Lifestyle, nutrient intake, iron status, and pregnancy outcome in pregnant women of advanced maternal age

Korean society is aging rapidly at an unprecedented pace and is expected to become an aged society (where people who are 65 years or older will account for more than 14 percent of the total population) by 2018 and a super aged society (where people who are 65 years or older will account for more than 20 percent of the total population) by 2026. The birth rate in 2008 was found to be 1.19, which remains at the world's lowest level. Also, the age of pregnant women has increased, in which the average age of women giving birth to, their first child is 30.82, which is 0.23 years greater than in 2007 [1].

There are various definitions of elderly gravida but it is commonly defined as a woman who has a baby when she is over age 35. The number of elderly gravidas is not only growing in Korea, but it is also a global trend caused by late marriage, remarriage, higher education level, women's advancement in society, and a delay in childbearing by economic factors. In Korea, the rate of elderly gravida increased from 2.0% in 1991 to 6.1% in 1994 to 13% in 2007 [1].

Hinz (USA) reported that the rate of natural childbirth declined when a mother's age was over 40 [2], and Khoshnood (France) observed that at 40-44 years old, female fertility dropped two-fold compared to women's who were 20-24 years old [3]. And there are many overseas reports that the maternal age is a crucial risk factor when predicting pregnancy outcomes [4-9]. However, Kale (Turkey) reported that there were no negative effects for a 45 year-old woman to deliver a large fetus [10].

Research on late childbearing in Korea showed undesirable results in-terms of pregnancy, such as obstetric prognosis, chromosomal anomaly, premature birth, emergent caesarean section, and instrumental labor requiring obstetric intervention [11-16]. In other words, even though pregnant women and their newborn babies may be in good condition, late childbearing can result in a higher frequency of pregnancy complications (premature birth, presentation, pregnancy induced hypertension, gestational diabetes, placenta previa, and premature rupture of membranes), myoma of the uterus, and low birth weight infants [17]. However, there have not been many studies regarding the nutritional risk factors and nutritional status of elderly gravida. For this reason, nutritional support and specific management systems for elderly gravida have not been systematically established. Therefore, if we are able to establish systematic nutrition management for elderly gravida, it will lead to management of new-born nutrition. This systematic nutrition management will become a core field of application for establishing Korean health policy goals and will expand future growth drives through improved public health.

This study compared nutrient intakes, lifestyle habits, serum iron index values, and pregnancy outcomes between young and advanced aged pregnant women to provide groundwork for improving the nutritional status of pregnant women and their babies.

The purpose of this research was to determine the daily lifestyles, nutrient intakes, blood iron indices, and differences in pregnancy outcomes of pregnant women according to age. The only daily lifestyle factor that showed an attentive difference was experience and duration of drinking alcohol prior to pregnancy. Sayal [18] reported that if a pregnant woman drinks more than 4 glasses of alcohol per day, risk to the embryo's behavior and mental health increases, and if a woman drinks every day prior to pregnancy, there is a high risk of presenting hyperactivity and carelessness during pregnancy [18]. Yang et al. [19] observed that drinking alcohol during pregnancy strongly affected abruption of the placenta [19]. Among the research subjects, there were no women who drank while they were pregnant, but some women in the YP group showed high alcohol intakes prior to pregnancy; therefore, active nutrition education and promotion of refraining from drinking during pregnancy are necessary.

The daily average energy intake of the subjects was 1,840.8 ± 774.46 kcal, which was about 80% of the estimated necessary energy intake for pregnant women according to the Dietary Reference Intakes for Koreans 2005 (KDRI) [20]; the YP group showed an energy intake of 83% and the AP group showed an intake of 75% of the DRI, respectively. Protein intake was 142% of the DRI in the YP group and 136% in the AP group. Except for niacin intake, which was considerably higher in the YP group than in the AP group (P < 0.05), no nutrients showed significant intake differences. The nutrients consumed below the average requirements according to the KDRIs were energy (YP 83% : AP 75%), calcium (YP 75% : AP 75%), potassium (YP 60% : AP 58%), and folic acid (YP 62% : AP 69%).

