Association of maternal pre-pregnancy low or increased body mass index with adverse pregnancy outcomes

Abstract

This study investigated the association between pre-pregnancy body mass index (BMI) and adverse pregnancy outcomes among women participated in the National Free Preconception Health Examination Project in Guangdong Province, China, and explored these associations according to maternal age. Pre-pregnancy BMI was classified into underweight (BMI < 18.5 kg/m2), healthy weight (18.5–23.9 kg/m2), overweight (24.0–27.9 kg/m2), and obesity (≥ 28.0 kg/m2) according to Chinese criteria. Outcomes were preterm birth (PTB, delivery before 37 weeks of gestation), large for gestational age (LGA, birthweight above the 90th percentile for gestational age by infants’ sex), small for gestational age (SGA, birthweight below the 10th percentile for gestational age by infants’ sex), primary caesarean delivery, shoulder dystocia or birth injury, and stillbirth. Adjusted incidence risk ratios (aIRR) were calculated for underweight, overweight and obesity, respectively. Compared with healthy weight, underweight was associated with increased risk of PTB (aIRR 1.06, 95%CI 1.04–1.09) and SGA (1.23, 1.22–1.26) but inversely associated with LGA (0.83, 0.82–0.85), primary caesarean delivery (0.88, 0.87–0.90) and stillbirth (0.73, 0.53–0.99). Overweight was associated with increased risk of LGA (1.17, 1.14–1.19), primary caesarean delivery (1.18, 1.16–1.20) and stillbirth (1.44, 1.03–2.06), but inversely associated with SGA (0.92, 0.90–0.95) and shoulder dystocia or birth injury (0.86, 0.79–0.93). Obesity was associated with increased risk of PTB (1.12, 1.05–1.20), LGA (1.32, 1.27–1.37), primary caesarean delivery (1.45, 1.40–1.50), but inversely associated with SGA (0.92, 0.87–0.97). The aIRRs for underweight, overweight and obesity in relation to these adverse pregnancy outcomes ranged from 0.65 to 1.52 according to maternal age. In Chinese population, maternal pre-pregnancy BMI was significantly associated with the risk of adverse pregnancy outcomes and the risk differs according to maternal age. Further investigation is warranted to determine whether and how counselling and interventions for women with low or increased BMI before pregnancy can reduce the risk of adverse pregnancy outcomes.

Severity of low pre-pregnancy body mass index and perinatal outcomes: the Japan Environment and Children’s Study

“…The extremes of maternal pre-pregnancy body mass index (BMI) are known to be risk factors associated with obstetric and adverse perinatal outcomes [ 1 – 7 ]. Higher maternal pre-pregnancy BMI increases the risk of hypertensive disorders during pregnancy, gestational diabetes, preterm birth (PTB), fetal death, stillbirth, large-for-gestational age, and macrosomia [ 2 – 7 ]. A lower maternal pre-pregnancy BMI increases the risk of PTB, low birth weight (LBW), and small-for-gestational age (SGA) [ 1 , 3 – 11 ].…”

“…Indeed, the frequency of LBW has been increasing in Japan despite the rate of PTB being as low as 5.6% in 2019 [ 14 ]. Several studies reported that low maternal pre-pregnancy BMI was significantly associated with adverse perinatal outcomes, such as PTB, LBW, and SGA [ 1 , 4 , 5 , 7 – 11 , 15 ]. However, to our knowledge, no studies on the severity of low pre-pregnancy BMI have been conducted in East Asian countries including Japan where pregnancy-aged individuals have a lower BMI compared to other regions.…”

Risk Factors of Pregnancy Failure in Infertile Patients Undergoing Assisted Reproductive Technology

“…Maternal age and paternal age were divided into four subgroups (<30 years, 30–35 years, 36–40 years, and >40 years), respectively. Maternal BMI was divided into four subgroups based on the Chinese criteria: 16 , 17 <18.5 kg/m 2 , 18.5–23.9 kg/m 2 , 24.0–27.9 kg/m 2 , ≥28.0 kg/m 2 . Primary infertility was defined as the failure to achieve pregnancy of a couple after 12 months of regular sexual intercourse without any form of contraception when a woman has never conceived, while secondary infertility was the incapability to conceive in a couple who have had at least one successful clinical pregnancy previously.…”

Maternal Underweight Does Not Adversely Affect The Outcomes of IVF/ICSI and Frozen Embryo Transfer Cycles or Early Embryo Development

“…The body mass index (BMI) is used to identify underweight/overweight of adults and to re ect their nutritional status [1]. The association between overweight/obese (BMI > 25 kg/m 2 ) and impaired fertility [2], worse assisted reproductive technology (ART) outcomes [3][4][5], and increased rates of miscarriage and obstetric risks in spontaneous [6][7][8][9] and ART pregnancies [10][11][12] is well-recognized. Similarly, underweight women (BMI < 18.50 kg/m 2 ) have higher rates of infertility compared to women with a normal BMI (18.…”

“…Additionally, a low BMI is associated with an increased risk of miscarriage in spontaneous pregnancies [14,15] and with higher rates of obstetric complications, such as preterm delivery, preterm premature rupture of membranes, and low birth weight in the general population [9,16,17]. However, as was recently observed in a systematic review and meta-analysis, no association between prepregnancy subnormal body weight and ART outcomes has been established, and the conclusions in the studies conducted to date have been divergent [18].…”