Comparison of alternative gestational age assessment methods in a low resource setting: a retrospective study

BMC Pregnancy and Childbirth, Volume 22, No. 1, Year 2022

Interpretation

Background: Accurate gestational age (GA) determination allows correct management of high-risk, complicated or post-date pregnancies and prevention or anticipation of prematurity related complications. Ultrasound measurement in the first trimester is the gold standard for GA determination. In low- and middle-income countries elevated costs, lack of skills and poor maternal access to health service limit the availability of prenatal ultrasonography, making it necessary to use alternative methods. This study compared three methods of GA determination: Last Normal Menstrual Period recall (LNMP), New Ballard Score (NBS) and New Ballard Score corrected for Birth Weight (NBS + BW) with the locally available standard (Ultrasound measurement in the third trimester) in a low-resource setting (Tosamaganga Council Designated Hospital, Iringa, Tanzania). Methods: All data were retrospectively collected from hospital charts. Comparisons were performed using Bland Altman method. Results: The analysis included 70 mother-newborn pairs. Median gestational age was 38 weeks (IQR 37–39) according to US. The mean difference between LNMP vs. US was 2.1 weeks (95% agreement limits − 3.5 to 7.7 weeks); NBS vs. US was 0.2 weeks (95% agreement limits − 3.7 to 4.1 weeks); NBS + BW vs. US was 1.2 weeks (95% agreement limits − 1.8 to 4.2 weeks). Conclusions: In our setting, NBS + BW was the least biased method for GA determination as compared with the locally available standard. However, wide agreement bands suggested low accuracy for all three alternative methods. New evidence in the use of second/third trimester ultrasound suggests concentrating efforts and resources in further validating and implementing the use of late pregnancy biometry for gestational age dating in low and middle-income countries. This study was carried out at the St. John of the Cross Hospital of Tosamaganga (Iringa, Tanzania), the only Comprehensive Emergency Obstetric and Newborn Care Center in Iringa Rural District. Designated as referral hospital of Iringa Rural District Council, it serves an estimated population of 265 000 inhabitants, handling approximately 2300 deliveries per year. The hospital has a total of 165 beds, 48 of which are in the maternity department, including 12 obstetrics, 18 in vaginal postpartum and 18 in CS postpartum. A labour room, a neonatal resuscitation room and a Neonatal Special Care Unit are also present [10]. All the mother-newborn pairs with complete data on the three different methods of determining GA were included in the study. The agreement in GA estimation between different methods. All data were retrospectively and anonymously collected from hospital charts and did not contain any information that might be used to identify individual patients. Maternal data included: age, weight, BMI, number of pregnancies, mode of delivery, GA by LNMP recall, GA by ultrasound measurement in the third trimester. Neonatal data included: sex, birth weight, APGAR score, GA by NBS and NBS + BW. The GA refers to the duration of time between conception and delivery. The LNMP recall is the difference between the first day of the last menstrual period and the delivery date. A US is defined as of the third trimester when executed at 28 0/7 weeks of gestation and beyond [1]. Late ultrasound GA determination was performed using the INTERGROWTH-21st project estimation method [11]. The NBS consists in a procedure, performed postnatally up to 96 h after birth, that asses physical and neuromuscular maturity of the neonate to determine its gestational age [12]. NBS + BW refers to the NBS adjusted considering birth weight in the score calculation [9]. The US measurement in the third trimester was separately compared with LNMP recall, NBS and NBS + BW. The sample size calculation was based on information from available literature [8]. Assuming a mean difference of 0 weeks with a standard deviation of 3 weeks, a minimum of 64 subjects were required to have an 80% chance of detecting, as significant at the 5% level, an agreement interval of 8 weeks in the Bland-Altman plot. The final sample size was rounded up to 70 subjects (reaching an estimated power of 85%). Sample size calculation was performed using R 4.1 (R Foundation for Statistical Computing, Vienna, Austria) [13]. Categorical variables were summarized as frequency and percentage. Continuous variables were summarized as mean and standard deviation (SD) or median and interquartile range (IQR). The agreement in GA estimation between different methods was assessed using Bland Altman plot (showing mean difference and 95% agreement limits). The correlation between continuous variables was assessed using Pearson correlation coefficient. Inter-rater reliability between the clinicians was evaluated using intra-class correlation coefficient (ICC) in a subsample of 30 newborns with double assessments. All tests were two-sided and a p-value less than 0.05 was considered statistically significant. Statistical analysis was performed using R 4.1 (R Foundation for Statistical Computing, Vienna, Austria) [13].

