New indications for antepartum testing: making the case for antepartum surveillance or timed delivery for women of advanced maternal age

A prospective cohort study providing insights for markers of adverse pregnancy outcome in older mothers

Background

Advanced maternal age (≥35 years) is associated with increased rates of adverse pregnancy outcome. Better understanding of underlying pathophysiological processes may improve identification of older mothers who are at greatest risk. This study aimed to investigate changes in oxidative stress and inflammation in older women and identify clinical and biochemical predictors of adverse pregnancy outcome in older women.

Methods

The Manchester Advanced Maternal Age Study (MAMAS) was a multicentre, observational, prospective cohort study of 528 mothers. Participants were divided into three age groups for comparison 20–30 years (n = 154), 35–39 years (n = 222) and ≥ 40 years (n = 152). Demographic and medical data were collected along with maternal blood samples at 28 and 36 weeks’ gestation. Multivariable analysis was conducted to identify variables associated with adverse outcome, defined as one or more of: small for gestational age (< 10th centile), FGR (<5th centile), stillbirth, NICU admission, preterm birth < 37 weeks’ gestation or Apgar score < 7 at 5 min. Biomarkers of inflammation, oxidative stress and placental dysfunction were quantified in maternal serum. Univariate and multivariable logistic regression was used to identify associations with adverse fetal outcome.

Results

Maternal smoking was associated with adverse outcome irrespective of maternal age (Adjusted Odds Ratio (AOR) 4.22, 95% Confidence Interval (95%CI) 1.83, 9.75), whereas multiparity reduced the odds (AOR 0.54, 95% CI 0.33, 0.89). In uncomplicated pregnancies in older women, lower circulating anti-inflammatory IL-10, IL-RA and increased antioxidant capacity (TAC) were seen. In older mothers with adverse outcome, TAC and oxidative stress markers were increased and levels of maternal circulating placental hormones (hPL, PlGF and sFlt-1) were reduced (p < 0.05). However, these biomarkers only had modest predictive accuracy, with the largest area under the receiver operator characteristic (AUROC) of 0.74 for placental growth factor followed by TAC (AUROC = 0.69).

Conclusions

This study identified alterations in circulating inflammatory and oxidative stress markers in older women with adverse outcome providing preliminary evidence of mechanistic links. Further, larger studies are required to determine if these markers can be developed into a predictive model of an individual older woman’s risk of adverse pregnancy outcome, enabling a reduction in stillbirth rates whilst minimising unnecessary intervention.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12884-021-04178-6.

Pregnancy outcome in mothers over the age of 35

PURPOSE OF REVIEW

The proportion of pregnancies occurring in women of at least 35 years of age has increased from 6.2% in 1980 to 22.3% of births in 2016. This review summarizes recent epidemiological and basic scientific studies investigating the association between older maternal age and adverse pregnancy outcome(s), and clinical studies which investigate the effects of intervention to reduce adverse events.

RECENT FINDINGS

Women of at least 35 years of age have increased risk of maternal and foetal complications in pregnancy including: stillbirth, a small for gestational age baby, preterm birth, preeclampsia and maternal death. These risks increase with increasing age. The reasons for this increased risk are incompletely understood, but likely involve ageing of the maternal cardiovascular and endocrine systems which impacts upon placental function. Intervention, by induction of labour (IOL) at 39-week gestation does not increase operative deliveries or short-term adverse maternal and neonatal outcomes and would reduce perinatal mortality.

SUMMARY

The additional risks of pregnancy should be discussed with women of at least 35 years of age; additional foetal surveillance may be required in the antenatal period. The benefits and risks of IOL at 39-week gestation should be discussed with women at least 35 years of age.

Interventions to prevent stillbirth

Stillbirth is one of the most distressing complications of pregnancy and still occurs far too frequently. The rate of stillbirth has been decreasing worldwide but room for improvement remains even in high-income countries. Risk factors for stillbirth have been identified in an effort to detect those women at increased risk. However, risk factors are non-specific and do not identify most stillbirths. Strategies employed to screen the general population such as assessment of fetal activity, fetal growth screening and biomarkers have also been used to identify increased risk for stillbirth. As with clinical risk factors, these methods are non-specific. Interventions to prevent stillbirth include antenatal testing of high-risk women, ultrasonographic assessments of fetal growth and Doppler velocimetry as well as iatrogenic preterm or term delivery. Additional research into the role of these interventions and better identification of those at high risk for stillbirth will help to achieve further stillbirth reduction.

Gestational age-specific neonatal morbidity among pregnancies complicated by advanced maternal age: a population-based retrospective cohort study

OBJECTIVE

Compare significant neonatal morbidity frequency differences in advanced maternal age (AMA) versus non-AMA pregnancies, assessing which gestational week is associated with the lowest morbidity risk.

METHODS

Population-based retrospective cohort study. Adverse neonatal outcome frequency differences were stratified by each week of gestation. Multivariate logistic regression estimated the relative risk (RR) of composite neonatal morbidity for women aged 35-39, 40-44, 45-49 and 50-55 versus 18-34 years, adjusted sequentially for relevant risk factors.

