Preconception Blood Pressure and Risk of Low Birth Weight and Small for Gestational Age

Association of pre-/early pregnancy high blood pressure and pregnancy outcomes: a systemic review and meta-analysis

BACKGROUND

Maternal high blood pressure (BP) was associated with adverse pregnancy outcomes. This study aimed to synthesize evidence on the association between high BP prior to or in early pregnancy with maternal and fetal complications.

METHODS

We searched the cohort studies assessing the effect of high BP in the Medline, Embase, Web of Science and China National Knowledge Internet databases. A random-effects model was used to estimate the pooled odds ratios (ORs) with 95% confidence intervals (CIs). The protocol was registered in PROSPERRO (CRD 42023414945).

RESULTS

23 eligible studies were identified. High BP prior to or in early pregnancy was associated with higher odds of hypertensive disorders of pregnancy (OR 2.90, 95% CI 1.91-3.89), gestational hypertension (2.56, 2.01-3.12), preeclampsia (3.20, 2.66-3.74), gestational diabetes mellitus (1.71, 1.36-2.06), preterm birth (1.66, 1.39-1.93), stillbirth (2.01, 1.45-2.58) and neonatal intensive care unit admission (1.22, 1.08-1.37). Subgroup analyses indicated that pre-hypertension could significantly increase the odds of these outcomes except for stillbirth, though the odds were lower than hypertension.

CONCLUSIONS

High BP prior to or in early pregnancy was associated with adverse pregnancy outcomes and this association increased with hypertension severity. The findings emphasized an urgent need for heightened surveillance for maternal BP, especially pre-hypertensive status.

Preconception Blood Pressure and Adverse Pregnancy Outcomes: A Population-Based Cohort Study

BACKGROUND

Adverse pregnancy outcomes (APOs) share clinical features and risk factors with cardiovascular disease and there is an increasing prevalence of hypertension among reproductive women. However, the associations between maternal preconception blood pressure (BP) and APOs remain controversial and inconclusive.

METHODS

This population-based cohort study used data of 567 127 mother-neonate-father triads from the National Free Preconception Checkup Project in Guangdong Province, China. Maternal BP levels within 1 year before pregnancy were classified using the American College of Obstetricians and Gynecologists definition of hypertension. The primary outcome was a composite of APOs, including preterm birth, small for gestational age, and perinatal infant death. Log-binomial and marginal structural binomial regressions were employed to estimate adjusted risk ratios and absolute risk differences, respectively.

RESULTS

Compared with women with normal BP, women with elevated BP (adjusted risk ratio, 1.07 [95% CI, 1.05-1.09]; absolute risk difference, 1.03% [95% CI, 0.72%-1.29%]), hypertension (adjusted risk ratio, 1.25 [95% CI, 1.18-1.32]; and absolute risk difference, 3.42% [95% CI, 1.97%-5.42%]) had a higher risk of a composite of APOs. Compared with women with normal BP, women with elevated BP and hypertension had higher risks of multiple APOs, preterm birth, small for gestational age, and perinatal infant death. However, these associations attenuated with increasing duration of pregnancy preparation and were not statistically significant beyond 90 days of pregnancy preparation.

CONCLUSIONS

Women with elevated BP or hypertension before pregnancy were associated with an increased risk of APOs. Preconception hypertension screening and control among women should not be ignored by policymakers, clinicians, and the general population.

Risk factors and glycaemic control in small-for-gestational-age infants born to mothers with gestational diabetes mellitus: a case-control study using propensity score matching based on a large population

BACKGROUND

Small for gestational age (SGA) poses a significant concern for newborns, being linked to neonatal complications and potential metabolic disorders in adulthood, especially when born to mothers with gestational diabetes mellitus (GDM), elevating their risk of complications and mortality. However, the pregnancy risk factors and glycaemic control associated with SGA infants born to mothers with GDM remain unclear.

AIM

To identify the pregnancy risk factors and glycaemic control associated with SGA infants born to mothers with GDM.

METHOD

This case-control study was conducted among 1910 women with GDM in China. Data were collected by the integrated electronic medical record system. Using 1:4 propensity score matching analysis, we adjusted for gestational age as confounder. Univariate and multivariate analyses were performed to identify risk factors.

RESULTS

Risk factors for SGA born to mothers with GDM included a history of low birth weight, gestational hypertension, oligohydramnios, short maternal height, underweight pre-pregnancy body mass index and inadequate weight growth. While SGA was protected by weakly positive ketonuria levels in the first trimester, multiparous, anaemia and previous uterine scar were protective factors for SGA. Moreover, 2-hour postprandial glucose and haemoglobin A1c in the second trimester, as well as the 0-hour and 2-hour 75 g oral glucose tolerance test (OGTT) were linked to risk of SGA.

