| Changes in MaternalAge and the Incidence of Down Syndrome |
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Chang Weon Oh1, Sung Su Lim1, Ki Bok Kim1, Won Jin Kee2 |
1Department of Pediatrics, Kwangju Christian Hospital, Kwangju, Korea
2Department of Cytogenetics Laboratory, Kwangju Christian Hospital, Kwangju, Korea |
| 산모 연령 및 Down증후군 발생빈도의 변화에 관한 고찰 |
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오창원1, 임성수1, 김기복1, 기원진2 |
1광주기독병원 소아과
2광주기독병원 세포유전학실 |
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| Abstract |
Purpose
: The incidence of Down syndrome, the most common chromosoaml anomaly, increases
with the advanced maternal age. Recently, however, the incidence of Down symdrome was
reported to have decreased with wide acceptance of prenatal diagnosis and planned parenthood,
prompting us to re-evaluate the incidence of Down syndrome in relation to changes in maternal
age.
Methods
: Subjected to study were 296 Down cases: 26 newborn Down's among the 58,479
deliveries undergone in our hospital (KCH) during the period over 2 decades from April 1974
through December 1994; and 270 cases, whose maternal age at delivery could be traced with
certainty, among 366 Down cases confirmed by genetic counseling. The observation period was
divided into three: Period I, before 1979 (n=66); Period II, from 1980 to 1989 (n=127); and
Period III, after 1990 (n=103).
Results
:
1) The change in maternal age at delivery
Of total 58,479 deliveries, 0.5% were born to mothers younger than 20 years, 21.3% were
aged 20-25 years; 57.7% (33,722) were aged 26-30 years; 16.9% fell between 30-35 years; and
3.6% were above 35 years. Deliveries of old mothers (>35 ys) were 4.9% in Period I, which
significantly decreased to 2.8% in Period II, increased again to 4.1% in Period III.
2) Changes in Down incidence among those delivered in KCH
Overall Down incidence among those delivered in KCH was 0.44/1000 (26/58,479); however,
it was 0.93/1000 in Period I, 0.16 in II, significantly lower; and 0.59/1000 in Period III. Of the
26 Downs born in KCH 18 were born to mothers younger than 35 years (0.03%), whereas 8
were born to mothers older than 35 years (0.8%). The Down incidence among mothers younger
than 35 years did not significantly differ among the periods, while for the mothers aged over 35
years it decreased from 1.0% (6/576) in Period I to 0% (0/825) in Period II, and back to 0.3%
(2/698) in Period III, indicating that Down incidence among old mothers significantly decreased
recently, compared with the early period.
3) Changes in maternal age and Down incidence among those confirmed by genetic
counseling.
Of those 270 Down cases, 226 were born to mothers younger than 35 years, whereas 44
were delivered by old mothers aged above 36 years. Old mothers had Down babies in 23.6%
(13/55) in Period I, but it significantly decreased to 11.5% (14/122) in Period II, but it
recovered to 18.2% (17/93) in Period III.
4) Relationship between karyotype pattern and maternal age
Of total 296 Down cases 260 (87.8%) had typical pattern of 21-trisomy, 32 (10.8%)
translocation, 4 (1.4%) mosaicism. Those with typical trisomy had mean age (¡¾S.D.) of 30.3
(¡¾6.0) year and those with mosaicism 30.8 (¡¾6.2) year, whereas those with translocation were
significantly younger with the mean age of 26.6 (¡¾2.5) year.
Conclusion
: During the last 2 decades, the deliveries by old mothers tended to decrease, and
also the overall incidence of Down syndrome has significantly decreased, especially among those
born to mothers older than 35 years. Recently, however, maternal age tends to increase for
various reasons, necessitating due emphasis on prenatal diagnosis. |
| Key Words:
Maternal Age, Incidence of Down Syndrome |
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