Abstract

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B

OHDAN

G

WORYS1

, H

ENRYK

K

ORDECKI2

, M

ARIA

K

NAPIK

−K

ORDECKA3

,

A

NDRZEJ

K

ARMOWSKI4

Maternal Age and Neonatal Development

Wiek matki a rozwój noworodka

1_{Department of Normal Anatomy, Silesian Piasts University of Medicine in Wrocław, Poland} 2_{Institute of Computer Science, Device and the Robotics, Wrocław University of Technology, Poland} 3_{Department and Clinic of Angiology, Arterial Hypertension and Diabetology, Silesian Piasts University}

of Medicine in Wrocław, Poland

4_{First Department and Clinic of Gynecology and Obstetrics, Silesian Piasts University of Medicine in Wrocław,}

Poland

Adv Clin Exp Med 2008, 17, 6, 649–654 ISSN 1230−025X

Abstract

Material and Methods. A group of 732 male and 758 female newborns was analyzed. Only first−born neonates from singleton pregnancies born naturally and in very good condition (10 Apgar points) were included.

Results. Statistical analysis showed that the mother’s age during pregnancy had statistically significant influence on the newborn’s wellness.

Conclusions. Assuming that higher values of the metrical neonatal parameters indirectly indicate that their devel− opment is close to optimal, it can be said that newborns delivered by teenage mothers had the lowest wellness level. This conclusion was valid for all the parameters investigated and depended neither on the newborn’s sex nor preg− nancy duration. This rule was more evident for body length and weight and less for the circumference parameters (Adv Clin Exp Med 2008, 17, 6, 649–654).

Key words:maternal age, neonate development.

Streszczenie

Materiał i metody. Analizie poddano 732 noworodki płci męskiej i 758 płci żeńskiej. Uwzględniono tylko nowo− rodki, które pochodziły z pierwszej ciąży jednopłodowej, urodzone siłami natury i co do których nie było żadnych zastrzeżeń lekarskich (10 punktów w skali Apgar). W ten sposób autorzy chcą wykluczyć z badań wpływ rytmiki porodów, który mógłby wypaczyć uzyskane rezultaty, a w następstwie prowadzić do fałszywych wniosków. Noworodki bez klinicznych oznak wcześniactwa lub przenoszenia kwalifikowano jako normalne, niezależnie od tego, ile dni trwała ciąża.

Wyniki. Wpływ wieku matki na zmienność cech metrycznych noworodka oceniano jednoczynnikową analizą wariancji, wykorzystując pakiet programów komputerowych Statistica Pl.

Wnioski. Przeprowadzona analiza statystyczna upoważnia do stwierdzenia, że wiek matki w czasie ciąży i poro− du wywiera znaczący (istotny statystycznie) wpływ na dobrostan nowo narodzonego dziecka. Jeżeli przyjmie się, że większe wartości cech metrycznych noworodka wskazują pośrednio na to, że jego rozwój jest bardziej zbliżony do rozwoju optymalnego, to należy stwierdzić, że najmniejszym dobrostanem cieszą się dzieci zrodzone z matek, które nie przekroczyły 20. roku życia. Taki wniosek nasuwa się po analizie wszystkich badanych cech, niezależnie od płci dziecka oraz długości trwania ciąży. Jest to bardziej widoczne w wartościach długości i masy ciała noworodka, słabiej w wartościach obwodu głowy. Zależność najmniej dotyczy wartości obwodu klatki piersiowej (Adv Clin Exp Med 2008, 17, 6, 649–654).

Słowa kluczowe:wiek matki, rozwój noworodka.