AI Digest

Study Justification:

Accurate determination of gestational age (GA) is crucial for managing high-risk pregnancies and preventing complications related to prematurity. However, in low-resource settings, the availability of prenatal ultrasonography is limited due to cost, lack of skills, and poor access to healthcare. Therefore, alternative methods for GA determination are necessary. This study aimed to compare three alternative methods (Last Normal Menstrual Period recall, New Ballard Score, and New Ballard Score corrected for Birth Weight) with the standard ultrasound measurement in the third trimester in a low-resource setting.

Study Highlights:

– The study was conducted at the St. John of the Cross Hospital of Tosamaganga in Iringa, Tanzania, which serves as the only Comprehensive Emergency Obstetric and Newborn Care Center in the area.
– Data from 70 mother-newborn pairs were retrospectively collected from hospital charts.
– The analysis showed that the New Ballard Score corrected for Birth Weight (NBS + BW) was the least biased method for GA determination compared to the locally available standard (ultrasound measurement in the third trimester).
– However, all three alternative methods had low accuracy, as indicated by wide agreement bands.
– The study suggests further validation and implementation of late pregnancy biometry using ultrasound for gestational age dating in low and middle-income countries.

Recommendations for Lay Reader:

– The study compared different methods of determining gestational age in a low-resource setting.
– The New Ballard Score corrected for Birth Weight was found to be the most accurate alternative method.
– However, all alternative methods had limitations in accuracy.
– The study recommends further research and implementation of late pregnancy ultrasound for gestational age dating in low-income countries.

Recommendations for Policy Maker:

– The study highlights the challenges of accurate gestational age determination in low-resource settings.
– The New Ballard Score corrected for Birth Weight showed the most promise as an alternative method.
– However, more resources and efforts are needed to validate and implement the use of late pregnancy ultrasound for gestational age dating.
– Policy makers should consider allocating funds and resources to improve access to prenatal ultrasonography and training healthcare providers in low-income countries.

Key Role Players:

– Healthcare providers: Trained professionals who can perform ultrasound measurements and alternative methods for gestational age determination.
– Policy makers: Individuals responsible for allocating resources and implementing policies to improve access to prenatal care and ultrasound services.
– Researchers: Experts who can conduct further studies to validate and refine alternative methods for gestational age determination.

Cost Items for Planning Recommendations:

– Training: Budget for training healthcare providers in ultrasound measurement and alternative methods.
– Equipment: Funds for acquiring ultrasound machines and other necessary equipment for accurate gestational age determination.
– Infrastructure: Investment in healthcare facilities to ensure proper infrastructure for prenatal care and ultrasound services.
– Research: Budget for conducting further research to validate and refine alternative methods.
– Outreach and awareness: Funds for outreach programs and awareness campaigns to educate communities about the importance of accurate gestational age determination and the available methods.
Please note that the provided cost items are general suggestions and may vary depending on the specific context and requirements of the implementation.