CONCLUSIONS

SGA infants are the result of multifactorial interactions among GDM pregnant women. Notably, glycaemic control levels were associated with SGA. There is a need for enhanced perinatal monitoring and antenatal care to reduce SGA.

Maternal diet quality during pregnancy and its influence on low birth weight and small for gestational age: a birth cohort in Beijing, China

This study aimed to describe diet quality of pregnant women and explore the association between maternal diet and the prevalence of low birth weight (LBW) and small for gestational age (SGA). A total of 3856 participants from a birth cohort in Beijing, China, were recruited between June 2018 and February 2019. Maternal diet in the first and second trimesters was assessed by the Chinese diet balance index for pregnancy (DBI-P), using data collected by the inconsecutive 2-d 24-h dietary recalls. Logistic regressions were performed to explore the independent effects of DBI-P components on LBW and SGA. The prevalence of LBW and SGA was 3·8% and 6·0%, respectively. Dietary intakes of the participants were imbalanced. The proportions of participants having insufficient intake of vegetables (87·3% and 86·6%), dairy product (95·9% and 96·7%) and aquatic foods (80·5% and 85·3%) were high in both trimesters. The insufficiency of fruit intake was more severe in the second (85·2%) than that in the first trimester (22·5%) (P < 0·05). After adjusting for potential confounders, the intake of fruits and dairy in the second trimester was negatively associated with the risk of LBW (OR = 0·850, 95% CI: 0·723, 0·999) and SGA (OR = 0·885, 95% CI: 0·787, 0.996), respectively. Sufficient consumption of fruits and dairy products in pregnancy may be suggested in order to prevent LBW and SGA.

Maternal Hypertension Increases Risk of Preeclampsia and Low Fetal Birthweight: Genetic Evidence From a Mendelian Randomization Study

BACKGROUND

Maternal cardiovascular risk factors have been associated with adverse maternal and fetal outcomes. Given the difficulty in establishing causal relationships using epidemiological data, we applied Mendelian randomization to explore the role of cardiovascular risk factors on risk of developing preeclampsia or eclampsia, and low fetal birthweight.

METHODS

Uncorrelated single-nucleotide polymorphisms associated systolic blood pressure (SBP), body mass index, type 2 diabetes, LDL (low-density lipoprotein) with cholesterol, smoking, urinary albumin-to-creatinine ratio, and estimated glomerular filtration rate at genome-wide significance in studies of 298 957 to 1 201 909 European ancestry participants were selected as instrumental variables. A 2-sample Mendelian randomization study was performed with primary outcome of preeclampsia or eclampsia (PET). Risk factors associated with PET were further investigated for their association with low birthweight.

RESULTS

Higher genetically predicted SBP was associated increased risk of PET (odds ratio [OR] per 1-SD SBP increase 1.90 [95% CI=1.45-2.49]; P=3.23×10-6) and reduced birthweight (OR=0.83 [95% CI=0.79-0.86]; P=3.96×10-18), and this was not mediated by PET. Body mass index and type 2 diabetes were also associated with PET (respectively, OR per 1-SD body mass index increase =1.67 [95% CI=1.44-1.94]; P=7.45×10-12; and OR per logOR increase type 2 diabetes =1.11 [95% CI=1.04-1.19]; P=1.19×10-3), but not with reduced birthweight.

CONCLUSIONS

Our results provide evidence for causal effects of SBP, body mass index, and type 2 diabetes on PET and identify that SBP is associated with reduced birthweight independently of PET. The results provide insight into the pathophysiological basis of PET and identify hypertension as a potentially modifiable risk factor amenable to therapeutic intervention.

Stage 1 hypertension defined by the 2017 American College of Cardiology/American Heart Association guideline and risk of adverse birth outcomes in Eastern China

OBJECTIVE

The 2017 American College of Cardiology/American Heart Association (ACC/AHA) guideline recommended a lower threshold (130/80 mmHg) for hypertension in nonpregnant adults. However, the influence of this guideline in Chinese pregnant women is not well characterized.

METHODS

Data of 32 742 and 14 479 mothers who had blood pressure (BP) less than 130/80 mmHg and no proteinuria before 20 gestational weeks and delivered live singletons between 1 January 2014 and 30 November 2019 were extracted from Taizhou and Taicang register-based cohorts, respectively. The average measured BP in the third trimester was obtained and categorized according to the 2017 ACC/AHA guideline. The association between BP and risk of adverse birth outcomes was assessed by multivariate logistic regression analysis.