Investigating neonatal body weight, Piasecki [1] found that the mother’s age was closely related to the order of delivery. Partitioning according to the mother’s age and delivery order, the author

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take into account the delivery order when investi− gating the influence of the mother’s age and the results are therefore entirely different. Abdul Karim and Beydoun [2], Miller [3], and Bożiłow et al. [4] discovered no relationship between maternal age and the size of the fetus and newborn. However, Piasecki [1], Cieślik and Waszak [5], and Orkwiszewska and Gładykowska−Rze−czycka [6] discovered a statistically significant influence of this factor. The present authors believe that the dif− ferences in these results were mainly caused by not taking into account the regularity (“rhythmici− ty”) of deliveries. Studies on small numbers of newborns force the inclusion of first−born as well as next−born neonates. It is evident that a 20−year− old mother cannot deliver six or seven newborns. The mother of six newborns would be at least 30. The aim of this paper was to evaluate newborn wellness according to their physical development in relationship to their mothers’ age at the time of delivery. It was assumed that wellness, determined by maximal comfort during prenatal development, allows the optimal use of genetic potential and paragenetic features in this period. As a result, the values of the investigated newborn parameters increase. Obviously, the higher the parameter val− ues the better the wellness.

Material and Methods

Newborns born naturally at Silesian Piast University of Medicine, Wrocław, in the period of 1989–2001 were investigated. The newborn group consisted of 732 males and 758 females. Only first−borns from singleton pregnancies born natu− rally and in very good condition (10 Apgar points) were included. In this way the influence of deliv− ery rhythmicity on the results was eliminated. Newborns who were not premature or who were beyond term were also included in the group regardless of pregnancy duration. For each new− born, body length, body weight, head circumfer− ence, and chest circumference were measured.

To eliminate the influence of newborn age, the group of newborns was divided into four sub− groups. The three first percentiles were chosen as the subgroup boundaries. In this way four sub− groups were obtained, with pregnancy periods of < 272, 272–280, 281–288, and > 288 days. Maternal age was analyzed in six groups, i.e. < 20, 20–23, 24–27, 28–31, 32–35, and > 35 years old. Each newborn had his/her own information card with the values of the analyzed parameters as well as all available clinical data related to the newborn and the mother.

First the Kolmogorow−Smirnow test was used to check if all the data samples were chosen from

random variables with a normal distribution. In all cases the results were positive. The influence of maternal age on the variability of the neonatal parameters was checked using one−way ANOVA. The differences between the average values of the newborns’ parameters were tested for the different maternal age groups. In this way statistically sig− nificant differences were discovered and marked. All calculations were made with a significance level of α= 0.05.

Results

The basic statistical parameters and the results of variance analysis are shown in Tables 1–4. Neonatal body length was closely related to the mother’s age. Newborns with the smallest body length were delivered by mothers younger than 20. The physical development of these mothers was not yet completed. Newborns delivered by the old− est mothers were a little longer, but the difference was not statistically significant. Newborns deliv− ered by 20− to 27−year−old mothers had the longest body lengths. Variance analysis showed statistical− ly significant differences compared with other newborns. This tendency did not depend on the duration of pregnancy or the newborn’s sex.

Neonatal body weight had the same variabili− ty as body length. The weights of newborns of young mothers were less than those of older moth− ers. The differences were statistically significant. The differences in neonatal weight for mothers over 20 years old were not statistically significant. This rule was the same for males and females and did not depend on the duration of pregnancy.

The variability in head circumference in the newborns was very similar to that in neonatal body mass. Newborns delivered by teenage mothers had smaller head circumferences those delivered by mothers over 20 years old. This rule was valid for both males and females. However, smaller differ− ences were observed than those for neonatal length and weight. Statistically significant differences appeared only in newborns with a proper duration of pregnancy. This tendency was also observed in newborns from pregnancies of improper duration, but the differences in this case were not statistical− ly significant. The differences were greater for males than for females.

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Discussion

The results of the statistical analysis showed that the mother’s age during pregnancy had a sta− tistically significant influence on the newborn’s wellness. Assuming that higher values of the met− rical neonatal parameters indirectly indicate that their development is close to optimal, one can say that newborns delivered by teenage mothers had the lowest wellness level. This was valid for all the parameters investigated and depended neither on the newborn’s sex nor pregnancy duration. This rule was more evident for body length and weight and less for the circumference parameters.