Strength of Evidence

N/A

Abstract

This study was carried out at the St. John of the Cross Hospital of Tosamaganga (Iringa, Tanzania), the only Comprehensive Emergency Obstetric and Newborn Care Center in Iringa Rural District. Designated as referral hospital of Iringa Rural District Council, it serves an estimated population of 265 000 inhabitants, handling approximately 2300 deliveries per year. The hospital has a total of 165 beds, 48 of which are in the maternity department, including 12 obstetrics, 18 in vaginal postpartum and 18 in CS postpartum. A labour room, a neonatal resuscitation room and a Neonatal Special Care Unit are also present [10]. All the mother-newborn pairs with complete data on the three different methods of determining GA were included in the study. The agreement in GA estimation between different methods. All data were retrospectively and anonymously collected from hospital charts and did not contain any information that might be used to identify individual patients. Maternal data included: age, weight, BMI, number of pregnancies, mode of delivery, GA by LNMP recall, GA by ultrasound measurement in the third trimester. Neonatal data included: sex, birth weight, APGAR score, GA by NBS and NBS + BW. The GA refers to the duration of time between conception and delivery. The LNMP recall is the difference between the first day of the last menstrual period and the delivery date. A US is defined as of the third trimester when executed at 28 0/7 weeks of gestation and beyond [1]. Late ultrasound GA determination was performed using the INTERGROWTH-21st project estimation method [11]. The NBS consists in a procedure, performed postnatally up to 96 h after birth, that asses physical and neuromuscular maturity of the neonate to determine its gestational age [12]. NBS + BW refers to the NBS adjusted considering birth weight in the score calculation [9]. The US measurement in the third trimester was separately compared with LNMP recall, NBS and NBS + BW. The sample size calculation was based on information from available literature [8]. Assuming a mean difference of 0 weeks with a standard deviation of 3 weeks, a minimum of 64 subjects were required to have an 80% chance of detecting, as significant at the 5% level, an agreement interval of 8 weeks in the Bland-Altman plot. The final sample size was rounded up to 70 subjects (reaching an estimated power of 85%). Sample size calculation was performed using R 4.1 (R Foundation for Statistical Computing, Vienna, Austria) [13]. Categorical variables were summarized as frequency and percentage. Continuous variables were summarized as mean and standard deviation (SD) or median and interquartile range (IQR). The agreement in GA estimation between different methods was assessed using Bland Altman plot (showing mean difference and 95% agreement limits). The correlation between continuous variables was assessed using Pearson correlation coefficient. Inter-rater reliability between the clinicians was evaluated using intra-class correlation coefficient (ICC) in a subsample of 30 newborns with double assessments. All tests were two-sided and a p-value less than 0.05 was considered statistically significant. Statistical analysis was performed using R 4.1 (R Foundation for Statistical Computing, Vienna, Austria) [13].

Materials

N/A

Innovations

Based on the information provided, the study titled “Comparison of alternative gestational age assessment methods in a low resource setting: a retrospective study” aimed to evaluate different methods of determining gestational age (GA) in a low-resource setting. The study compared three methods: Last Normal Menstrual Period recall (LNMP), New Ballard Score (NBS), and New Ballard Score corrected for Birth Weight (NBS + BW) with the locally available standard (Ultrasound measurement in the third trimester). The study included 70 mother-newborn pairs, and the results showed that NBS + BW was the least biased method for GA determination compared to the locally available standard. However, all three alternative methods had low accuracy.

In terms of potential innovations to improve access to maternal health, the study suggests further validating and implementing the use of late pregnancy biometry for gestational age dating in low and middle-income countries. This could involve focusing efforts and resources on training healthcare providers in late pregnancy biometry and ensuring access to ultrasound equipment in low-resource settings. Additionally, exploring the use of mobile ultrasound technology or telemedicine consultations could help overcome barriers related to cost and lack of skilled personnel. These innovations have the potential to improve access to accurate gestational age determination, allowing for better management of high-risk pregnancies and prevention of complications.

AI Innovations Description

The study titled “Comparison of alternative gestational age assessment methods in a low resource setting: a retrospective study” aimed to evaluate different methods of determining gestational age (GA) in a low-resource setting to improve access to maternal health. The study compared three methods: Last Normal Menstrual Period recall (LNMP), New Ballard Score (NBS), and New Ballard Score corrected for Birth Weight (NBS + BW) with the locally available standard (Ultrasound measurement in the third trimester).