RESULTS

In the third trimester, 331 (1.01%) and 378 (2.61%) women had mean BP at least 140/90 mmHg, but 2435 (7.44%) and 1054 (7.28%) had stage 1 hypertension (130-139/80-89 mmHg) in Taizhou and Taicang, respectively. Significant associations between stage 1 hypertension and small for gestational age [odds ratio (OR) = 1.32, 95% confidence interval (CI) = 1.14-1.52] and low birth weight (OR = 1.81, 95% CI = 1.46-2.25) were observed in the Taizhou population. Consistent results were also shown in the Taicang population [OR (95% CI), of 1.46 (1.18-1.79) and 1.50 (1.07-2.11), respectively].

CONCLUSION

Stage 1 hypertension in the third trimester defined by the 2017 ACC/AHA guideline was associated with an increased risk for adverse birth outcomes in Eastern Chinese pregnant women, suggesting that this guideline may improve the detection of high BP and surveillance of adverse neonatal outcomes in China.

Impact of gestational hypertension and preeclampsia on low birthweight and small-for-gestational-age infants in China: A large prospective cohort study

Studies have shown that maternal blood pressure level is associated with neonatal birthweight, but the results are not exactly consistent. As the most common hypertensive disorders during pregnancy, the mechanism of gestational hypertension and pre‐eclampsia that affect fetal growth remain unclear. Our objective was to examine the association of gestational hypertension and pre‐eclampsia with the risk of low birthweight (LBW) and small‐for‐gestational‐age (SGA). Data were obtained from the China–US Collaborative Project for Neural Tube Defects Prevention, a large population‐based cohort study. We selected participants who were registered in two southern provinces, had exact information on gestational blood pressure and pregnancy outcomes, and were not affected by chronic hypertension. Logistic regression was used to adjust for the effects of the main potential confounders, including age, body mass index, education, occupation, ethnicity, folic acid use, and parity. The overall incidences of LBW and SGA were 2.25% and 5.86%, respectively. The incidences of LBW/SGA were 3.58%/7.58% and 6.02%/10.67% for gestational hypertension and pre‐eclampsia group, relative to 2.11%/5.68% and 2.16%/5.74% for normal group. The adjusted odds ratios associated with gestational hypertension/pre‐eclampsia were 1.77 (95% CI: 1.63, 1.92)/3.01 (95% CI: 2.67, 3.40) for LBW and 1.40 (95% CI: 1.32, 1.48)/2.02 (95% CI: 1.84, 2.22) for SGA, respectively. The early onset of gestational hypertension/pre‐eclampsia appeared to be a relatively more detrimental exposure window for both LBW and SGA. Our results support an association between gestational hypertension or pre‐eclampsia and the increased risk of LBW and SGA.

Long-term exposure to airborne particulate matter of 1 μm or less and blood pressure in healthy young adults: A national study with 1.2 million pregnancy planners

No evidence exists concerning the effect of airborne particulate matter of 1 μm or less (PM₁) on blood pressure of young adults planning for pregnancy. We collected health examination information of about 1.2 million couples (aged 18-45 years) from a national birth cohort in China from Jan 1, 2013 to Oct 1, 2014 and matched their home address to daily PM₁ and PM_2.5 concentrations, which were predicted by remote sensing information. Generalized additive mixed models were used to analyze associations between long-term exposure to PM and blood pressure, after controlling for individual factors. A 10 μg/m³ increase in PM₁ was associated with increased systolic blood pressure (SBP) for 0.26 (95%CI: 0.24, 0.29) mmHg in females and 0.29 (95%CI: 0.26, 0.31) mmHg in males, respectively. PM₁ was also associated with increased DBP for 0.22 (95%CI: 0.20, 0.23) mmHg in females and 0.17 (95%CI: 0.15, 0.19) mmHg in males, respectively. Similar effects on blood pressure were found for PM_2.5, meanwhile, the effect of PM_2.5 on SBP increased with the scale of PM₁ included in PM_2.5 (p for interaction term <0.01). In summary, long-term exposure to PM₁ as well as PM_2.5 was associated with increased SBP and DBP of Chinese young adults planning for pregnancy.

Preconception blood pressure and risk of gestational hypertension and preeclampsia: a large cohort study in China

