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358 British Journal of Midwifery June 2010 Vol 18, No 6
CLINICAL PRACTICE
Effect of age on maternaland fetal outcomes
Within the UK maternal age at the birth
of the first child is steadily increasing
(Nwandison and Bewley, 2006; Lewis,
2007; Office for National Statistics, 2008). Women
who defer childbearing in this way do so for many
reasons. A womans decision regarding the right
time to embark upon a pregnancy may vary with
personal, family, cultural and religious beliefs.However, once a woman over 35 years of age has
made a decision to proceed with a pregnancy she
faces a grim reality.
Andersen et al (2000) noted that approximately
20% of all wanted pregnancies in 35-year-old women
will result in fetal loss (defined as stillbirths, spon-
taneous abortions, ectopic pregnancies) rising to
54.5% at 42 years of age. A woman aged 3539 years
has a risk of spontaneous abortion of 24.6%, rising
to 51% at 4044 years and 93.4% at 45 years or
more (Andersen, 2000). This means that a woman
attending antenatal clinic may previously have had
several wanted pregnancies ending in loss. That
woman may have come from a peer group within
her fertility clinic or social network where friends
have failed to achieve a pregnancy at all. Once
attending for antenatal care, expectations are high
but older women face the unpleasant prospect of
being advised of a poorer obstetric outcome than
their younger counterparts, with no realistic strat-
egies available to improve outcome. This requires
careful counselling, as anxiety itself is associated
with worse pregnancy outcomes (Alder, 2007;
Glynn et al, 2008; Wisborg, 2008).
When searching for an evidence base from
which to counsel such women the literature should
be interpreted with the following points in mind:
Any study in this group of women will only
include a small number of older mothers
(1020% >35 years; 24% >40 years (Gilbert,
1999; Jolly, 2000; Cleary-Goldman, 2005; Reddy
et al, 2006; Hoffman, 2007) and 0.005% >50
years (Donoso, 2008)
The control groups used for comparison
(e.g. 2029, 3039, 4049, >40 years of age)vary widely and older mothers often have chil-
dren with older fathers, which very few studies
correct for (Astolfi, 2004)
Primiparity, plurality and the use of assisted
reproductive technologies all increase with the
age of the population studied and independ-
ently affect the outcomes observed.
By virtue of their advanced age women have
had more time to accumulate co-morbidities. They
are more likely to have experienced surgery, had
car accidents, suffered infectious diseases, gained
weight and smoked for longer. The prevalence
of medical conditions such as hypertension anddiabetes all increase with age. These population
changes are mirrored in the ageing pregnant popu-
lation. Salihu et al (2003) noted more maternal
complications including chronic hypertension and
diabetes in women >35 years. To correct for these
co-morbidites in research may be unrealistic in
that few women of advanced age will be disease
free, but for those who are, correction allows a
more accurate estimation of risk.
Maternal and fetal outcomes
In their prospective study of 36 056 singleton
pregnancies Cleary-Goldman et al (2005) showed
that placenta praevia (adjusted odds ratio (AOR)
2.8), placental abruption (AOR 2.3) caesarean
section (CS) (AOR 2.0) and perinatal mortality
(AOR 2.2) were all increased in older mothers
when the effects of race, parity, body mass index,
education, marital status, smoking, pre-existing
medical conditions, previous adverse obstetric
outcome and use of assisted reproductive tech-
nologies (ART) were controlled for. The authors,
however, showed no statistically significant asso-
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AbstractA womans decision regarding the right time to embark upon a
pregnancy may vary with personal, family, cultural and religiousbeliefs. However once a woman over 35 years of age has made adecision to proceed with a pregnancy she faces an increased risk ofadverse pregnancy outcome, particularly in those with co-morbidities,multiple pregnancies and/or those conceived through ovum donation.
These women need support and carefully planned obstetric care.Women seeking assisted reproductive technologies at over 35 yearsof age should be offered pre-pregnancy counselling and be advised of
the benefit of single embryo transfer. Society as a whole, midwives,obstetricians and gynaecologists, should advocate for policies thatenable women to reproduce safely without personal cost to theireducation, careers, identity and their own or their offsprings health.