RESULTS

Neonatal morbidity decreased with each advancing week of term gestation, lowest at 39 weeks for all the groups. Adverse neonatal outcome risk for births to AMA women increased at 40 weeks: 35-39 years adjRR 1.12 [1.01-1.24] and ≥40 years 1.24 [1.01-1.52]. Each older maternal age category had increased risk for overall neonatal morbidity: 35-39 years adjRR 1.11 [95% CI 1.08-1.15], 40-44 years 1.21 [95% CI 1.14-1.29] and 45-49 years 1.34 [95% CI 1.05-1.69].

CONCLUSIONS

Lowest neonatal morbidity risk is at 39-week gestation with a significantly increased risk observed thereafter, especially in women ≥40 years.

Risk factors for antepartum stillbirth and the influence of maternal age in New South Wales Australia: a population based study

Background

Maternal age is a known risk factor for stillbirth and delayed childbearing is a societal norm in developed country settings. The timing and reasons for age being a risk factor are less clear. This study aimed to document the gestational specific risk of maternal age throughout pregnancy and whether the underlying causes of stillbirth differ for older women.

Methods

Using linkage of state maternity and perinatal death data collections the authors assessed risk factors for antepartum stillbirth in New South Wales Australia for births between 2002 – 2006 (n = 327,690) using a Cox proportional hazards model. Gestational age specific risk was calculated for different maternal age groups. Deaths were classified according to the Perinatal Mortality Classifications of the Perinatal Society of Australia and New Zealand.

Results

Maternal age was a significant independent risk factor for antepartum stillbirth (35 – 39 years HR 1.4 95% CI 1.12 – 1.75; ≥ 40 years HR 2.41 95% CI 1.8 – 3.23). Other significant risk factors were smoking HR 1.82 (95% CI 1.56 –2.12) nulliparity HR 1.23 (95% CI 1.08 – 1.40), pre-existing hypertension HR 2.77 (95% CI 1.94 – 3.97) and pre-existing diabetes HR 2.65 (95% CI 1.63 – 4.32). For women aged 40 or over the risk of antepartum stillbirth beyond 40 weeks was 1 in 455 ongoing pregnancies compared with 1 in 1177 ongoing pregnancies for those under 40. This risk was increased in nulliparous women to 1 in 247 ongoing pregnancies. Unexplained stillbirths were the most common classification for all women, stillbirths classified as perinatal infection were more common in the women aged 40 or above.

Conclusions

Women aged 35 or older in a first pregnancy should be counselled regarding stillbirth risk at the end of pregnancy to assist with informed decision making regarding delivery. For women aged 40 or older in their first pregnancy it would be reasonable to offer induction of labour by 40 weeks gestation.

Prepregnancy risk factors for antepartum stillbirth in the United States

OBJECTIVE

To identify possible prepregnancy risk factors for antepartum stillbirth and to determine whether these factors identify women at higher risk for term stillbirth.

METHODS

This retrospective cohort study of prepregnancy risk factors compared 712 singleton antepartum stillbirths with 174,097 singleton live births at or after 23 weeks of gestation. The risk of term antepartum stillbirth then was assessed in a subset of 155,629 singleton pregnancies.

RESULTS

In adjusted multivariable analyses, African-American race, Hispanic ethnicity, maternal age 35 years or older, nulliparity, prepregnancy body mass index (BMI) 30 or higher, preexisting diabetes, chronic hypertension, smoking, and alcohol use were independently associated with stillbirth. Prior cesarean delivery and history of preterm birth were associated with increased stillbirth risk in multiparous women. The risk of a term stillbirth for women who were white, 25-29 years old, normal weight, multiparous, no chronic hypertension, and no preexisting diabetes was 0.8 per 1,000. Term stillbirth risk increased with the following conditions: preexisting diabetes (3.1 per 1,000), chronic hypertension (1.7 per 1,000), African-American race (1.8 per 1,000), maternal age 35 years or older (1.3 per 1,000), BMI 30 or higher (1 per 1,000), and nulliparity (0.9 per 1,000).

CONCLUSION

There are multiple independent risk factors for antepartum stillbirth. However, the value of individual risk factors of race, parity, advanced maternal age (35-39 years old), and BMI to predict term stillbirth is poor. Our results do not support routine antenatal surveillance for any of these risk factors when present in isolation.

LEVEL OF EVIDENCE

II.

Pregnancy in peri- and postmenopausal women: challenges in management

Pregnancy in peri- and postmenopausal women is associated with an increased risk of complications and represents several challenges in terms of clinical management. Women in these age groups typically fall into one of two distinct groups, those who have conceived following assisted reproductive techniques, using ovum donation and those who have conceived spontaneously. While both have age in common, they differ in terms of additional risk factors. Recipients of assisted reproductive technologies have pregnancy risks associated with that treatment, but are at lower risks of a fetus affected by aneuploidy. Furthermore, they have been rigorously screened for medical complications, but are more likely to be primiparous and have multiple pregnancies. In contrast, women conceiving spontaneously are more likely to be of high parity and have additional medical complications such as obesity, hypertension or diabetes. In addition to the increased risk of antenatal complications such as miscarriage, ectopic pregnancies, gestational diabetes and hypertension, these women have a high risk of unexplained stillbirth. They also have a very high rate of Caesarean section. All these risk factors interact to modify clinical management. However, there are no randomized trials available to guide clinical management, thus decisions must be made on a case-by-case basis.