes, H. W., and Isotalo, L. (1992). Delayed childbearing and risk of adverse perinatal outcome, Journal of the American Medical Association, Vol. 268, No. 7.

Cunningham, F.G. and Leveno, K.J. (1995). Childbearing Among Older Women - The Message is Cautiously Optimistic, The New England Journal of Medicine, Vol. 333, No. 15.

Edge, V., and Lario, R.K. (1992). Pregnancy Outcome in Nulliparous Women Aged 35 or Older, American Journal of Obstetrics and Gynecology, Vol. 168, No. 6 Part 1.

Forman, M.R., Meirik, O., and Berendes, H.W. (1984). Delayed childbearing in Sweden, Journal of the American Medical Association, Vol. 252, No. 22.

Frette, R.C., Schmittdiel, J., McLean, F.H., Usher, R.H., and Goldman, M.B. (1995). Increased maternal age and the risk of fetal death, The New England Journal of Medicine, Vol. 333, No. 15.

Gordon, D, Milbery, J., Daling, J., and Hickok, D. (1991). Advanced maternal age as a risk factor for cesarean delivery, Obstetrics and Gynecology, Vol. 77, No. 4.

Kirz, D. S., Dorchester, W., and Freeman, R. K. (1984). Advance maternal age: The Mature Gravida, American Journal of Obstetrics and Gynecology, Vol. 152, No. 1.

Melchor, J.C., Rodriguez-Alarcon, J., Fernandez-Llebrz, L., Benito, J.A., Linares, A., and Aranguren, G. (1994). Delayed Childbearing and Pregnancy Outcome, Zentralbl Gynakol, 116.

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Glossary

APGAR:
A scoring method of evaluation done at one minute and five minutes after the complete birth of an infant (disregarding the cord and placenta). Each of five objective signs are evaluated and given a score of 0, 1 or 2. A total score of 10 indicates an infant in the best possible condition. The signs evaluated are; heart rate, respiratory effort, muscle tone, response to stimuli (generally catheter in nostril), colour. The score taken at one minute is an index of asphyxia and of the need for assisted ventilation; the five minute score is a more accurate index of likelihood of death or neurologic residual.

Assignment of Health Region(HR):
Cases are assigned to HR by the aggregation of appropriate LHAs.

Assignment of Local Health Area (LHA):
Allocation of LHA, in the case of births and deaths is based upon the usual residence (by postal code) of the mother and deceased respectively. Marriages are assigned to LHAs according to the place of event. Standard Geographical Code (SGC) is used in the absence of postal code.

Birth Order:
Denotes the number position of the present birth relative to previous live births. That is, whether the live birth being counted is the 1st, 2nd, 3rd, etc. live born infant to a particular mother.

Elderly Gravida:
Any mother who was 35 years of age or older at the time of delivery of a live born infant.

External Causes of Death:
Deaths due to environmental events, circumstances and conditions as the cause of injury, poisoning, and other adverse effects. Broad categories include accidents, suicide, medical or abnormal reactions, homicide, legal intervention, misadventures and injury from war operations. Standard tables under this heading include deaths due to accidents, suicide, homicide and other. Accidents are subdivided by the following categories:

• motor vehicle accidents (MVA) (ICD E810-E825, E929.0),
• poisoning (E850-869, E929.2),
• falls (E880-E888, E929.3),
• burns/fire (E890-899, E924, E929.4),
• drowning (E830, E832, E910),
• other accidents - all codes from E800-E949 not already noted.
• Suicide ICD-9 codes are E950-E959;
• homicide (E960-969);
• "other" consists of legal intervention (E970-978), undetermined if accidental or purposely inflicted (E980-989) and war operations (E990-999).

• rheumatic/valvular: 391-398, 424
• hypertension: 401-405
• ischemic: 410-414, 429.2
• conductive & dysrythmic: 426-427
• heart failure: 428
• congenital: 745-746
• other: pulmonary - 415-417, inflammatory - 420-423, 429.0, cardiomyopathy - 425, 429.3, degenerative - 429.1, other, ill-defined or unspecified - 429.4-429.9

Infant Deaths:
Deaths of children under one year of age.