Anna P Kenyon
Clinical Lecturer/sub-
specialty trainee in
maternal and fetal
medicine, Institute
for Womens Health,
University College
London
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35British Journal of Midwifery June 2010 Vol 18, No 6
CLINICAL PRACTIC
ciation between age 35 years or older and other
outcomes e.g. threatened abortion, pre-eclampsia
(PET), gestational hypertension, pre-term labour
and operative vaginal delivery. Interestingly, this
study did not show advancing age to be asso-
ciated with hypertensive complications despite
confirming that chronic hypertension was morecommon among older women. The authors suggest
this is as a result of controlling for covariates asso-
ciated with gestational hypertension and PET
e.g. history of medical conditions and use of ART
(Cleary-Goldman, 2005).
Hoffman (2007) looked only at singleton preg-
nancies in a multiethnic population and compared
women 3539 years (13 902) and 40 or more years
old (3953) with those less than 35 years. Hoffman
noted that after correcting for race, parity, chronic
hypertension, PET, diabetes, gestational diabetes
and gestational age at delivery the risk of having an
infant of low birthweight was increased:
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360 British Journal of Midwifery June 2010 Vol 18, No 6
CLINICAL PRACTICE
(OR 2.22, 95%; CI: 1.33.77) (Simchen et al, 2009).
In a study by Porreco (2005) PET was signifi-
cantly more prevalent among patients conceiving
with ovum donation (OR 2.67, 1.046.82), even
though 22% of the control group developed PET.
One of 11 women (9%) over 45 years conceiving
spontaneously developed PET compared to 20/39(51%) conceiving with ART and donor eggs (P
0.016) (Porreco, 2005). Henne (2007) reported an
increase in pre-term labour, PET and protracted
labour in women conceiving after ovum donation
correcting for parity.
StillbirthRisk of stillbirth may increase with advanced
maternal age. In the general population, still-births affect 1 in 200 pregnancies (Smith and
Fretts, 2007). The additional risk that advanced
Table 1: Studies reporting risks of stillbirth with maternal age
Ref Stillbirthdefinition
Risk Studypopulation
PopulationAge inyears (n)
ComparatorAge inyears
3540years
>40 years >45years
>50 years
Donoso(2008)
Fetal death OR(95% CI)
2 817 959 >50 (217) 2034 3.7(1.210.5)
Hoffman(2008)*
Fetal death AOR(95% CI)
126 402 >40 (3 953) 40(45 982 612singletons)
1.44**(1.381.5)
Jacobsson(2004)
Intrauterinefetal death>28 weeks
AOR(95% CI)
1 566 313 4044(31 662) >45(1,205)
2029 2.1 (1.82.4)for 4044years
3.8(2.26.4)
Salihu(2003)
Loss >20weeks
AOR(95% CI)
12 066 854 4049(3 982 062 )
2029 1.94 (1.672.26)singletons 4049 years
2.20(1.014.75)
singletons>50 (539) 0.72 (0.431.2)
multiples at 4049years
1.6(0.43.00)multiples
Gilbert(1999)
Infant death AOR(95% CI)
1 160 000 >40 (24 032) 2029 1.2 (0.8-1.8)nulliparous1.5 (1.3-1.8)multiparous
Jolly(2000)
Stillbirth OR(95% CI)
385 120 >40 (7331)3540(41 327)
1834 1.41(1.171.70)
1.83(1.292.61)
Reddy et
al (2006)
Stillbirth RR
(95% CI)
5 458 735 35-39
(545,873)>40(109,174)
40(130 857)
2034 1.28(1.241.32)
1.72(1.631.81)
* adjusted for ethnic group, parity, hypertension, pre-eclampsia, gestational diabetes** adjusted for race/parityAOR: adjusted odds ratioOR: odds ratio
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36British Journal of Midwifery June 2010 Vol 18, No 6
CLINICAL PRACTIC
maternal age poses has been investigated in
several studies (Table 1) and appears to increase
in a continuum with rising age (Andersen, 2000;
Bateman, 2006). The largest increase in risk for
women 35 years or older may start at 39 weeks
gestation and peak at 41 weeks. Extremes of
gestation are associated with the highest weeklyrisk of stillbirth (>41 weeks and 2023 weeks) and
women at 40 years or older appear to have the
largest risk (Reddy et al, 2006). The risk appears
to persist even when confounding variables are
taken into consideration. For example, in the
study by Reddy et al (2006) the effect of maternal
age persisted despite accounting for medical
disease, parity, race and ethnicity.