The study was conducted at the St. John of the Cross Hospital of Tosamaganga in Iringa, Tanzania, which serves as the only Comprehensive Emergency Obstetric and Newborn Care Center in Iringa Rural District. The hospital handles approximately 2300 deliveries per year and has a total of 165 beds, including 48 in the maternity department.

Data for the study were collected retrospectively and anonymously from hospital charts. Maternal data included age, weight, BMI, number of pregnancies, mode of delivery, GA by LNMP recall, and GA by ultrasound measurement in the third trimester. Neonatal data included sex, birth weight, APGAR score, GA by NBS, and GA by NBS + BW.

The results of the study showed that NBS + BW was the least biased method for GA determination compared to the locally available standard. However, all three alternative methods had low accuracy, as indicated by wide agreement bands. The study suggests further validation and implementation of late pregnancy biometry for gestational age dating in low and middle-income countries.

The sample size for the study was 70 mother-newborn pairs, and statistical analysis was performed using R 4.1. Categorical variables were summarized as frequency and percentage, while continuous variables were summarized as mean and standard deviation or median and interquartile range. The agreement between different methods of GA estimation was assessed using Bland Altman plot, and the correlation between continuous variables was evaluated using Pearson correlation coefficient. Inter-rater reliability between clinicians was assessed using intra-class correlation coefficient.

In conclusion, the study recommends focusing efforts and resources on validating and implementing the use of late pregnancy biometry, such as ultrasound, for gestational age dating in low and middle-income countries. This innovation could improve access to maternal health by providing a more accurate method of determining gestational age, allowing for appropriate management of high-risk pregnancies and prevention of complications related to prematurity.

AI Innovations Methodology

The study titled “Comparison of alternative gestational age assessment methods in a low resource setting: a retrospective study” aimed to evaluate different methods of determining gestational age (GA) in a low-resource setting. The study compared three methods: Last Normal Menstrual Period recall (LNMP), New Ballard Score (NBS), and New Ballard Score corrected for Birth Weight (NBS + BW) with the locally available standard (Ultrasound measurement in the third trimester). The methodology involved retrospectively collecting data from hospital charts and performing comparisons using the Bland Altman method.

The study was conducted at the St. John of the Cross Hospital of Tosamaganga in Iringa, Tanzania, which serves as the only Comprehensive Emergency Obstetric and Newborn Care Center in Iringa Rural District. The study included mother-newborn pairs with complete data on the three different methods of determining GA. Maternal data collected included age, weight, BMI, number of pregnancies, mode of delivery, GA by LNMP recall, and GA by ultrasound measurement in the third trimester. Neonatal data included sex, birth weight, APGAR score, GA by NBS, and GA by NBS + BW.

The agreement in GA estimation between different methods was assessed using the Bland Altman plot, which shows the mean difference and 95% agreement limits. The correlation between continuous variables was assessed using the Pearson correlation coefficient. Inter-rater reliability between the clinicians was evaluated using the intra-class correlation coefficient (ICC) in a subsample of 30 newborns with double assessments.

Statistical analysis was performed using R 4.1 (R Foundation for Statistical Computing, Vienna, Austria). Categorical variables were summarized as frequency and percentage, while continuous variables were summarized as mean and standard deviation (SD) or median and interquartile range (IQR). The sample size calculation was based on information from available literature, and the final sample size was rounded up to 70 subjects.

In conclusion, this study compared alternative methods of determining gestational age in a low-resource setting. The results indicated that NBS + BW was the least biased method compared to the locally available standard. However, all three alternative methods showed low accuracy. The study provides valuable insights into the challenges of gestational age assessment in low-resource settings and suggests further validation and implementation of late pregnancy biometry using ultrasound in low and middle-income countries.

Author

Dima Health

Identifiers:

DOI: 10.1186/s12884-022-04914-6

Research Areas:

Community Interventions, Health System and Policy, Maternal Access, Maternal and Child Health, Sexual and Reproductive Health, Social Determinants

Study Countries:

Tanzania

Study Design:

Cohort Study, Cross Sectional Study

Study Approach:

Quantitative