Low Birth Weight:
Any liveborn infant weighing less than 2500 grams.

Multipara:
(Para II, III, IV etc.), a woman who has had two or more pregnancies which resulted in viable children. Multiple Gestation: a twin, triplet, quadruplet, etc. pregnancy.

Neoplasms (ICD-9 140-239):
Although the vast majority of deaths in this category are due to malignant cancer, also included are benign, in-situ, and unspecified "tumours". Detailed ICD-9 breakdown used in "Neoplasm Deaths" tables are;

• lung: includes trachea, bronchus, lung (ICD-162) and pleura (163)
• female breast: (ICD-174)
• colorectal: includes colon (ICD-153) and rectum, rectosigmoid junction and anus (154) other G.I. (Gastrointestinal): includes esophagus (ICD-150), stomach (151), small intestine and duodenum (152), liver & intrahepatic bile ducts (155), gallbladder and extra-hepatic ducts (156), pancreas (157), peritoneum (158), other and ill-defined within digestive organs (159).
• female reproductive: includes uterus (ICD-179), cervix (180, 182), placenta (181), ovary and adnexa (183), vagina & external genitalia (184).
• male reproductive: includes prostate (ICD-185), testis (186), penis & other genitalia (187).
• blood lymph: includes lymphatic and haematopoietic tissue (200-208).
• other malignancy: includes malignant neoplasms of other (e.g. lip, oral cavity, pharynx, nose, ear, larynx, heart, bone and connective tissue, urinary tract, eye, brain, endocrine glands), ill-defined or unspecified sites (140- 149, 160, 161, 164, 165, 170-173, 175, 188-189, 190-199).
• non-malignant & unspecified: includes benign (210-229), in-situ (230-234), and neoplasms of unspecified nature (e.g. "tumor" - 239).

• respiratory disease with four sub-categories of emphysema (ICD-492), chronic obstructive pulmonary disease (COPD) (496), pneumonia/influenza (480-487), and other respiratory diseases (ICD-460-478, 490-491, 493-495, 500-519).
  
• diabetes (250)
  
• alcohol related - see above.
  
• AIDS: includes AIDS and HIV infections (ICD-042-044).
  
• cerebro and other vascular: includes cerebrovascular disease (ICD-430-438), disease of arteries and veins (440-456), hypotension (458), and other circulatory system disease (459).
  
• liver disease: ICD-570-573.

Primipara:
(Para I), a woman who has had one pregnancy which resulted in a viable child.

Small for Gestational Age (SGA):
A term applied to an infant whose weight at birth is inappropriately low relative to its gestational age. SGA determination is based on Lubchenko's growth charts (Lubchenco & Hansman, USA, 1963).

Stillbirth:
The complete expulsion or extraction from its mother after at least 20 weeks of pregnancy or after attaining a weight of at least 500 grams, of a product of conception in which, after expulsion or extraction, there is no breathing, beating of the heart, pulsation of the umbilical cord or unmistakable movement of voluntary muscle.

Teenage Mother:
Any mother who was age 19 or less at the time of delivery.

Total Fertility Rate (TFR):
The rate is calculated by summing all of the age specific birth rates multiplied by the number of years by which the age specific rates are grouped. " The total fertility rate indicates the number of live births that a group of 1,000 women would have if they experienced, during their childbearing years (age 15 to 44), the age specific birth rates observed in a given calendar year. It is a hypothetical measure that shows the implications of current levels of fertility by age for completed family size." (National Centre for Health Statistics. Supplements to the monthly vital statistics reports: advance reports, 1987. National Centre for Health Statistics . Vital Health Stat. 24 (4) p.5. 1990)

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Correction:

LHA		Count
24	Kamloops	2
33	Chilliwack	1
39	Vancouver	1
41	Burnaby	1
46	Sechelt	1
52	Prince Rupert	1
57	Prince George	1
67	Ladysmith	1
69	Qualicum	1
70	Alberni	2
71	Campbell River	1
88	Terrace	1

Contributors' Note:

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Readers' Note:

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