Fretts and Duru (2008) have suggested that the
risk of stillbirth in women >40 years of age may be
as high as 1 in 116 pregnancies at >37 weeks. This
increased risk is still observed when corrections are
made for coexisting medical conditions, which notonly are more common in women of advanced age
but also are independently associated with stillbirth
(PET, gestational diabetes mellitus, multiple preg-
nancies) (Fretts et al, 1995; Fretts, 2005; Hoffman,
2007). Fretts et al (1995) report that even when
recognized coexisting conditions that contribute to
fetal death are controlled for, women over 35 years
of age have a risk of fetal death twice as high as that
among their younger counterpart.
Causes of the increased risk remain unclear,
however, placental abruption and umbilical cord
complications all appear to rise with increasing
age (Bateman, 2006). Cleary-Goldman (2005)suggested that for singletons greater than 40
weeks gestation the risk of abruption is an
odds ratio of 2.3. Other important maternal
risk factors for stillbirth such as nulliparity
and obesity are also seen to rise in women of
advanced maternal age (Nwandison and Bewley,
2006; Lewis, 2007; Smith and Fretts, 2007; Off ice
for National Statistics, 2008). However, the
most significant contribution to the increased
risk of stillbirth in woman of advanced age is
the increased risk of unexplained fetal death
(OR 2.2, 1.33.8) (Bateman, 2006).
It should be noted that older mothers have bene-
fitted from the reduction in stillbirth in general
populations that we have seen over time, and this
is confirmed by Fretts et al (1995). Between the
years 19601993 stillbirth rates declined overall
and in women aged 35 years or older, the rate of
stillbirths per 1000 births decreased from 16.5
in 1960 to 5.8 in 19901993. The absolute risk of
stillbirth has been greatly reduced, however, the
higher relative risk for older women persists and
exactly what clinicians should do to reduce this is
not clear (Stein and Susser, 2000).
Older age, whether because of the co-morbidi-
ties that accompany it, the plurality that is observed,
or the effect of age alone, does appear to be asso-
ciated with adverse outcome. Prospective mothers
presenting pre-conception or in early pregnancy
(following referral as a result of age identified onrisk factor screening) may wish to know the risk
associated with their pregnancy (Gilbert, 1999),
and in the context of that increased risk what
interventions are available to them to improve
outcome. However, few studies have addressed
interventions in older mothers.
In considering stillbirth, Hannah et al (1992)
have shown that in any pregnancy of more than
41 weeks gestation induction of labour results in
lower rates of caesarean section than serial ante-
natal monitoring with similar rates of perinatal
morbidity and mortality. Given that women of
40 years or older have a similar stillbirth risk at39 weeks to 2529-year-olds at 41 weeks (Andersen,
2000) perhaps interventions should therefore be
offered earlier in these women.
However, a word of caution: women of advance
age may not labour as efficiently as their younger
counterparts. A Dublin group employing active
management of labour in all nulliparous women
attending their unit in spontaneous labour under-
took an analysis of outcome with respect to age.
The need for oxytocin, the incidence of prolonged
labour, instrumental delivery, intrapartum caesarean
section and intrapartum caesarean section because
of dystocia all increased with increasing maternalage (Treacy, 2006). The observed differences were
not accounted for by differences in birthweight,
epidural use or gestational age.
Heffner et al (2003) reported risks for caesarean
section by induction status, gestational age and
maternal age stratified for parity in singleton
pregnancies over 36 weeks. Maternal age greater
than 35 years was associated with an increased
caesarean section rate among nulliparous women
and maternal age over 40 years was associated with
an increased risk in multiparous women (Heffner
et al, 2003). Similar increased caesarean section
rates were reported by Gilbert et al (Gilbert, 1999);
47% caesareasn setion in nulliparous women 40
years old or more compared to 22.5% in those aged
2029 years. However the authors acknowledge
that a diagnosis of dystocia is physician-derived
and that they were unable to conclude what anxiety
maternal age brought to clinical decision making on
the part of the parturient and the doctor (Gilbert,
1999). This suggests that intervention might reduce
the risk of stillbirth, but may increase caesarean
section and maternal morbidity rates.
