Birth weight centiles and small for gestational age by sex and ethnicity for England and Wales

Maternal positional therapy for fetal growth and customised birth weight centile benefit in a Bayesian reanalysis of a double-blind, sham-controlled, randomised clinical trial

OBJECTIVES

To update the Ghana PrenaBelt Trial's (GPT) primary outcome data with the latest fetal growth standard and reanalyse it. To estimate the posterior probability, under various clinically relevant prior probabilities, of maternal nightly positional therapy (PT) throughout the third-trimester having a beneficial effect on customised birth weight centile (CBWC) using Bayesian analyses.

DESIGN

A reanalysis of a double-blind, sham-controlled, randomised clinical trial.

SETTING

A single, tertiary-level centre in Accra, Ghana.

PARTICIPANTS

Two-hundred participants entered, 181 completed and 167 were included in the final analysis. Participants were Ghanaian, healthy, aged 18-35 years, with low-risk, singleton pregnancies in their third-trimester, with Body Mass Index<35 kg/m2 at the first antenatal appointment for the index pregnancy and without known fetal abnormalities, pregnancy complications or medical conditions complicating sleep.

INTERVENTIONS

Participants were randomised to receive treatment with either a PT or sham-PT device.

PRIMARY AND SECONDARY OUTCOME MEASURES

The primary outcome was the CBWC using the latest Perinatal Institute, Gestation-Related Optimal Weight calculator. Using Bayesian methods, posterior probabilities of achieving a greater than 0%, 5% and 10% benefit in CBWC with PT were estimated. There was no secondary outcome.

RESULTS

The median (IQR) CBWC was 42% (15-71) and 28% (9-52) in the PT and sham-PT groups, respectively (difference 8.4%; 95% CI -0.30 to 18.2; p=0.06). For achieving a >0%, >5% and >10% gain in CBWC with PT, the posterior probabilities were highly probable, probable and unlikely, respectively, given a range of prior probabilities reflecting varying degrees of pre-existing enthusiasm and scepticism.

CONCLUSIONS

Maternal nightly PT throughout the third-trimester did not have a statistically significant effect on CBWC on a frequentist analysis using the latest fetal growth standard. However, from a Bayesian analysis, clinicians can infer that PT is likely to benefit fetal growth but with a modest effect size.

TRIAL REGISTRATION NUMBER

NCT02379728.

Temporal trends and risk of small for gestational age (SGA) infants among Asian American mothers by ethnicity

PURPOSE

To examine the temporal trends and risk of small for gestational age (SGA) phenotypes across Asian American ethnic groups.

METHODS

We conducted a population-based retrospective study using the 1992-2018 natality data files obtained from the National Vital Statistics System. Joinpoint regression modeling was employed to calculate the average annual percentage change in SGA birth rates among Asian American sub-groups and NH-White women. Logistic regression was utilized to compute the adjusted odds ratio and 95% confidence interval for the association between maternal race (Asian American sub-groups vs. NH-White) and SGA birth and its phenotypes.

RESULTS

We analyzed data on 2,821,798 Asian Americans and 62,174,875 NH-White US live-born infants. Overall, NH-Whites had the lowest SGA rates, while all the Asian ethnic groups had almost consistently higher rates during the 27-year period. Disparity in SGA births in the Asian subgroups was observed. Compared to NH-Whites, stratified analyses showed varying and significantly higher odds of any SGA in all Asian ethnic groups. Asian Indians had the highest odds [adjusted odds ratio (AOR) = 2.23, 95% confidence interval (CI) = 2.22-2.23] of any SGA compared to NH-Whites.

CONCLUSIONS

Our findings support the evidence that Asian Americans are not a homogenous group and highlight the need to disentangle these differences when conducting population health research and interventions among Asian Americans.

Association of Supine Going-to-Sleep Position in Late Pregnancy With Reduced Birth Weight: A Secondary Analysis of an Individual Participant Data Meta-analysis

IMPORTANCE

Supine maternal position in the third trimester is associated with reduced uterine blood flow and increased risk of late stillbirth. As reduced uterine blood flow is also associated with fetal growth restriction, this study explored the association between the position in which pregnant women went to sleep and infant birth weight.

OBJECTIVE

To examine the association between supine position when going to sleep in women after 28 weeks of pregnancy and lower birth weight and birth weight centiles.

DESIGN, SETTING, AND PARTICIPANTS

Prespecified subgroup analysis using data from controls in an individual participant data meta-analysis of 4 case-control studies investigating sleep and stillbirth in New Zealand, Australia, and the United Kingdom. Participants were women with ongoing pregnancies at 28 weeks' gestation or more at interview.

MAIN OUTCOMES AND MEASURES

The primary outcome was adjusted mean difference (aMD) in birth weight. Secondary outcomes were birth weight centiles (INTERGROWTH-21st and customized) and adjusted odds ratios (aORs) for birth weight less than 50th and less than 10th centile (small for gestational age) for supine vs nonsupine going-to-sleep position in the last 1 to 4 weeks, adjusted for variables known to be associated with birth size.

RESULTS

Of 1760 women (mean [SD] age, 30.25 [5.46] years), 57 (3.2%) reported they usually went to sleep supine during the previous 1 to 4 weeks. Adjusted mean (SE) birth weight was 3410 (112) g among women who reported supine position and 3554 (98) g among women who reported nonsupine position (aMD, 144 g; 95% CI, -253 to -36 g; P = .009), representing an approximate 10-percentile reduction in adjusted mean INTERGROWTH-21st (48.5 vs 58.6; aMD, -10.1; 95% CI, -17.1 to -3.1) and customized (40.7 vs 49.7; aMD, -9.0; 95% CI, -16.6 to -1.4) centiles. There was a nonsignificant increase in birth weight at less than the 50th INTERGROWTH-21st centile (aOR, 1.90; 95% CI, 0.83-4.34) and a 2-fold increase in birth weight at less than the 50th customized centile (aOR, 2.12; 95% CI, 1.20-3.76). Going to sleep supine was associated with a 3-fold increase in small for gestational age birth weight by INTERGROWTH-21st standards (aOR, 3.23; 95% CI, 1.37-7.59) and a nonsignificant increase in small for gestational age birth weight customized standards (aOR, 1.63; 95% CI, 0.77-3.44).

CONCLUSIONS AND RELEVANCE

This study found that going to sleep in a supine position in late pregnancy was independently associated with reduced birth weight and birth weight centile. This novel association is biologically plausible and likely modifiable. Public health campaigns that encourage women in the third trimester of pregnancy to settle to sleep on their side have potential to optimize birth weight.