There is no simple explanation for the influ− ence of the mother’s age. It seems that Thomp−

son’s suggestion [7] that “physiological uterus capacity” changes depending on pregnancy time should be taken into account. The longer the preg− nancy time, the greater the uterine plasticity and flexibility. Abdul−Karim and Beydoun [2] stated that in the last trimester, when development is faster and the fetus’ linear dimensions are consid− erably increasing, the uterus is not able to follow this progress. In this period the comfort of the inter−uterine environment decreases and wellness is much lower. As a consequence, a lowering of perinatal fetal growth appears. This process is much more profound in teenage mothers in whom the developmental process is not yet finished and therefore newborns delivered by mothers younger significantly different are in bold

Tabela 1.Zróżnicowanie długości ciała noworodków z uwzględnieniem ich wieku, płci oraz wieku matki w chwili porodu. Wartości zaznaczone czcionką pogrubioną są istotne statystyczne na poziomie α= 0,05

Males Mother’s age Females

(Chłopcy) (Wiek matki) (Dziewczynki)

N mean SD range age N mean SD range age

10 503 26.3 421–591 < 271 < 20 13 507 24.2 430–602 < 271

32 521 22.5 432–587 20–23 31 531 25.3 421–589

29 523 24.1 385–599 24–27 26 528 26.4 458–652

18 513 26.7 421–579 28–31 22 509 25.9 439–677

12 514 25.11 462–612 32–35 14 512 23.9 429–578

11 509 23.17 483–592 < 35 10 511 25.7 471–579

29 514 25.1 485–633 272–280 < 20 31 517 26.7 429–645 272–280

58 543 21.8 458–673 20–23 72 554 25.8 4–3–658

66 537 22.1 471–658 24–27 66 553 27.3 473–599

28 523 25.8 399–587 28–31 41 531 26.3 418–703

21 521 27.5 432–605 32–35 30 526 25.9 467–607

22 517 26.2 493–669 < 35 23 526 24.7 431–634

31 516 24.9 461–599 281–288 < 20 27 519 27.2 407–579 281–288

69 545 21.6 469–703 20–23 69 551 25.3 453–673

61 541 23.1 487–689 24–27 65 554 24.8 466–639

34 536 22.8 483–742 28–31 32 549 26.0 419–680

25 531 24.6 457–688 32–35 28 532 25.1 432–679

21 519 26.2 462–657 < 35 19 522 27.4 466–688

17 514 25.9 472–645 > 289 < 20 16 521 26.4 483–672 > 289

46 545 24.5 488–638 20–23 42 547 25.7 468–688

41 541 23.8 442–678 24–27 37 543 27.9 461–632

27 537 24.6 462–598 28–31 19 531 26.4 387–622

18 526 26.2 468–689 32–35 14 519 27.4 451–627

16 519 28.3 465–677 < 35 11 521 24.9 439–672

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than 20 have smaller body dimensions than those delivered by older mothers. Uterine flexibility is, in this case, a global notion; it combines genetic, physiological (taking into account hormonal and mother−fetus transport factors), and anatomical factors (placenta mass, villous surface, and umbil− ical cord length) [8].

Interpreting the present results one can say that mothers 20–30 years old are in the optimal age for delivering well−developed children. For mothers over 30 years old, a lowering of neonatal wellness was discovered, probably caused by the beginnings of development stagnation. This leads to almost invisible anatomic−physical changes which, following the authors cited above, can be described as “physiological uterus capacity”.

The authors concluded that the mother’s age during pregnancy and delivery has a significant influence on the newborn’s wellness. Newborns delivered by teenage mothers have the lowest well− ness level. The lower wellness level causes decreased body weight and length. The head and chest circumferences are less affected by the low wellness level. The optimal maternal age for deliv− ering a well−developed newborn is 20–27 years. Teenage mothers in whom the development process is not completed deliver newborns with smaller body dimensions than older mothers. For mothers over 30 years old, decreased wellness in the perina− tal period was discovered. This is caused by the beginnings of the development stagnation.