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362 British Journal of Midwifery June 2010 Vol 18, No 6
CLINICAL PRACTICE
ConclusionsThe risks of adverse pregnancy outcome appear
to increase with advancing maternal age, particu-
larly in those with multiple pregnancies conceived
with ovum donation. Women seeking ART over
35 years of age should be offered a full and frank
discussion and be advised of the benefit of singleembryo transfer. Society as a whole, midwives,
obstetricians and gynaecologists should advocate
for policies that enable women to reproduce safely
without personal cost to their education, careers,
identity and their own or offsprings health. BJM
Acknowledgement The author would like to thank Dr Susan Bewley without
whose inspiration and assistance this would not have
been possible and Dr M Nwandison in her contribution to
the original article. This topic is covered in greater depth
in: Kehoe S, Bewley S, Ledger W, Nikolaou D, eds (2009)
Reproductive ageing in older mothers. 56th RCOG Study
Group, London
Alder J, Fink N, Bitzer J, Hosli I, Holzgreve W (2007)
Depression and anxiety during pregnancy: A risk factor
for obstetric, fetal and neonatal outcome? A critical
review of the literature.J Matern Fetal Neonatal Med
20(3): 189209
Andersen AMN (2000) Maternal age and fetal loss: popu-
lation based register Linkage study. Br Med J. 320(7251):
170812
Astolfi P (2004) Late paternity and stillbirth risk. Hum
Reprod19(11): 2497501
Bateman BT (2006) Higher rate of stillbirth at the extremes
of reproductive age: A large nationwide sample of deliv-
eries in the United States.Am J Obstet Gynecol194(3):
8405Cleary-Goldman J C Fc (2005) Impact of maternal age on
obstetric outcome. Obstet Gynecol105(5): 98390
Donoso E (2008) Maternal, perinatal and infant outcome
of spontaneous pregnancy in the sixth decade of life.
Maturitas59(4): 3816
Fretts RC (2005) Etiology and prevention of stillbirth.Am J
Obstet Gynecol193(6): 192335
Fretts RC, Duru UA (2008) New indications for antepartum
testing: Making the case for antepartum surveillance
or timed delivery for women of advanced maternal age.
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MB (1995) Increased maternal age and the risk of fetal
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Glynn LM, Schetter CD, Hobel CJ, Sandman CA (2008)
Pattern of perceived stress and anxiety in pregnancy
predicts preterm birth. Health Psychology Jan;27(1): 43-51
Hannah ME, Hannah WJ, Hellmann J, Hewson S, Milner
R, Willan A (1992) Induction Of Labor As Compared
With Serial Antenatal Monitoring In Postterm
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Jolly M (2000) The risks associated with pregnancy in
women aged 35 years or older. Hum Reprod15(11): 24337
Luke B (2007) Contemporary risks of maternal morbidity
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Lewis GE (2007) Saving mothers lives: Reviewing maternal
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Confidential Enquiry into Maternal and Child Health
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(accessed 20 May 2010)
Porreco RP (2005) Expectation of pregnancy outcome
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Reddy UM, Ko CW, Willinger M (2006) Maternal age
and the risk of stillbirth throughout pregnancy in the
United States.Am J Obstet Gynecol195(3): 76470
Salihu HM (2003) Childbearing beyond maternal age 50
and fetal outcomes in the United States. Obstet Gynecol
102(5): 100614Simchen MJ, Shulman A, Wiser A, Zilberberg E, Schiff E
(2009) The aged uterus: multifetal pregnancy outcome
after ovum donation in older women. Hum Reprod
24(10): 25003
Smith GCS, Fretts RC (2007) Stillbirth. Lancet370: 171525
Stein Z, Susser M (2000) The risks of having children in
later life. Br Med J320(7251): 16812
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Key pointsIt is impossible (and wrong) for others to determine when it is the righttime for a woman, or couple, to have a baby. Women who defer child-bearing do so for many reasons, both within and outside their control.Care, support and respect of these and all women should be the healthprofessionals first concern.The risks of adverse pregnancy outcome appear to increase withadvancing maternal age.Women seeking assisted reproductive technology and/or ovum dona-tion over 35 years of age should receive pre-pregnancy counselling andbe advised of the benefit of single embryo transfer.The available data suggest that in terms of physiology, age 2035 yearsremains the best age for childbearing.
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