It has been reported that if folate intake is insufficient in the early stage of pregnancy, then the risk of birth defects such as neural tube defects (NTD) will be higher [21]. Kim and Lee [22] reported that Korean women tend to show low intake levels of folate prior to pregnancy and after birth [22]. Folate is the most necessary nutrient in the early stage of pregnancy (21-28 days after pregnancy), and it is strongly recommended that fertile women who are older in age and planning pregnancy regularly consume folate prior to pregnancy.

Guelinckx [23] reported that vegetable intake can be increased simply by reading a brochure for nutrition intervention through nutrition counseling with a nutritionist [23]. Nutrition intervention including nutrition education brochures, video materials, and nutrition counseling, should be reviewed from various standpoints before and during pregnancy.

The iron intakes from food for the YP and AP pregnancy groups were 18% and 19%, respectively, and the women consumed 80% of their iron from supplements. Their total iron intakes were 80.24 ± 29.87 mg and 77.23 ± 28.84 mg, respectively, which were 1.8 and 1.7 times higher than the upper intake of 45 mg in the KDRIs. A similar result was reported by Jang and Ahn [24] in that pregnant women in Korea consumed excess iron.

To prevent an iron deficiency during pregnancy, most pregnant women take iron supplements. Appropriate iron supplement intake increases iron status during pregnancy and after childbirth and also increases hemoglobin content in pregnant women [25] [26]. In addition, it increases birth weight in infants and consequently decreases the risk of delivering a child of low birth weight [27].

However, it was reported that excessive iron intake from supplements may cause harmful effects in the immune response of pregnant women [28]. Therefore, excess iron intake is not desirable for successful pregnancy outcomes.

Moreover, it was reported that excessive iron intake may prevent the absorption of other small amounts of inorganic substances and derive negative effects in oxidization pathways resulting in negative symptoms such as increased oxidative stress, constipation, and impaired judgment. Therefore, the appropriate amount of iron to supplement during pregnancy is still under dispute [29]. When pregnant women consume iron excessively and then stop iron supplements after birth, it can lead to concern, such that a woman who delivers a child can show iron deficiency symptoms even though she is in a normal nutritive state for iron. Therefore, it is essential to create an appropriate dietary strategy to implement proper iron intake from meals during pregnancy and discuss the risk of surplus iron from supplements during pregnancy.

In the case of increased calcium intake during pregnancy, it was previously found that exposed infants had increased bone mass when they reached 9 years old [30]. The result of this study emphasizes the importance of appropriate calcium intake. As a result, it is necessary to plan dietary menus with sufficient calcium and to perform appropriate amounts of outdoor exercise during pregnancy.

By interpreting a table for the iron status of the pregnant women, each separate item was at a normal level and there were no large differences between the YP and AP groups. For Hg and HCT, values were 11.5-16.9 g/dl and 36-46%, respectively, which were lower than for average adult women. However, the standards determined by WHO [31] for anemia in pregnant women are < 11.0 g/dl for Hg and > 33.0% for HCT, which can lead to the conclusion that the pregnant women with 11.5-16.9 g/dl Hg and 36-46% HCT did not have symptoms of anemia. In terms of pregnancy outcomes, there were no differences between the two groups for infant birth weight and height, Apgar score, pregnancy duration, or weight gain of the mother. According to Lee et al. [32], as a mother's age increases, she is likely to have an infant of low birth weight; however, this can be overcome by education, marriage status, and race.

The result of no significant difference in pregnancy outcomes according to mother's age, could lead to two possible conclusions. First, even though a woman may be of advanced age to have a baby, if she is able to maintain healthy habits before and during pregnancy then good pregnancy outcomes can be expected. Second, the result might be due to the small age gap between the two age groups. The average ages of the two groups were only about 6 years apart. Therefore, increasing the age difference between these two groups of pregnant women would present better results.

During pregnancy, woman who exercised 1-3 times a month gave birth to babies of lower weight than woman who exercised 1-3 times a week or did not exercise. Because the number of pregnant women who exercised 1-3 times a month was only 4 persons, we deem that other unobserved personal factors affected infant birth weight. In conclusion, pregnant women, even of advanced age, can obtain desirable pregnancy outcomes if they engage in healthy daily life-style habits, including optimal intakes of folate and calcium.