Our objective was to examine whether high blood pressure in the preconception period was associated with gestational hypertension and preeclampsia in Chinese women. Data were obtained from the China-US Collaborative Project for Neural Tube Defects Prevention, a large population-based cohort study. We included 45,628 women who were registered before pregnancy in seven counties in South China. Blood pressure was measured during registration by trained health care workers, and other health-related information was recorded prospectively. We used logistic regression to evaluate the associations between preconception blood pressure and the risk of gestational hypertension and preeclampsia, adjusting for potential confounders. The prevalence of hypertension in the preconception study population was 4.57% (2083/45,628). The incidences of gestational hypertension and preeclampsia were 11.95% and 4.08%, respectively, in the hypertension group and 8.60% and 2.28%, respectively, in the nonhypertension group. Compared with the nonhypertension group, the hypertension group showed a significantly increased risk for gestational hypertension [adjusted risk ratio (RR) = 1.40, 95% confidence interval (CI): 1.22-1.60] and preeclampsia [adjusted RR = 1.75, 95% CI: 1.39-2.19]. When participants with normal blood pressure were used as the reference, the adjusted ORs for gestational hypertension were 1.48 (95% CI: 1.37-1.59), 1.70 (95% CI: 1.44-2.01), and 1.29 (95% CI: 1.02-1.64), and for preeclampsia, the adjusted ORs were 1.55 (95% CI: 1.35-1.78), 1.95 (95% CI: 1.46-2.60), and 1.99 (95% CI: 1.39-2.85) for the participants with prehypertension, stage 1 hypertension, and stage 2 hypertension, respectively. Our results support an association between hypertension or higher blood pressure prior to pregnancy and an increased risk of gestational hypertension and preeclampsia.

The management of hypertension in women planning for pregnancy

INTRODUCTION OR BACKGROUND

Poorly-controlled hypertension in the first trimester significantly increases maternal and fetal morbidity and mortality. The majority of guidelines and clinical trials focus on the management and treatments for hypertension during pregnancy and breast-feeding, while limited evidence could be applied to the management for hypertension before pregnancy. In this review, we summarized the existing guidelines and treatments of pre-pregnancy treatment of hypertension.

SOURCES OF DATA

PubMed.

AREAS OF AGREEMENT

Methyldopa and labetalol are considered the first choice, but angiotensin-converting enzyme (ACE) inhibitors and angiotensin receptor blockers (ARBs) need to be withdrawn if a hypertensive woman wishes to become pregnant. In women with chronic hypertension, it is very important to make an assessment before conception to exclude secondary causes of hypertension, evaluate their hypertensive control to ensure that it is optimal, discuss the increased risks of pre-eclampsia, and provide education regarding any drug alterations before they become pregnant.

AREAS OF CONTROVERSY

There is increasing debate regarding discouraging the use of diuretics. There is also controversy regarding the use of supplementations such as calcium, antioxidants and low-dose aspirin.

GROWING POINTS

A less restricted blood-pressure goal could be set for hypertensive women planning for pregnancy. A healthy body weight before pregnancy could lower the risk of pregnancy-related hypertensive disorders. Recent guidelines also encourage women with chronic hypertension to keep their dietary sodium intake low, either by reducing or substituting sodium salt before pregnancy.

TIMELY AREAS FOR DEVELOPING RESEARCH

Large, worldwide, randomized trials should be conducted to see the outcomes for hypertensive women who take antioxidants/physical activity before pregnancy.

Dose-response relationship between maternal blood pressure in pregnancy and risk of adverse birth outcomes: Ma'anshan birth cohort study

OBJECTIVES

This study depicts the dose-response relationship between blood pressure (BP) during pregnancy and adverse birth outcomes in different trimesters.

STUDY DESIGN

We used restricted cubic spline to quantify the dose-response relationship between maternal BP in different trimesters and risk of adverse birth outcomes (small for gestational age, SGA; and pre-term birth, PTB). The data were from the Ma'anshan birth cohort study in China (N = 3273).

MAIN OUTCOME MEASURES

Risk of SGA and PTB.

RESULTS

There were dose-response associations of both systolic blood pressure (SBP) and diastolic blood pressure (DBP) with risk of SGA in the third trimester and with PTB in both second and third trimesters. In the third trimester, compared with SBP of 120 mmHg, the odds ratios (ORs) and 95% confidence intervals (CI) of SGA were 1.12 (1.01-1.19), 1.32 (1.10-1.60), 1.65 (1.20-2.27) and 2.05 (1.30-3.24) for SBP of 125, 130, 135 and 140 mmHg, respectively. The corresponding ORs and 95% CIs of PTB were 1.15 (1.00-1.32), 1.59 (1.28-1.98), 2.35 (1.66-3.33) and 3.47 (2.10-5.73), respectively. Compared with DBP of 70 mmHg, the ORs and 95% CIs of SGA were 1.44 (1.16-1.78) and 3.04 (2.06-4.50) for DBP of 80 and 90 mmHg, respectively. The corresponding ORs and 95% CIs of PTB were 1.32 (0.93-1.90) and 3.58 (2.21-5.78), respectively.

CONCLUSIONS

A consistent set of dose-response relationships between maternal BP and adverse birth outcomes were observed. Most importantly, we found that moderately elevated maternal BP, even within a normal range, increased the risk of adverse birth outcomes.