Table 2.Variability of neonatal body weight according to the newborn’s and mother’s ages at delivery. Values which are significantly different are in bold

Tabela 2.Zróżnicowanie masy ciała noworodków z uwzględnieniem ich wieku, płci oraz wieku matki w chwili porodu. Wartości zaznaczone czcionką pogrubioną są istotne statystyczne na poz. α= 0,05

10 2900 449 1800–4520 < 271 < 20 13 2850 530 1320–4330 < 271

32 3202 432 1250–4310 20–23 31 3250 472 1820–4580

29 3221 504 1680–5030 24–27 26 3104 431 2030–4900

18 3180 502 2010–4590 28–31 22 3220 429 2000–5270

12 3289 471 1920–5100 32–35 14 3245 398 2190–5600

11 3209 399 1450–4300 < 35 10 3261 453 1570–5880

29 3129 429 2000–5400 272–280 < 20 31 3020 489 2000–5640 272–280

58 3430 409 2100–5620 20–23 72 3483 453 2100–5720

66 3388 387 2300–6720 24–27 66 3457 473 1980–6020

28 3202 471 2240–5840 28–31 41 3348 407 2310–5880

21 3287 433 2370–5990 32–35 30 3276 533 2100–5670

22 3292 494 2100–5670 < 35 23 3342 489 2210–5540

31 3199 502 2100–5320 281–288 < 20 27 3043 327 2000–5490 281–288

69 3453 471 2320–6000 20–23 69 3387 386 2310–5720

61 3388 442 2120–5430 24–27 65 3468 346 2100–5990

34 3326 462 2220–5780 28–31 32 3351 428 1840–5730

25 3402 419 2450–5470 32–35 28 3388 501 1990–5690

21 3377 439 2100–6020 < 35 19 3421 469 2010–5470

17 3284 488 2210–5890 > 289 < 20 16 3189 455 2200–5790 > 289

46 3507 513 2320–5600 20–23 42 3476 503 2320–5800

41 3542 471 2210–5460 24–27 37 3482 484 2310–5650

27 3488 434 2190–5820 28–31 19 3469 433 1790–6010

18 3505 451 2390–5440 32–35 14 3590 389 2000–5890

16 3592 473 2190–5880 < 35 11 3621 402 2100–6100

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References

[1] Piasecki E:Charakterystyka populacyjna ciężaru ciała noworodków polskich. MiPA 1988, 109, 159–196. [2] Abdul−Karim RW, Beydoun SN: Growth of the human fetus. Clin Obstet Gynecol 1974, 17, 37–52.

[3] Miller JE:Determinants of intrauterine growth retardation: evidence against maternal depletion. J Biosoc Sci 1989, 21, 235–243.

[4] Bożiłow W, Sawicki K, Poradnik E, Kurlej W, Gworys B:Zmienność masy ciała podczas rozwoju prenatalnego i okołoporodowego. Przegl Antrop 1992, 55, 1–2, 45–55.

[5] Cieślik K, Waszak M:Z badań nad wpływem czynników pozagenetycznych na rozwój płodu oraz ich udziału w przyczynach urodzeń martwych. Przegl Antrop 1988, 54, 151–158.

[6] Orkwiszewska A, Gładykowska−Rzeczycka J: Częstość urodzeń i stan rozwoju noworodków przedwcześnie urodzonych z wagą ciała poniżej 2500 g w rejonie Gdańska. Przegl Antrop 1994, 57, 33–37.

[7] Thompson AM, Billewicz WZ, Hytten FE:The assessment of fetal growth. J Obstet Gynaecol Br Cmwlth 1968, 75, 903–916.

[8] Gworys B, Kordecki H:The neonate wellness dependency on the level of mother−fetus transport development. In press. Pol J Environmental Stud 2008.

are significantly different are in bold

Tabela 3.Zróżnicowanie obwodu głowy noworodków z uwzględnieniem ich wieku, płci oraz wieku matki w chwili porodu. Wartości zaznaczone czcionką pogrubioną są istotne statystyczne na poziomie α= 0,05

10 321 19.2 234–489 < 271 < 20 13 318 18.7 210–521 < 271

32 329 18.7 219–467 20–23 31 327 18.6 231–489

29 327 18.6 254–509 24–27 26 329 21.2 233–523

18 329 16.9 318–541 28–31 22 326 18.8 213–459

12 326 17.9 252–478 32–35 14 327 19.4 241–529

11 329 18.1 234–469 < 35 10 329 20.1 233–478

29 322 21.3 217–511 272–280 < 20 31 324 22.1 239–533 272–280

58 334 18.7 287–465 20–23 72 338 19.8 221–430

66 332 19.3 231–509 24–27 66 336 18.6 294–523

28 333 18.2 246–576 28–31 41 341 19.5 258–511

21 337 19.7 211–41 32–35 30 334 19.2 238–479

22 335 20.2 238–479 < 35 23 335 20.3 237–543

31 324 20.4 216–499 281–288 < 20 27 329 21.8 219–499 281–288

69 343 18.9 251–532 20–23 69 342 18.5 232–476

61 347 17.8 264–479 24–27 65 339 17.8 241–569

34 345 17.9 232–513 28–31 32 343 19.3 214–478

25 339 19.3 241–469 32–35 28 348 18.6 241–553

21 343 17.5 228–518 < 35 19 347 20.4 238–463

17 326 21.1 217–499 > 289 < 20 16 328 22.0 229–562 > 289

46 337 19.2 238–470 20–23 42 339 20.1 267–510

41 337 19.6 215–543 24–27 37 338 18.9 251–499

27 341 17.8 237–531 28–31 19 352 18.9 237–531

18 339 18.2 251–488 32–35 14 343 17.3 231–469

16 335 17.9 216–469 < 35 11 337 19.9 263–405

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Address for correspondence:

Bohdan Gworys

Department of Normal Anatomy Silesian Piasts University of Medicine Chałubińskiego 6a

50−368 Wrocław Poland

Tel.: +48 71 784 13 42 E−mail: [email protected]

Conflict of interest: None declared

Received: 7.10.2008 Revised: 10.11.2008 Accepted: 21.11.200

Table 4.Variability of neonatal chest circumference according to the newborn’s and mother’s ages at delivery. No statisti− cally significant differences were discovered

Tabela 4.Zróżnicowanie obwodu klatki piersiowej noworodków z uwzględnieniem ich wieku, płci oraz wieku matki w chwili porodu. Nie stwierdzono istotnych statystycznie różnic

10 317 14.3 212–501 < 271 < 20 13 314 23.8 245–487 < 271

32 319 15.6 234–478 20–23 31 317 24.9 221–488

29 321 24.9 231–478 24–27 26 318 15.3 233–495

18 318 27.8 212–503 28–31 22 321 25.3 225–506

12 321 21.0 217–462 32–35 14 318 21.2 211–489

11 318 17.6 243–468 < 35 10 319 20.2 241–467

29 328 21.8 232–498 272–280 < 20 31 331 19.8 229–502 272–280

58 329 17.8 241–506 20–23 72 331 17.2 232–488

66 327 16.3 241–482 24–27 66 328 18.3 241–499

28 329 17.8 226–477 28–31 41 326 15.3 219–488

21 332 18.2 225–495 32–35 30 337 16.9 229–469

22 328 14.8 231–512 < 35 23 329 16.2 251–479

31 331 20.2 269–492 281–288 < 20 27 328 19.0 278–416 281–288

69 335 16.7 245–511 20–23 69 331 18.4 264–463

61 334 16.3 235–521 24–27 65 334 18.6 253–503

34 334 18.9 230–465 28–31 32 329 19.2 239–465

25 335 20.3 246–521 32–35 28 331 18.6 222–498

21 336 20.3 228–459 < 35 19 329 19.3 251–507

17 332 16.9 212–476 > 289 < 20 16 328 17.6 231–462 > 289

46 336 17.3 243–439 20–23 42 328 16.9 251–478

41 334 15.7 261–520 24–27 37 332 12.9 230–460

27 337 16.1 216–492 28–31 19 336 17.9 228–476

18 334 14.8 225–471 32–35 14 337 16.3 219–483

16 337 18.3 231–494 < 35 11 334 19.9 248–506