Data Overview

New Hampshire birth conditions data are based upon information obtained as part of an active surveillance system using Centers for Disease Control and Prevention (CDC), National Birth Defects Prevention Network (NBDPN) specified case definitions and trained medical record reviewers for data abstraction. The NBDPN 6-digit code of reportable congenital anomalies based on standard ICD-9 coding is utilized as the standard for reporting data into the surveillance system.

All resident birth data in this report are based upon information provided to the New Hampshire Department of Health and Human Services under specific legislative authority. The data reported represent the best estimate number or rate of events in the state. Any release of personal identifying information is conditioned upon such information remaining confidential. The unauthorized disclosure of any confidential medical or scientific data is a misdemeanor under New Hampshire law. The department is not responsible for any duplication or misrepresentation of surveillance data released in accordance with this guideline.

Birth Condition Occurrence

The data reported by the NH Birth Conditions Program are based on confirmed cases of a birth condition. An infant or fetus may have more than one condition and is counted as a separate “case” for each condition.

Data for birth conditions occurring cases meet the following criteria:

• Born to New Hampshire resident at time of birth
• The infant was live born or, the fetus was stillborn with a gestational age greater than or equal to 20 weeks or with a weight of at least 350 grams.
• The infant or fetus had a structural birth defect that meets diagnostic criteria (NBDPN 6-digit code).
• The diagnosis was made before or at the time the infant reached one year of age.

Data Sources

Hospital discharge data, birth certificates, post-natal care clinics, pathology reports.

• Due to the small numbers of birth defects, caution is advised in the interpretation of conclusions from statistical analyses.
• Misclassification of birth defects may occur through coding errors or vague diagnoses. Quality control measures such as careful abstraction of the medical record minimize this error.
• As medical diagnostic technology has improved, many prenatal and postnatal tests are now performed outside the traditional hospital setting. Prenatal diagnosis enables physicians to identify some birth defects well before the expected date of delivery, and offers women alternatives in the management of their affected pregnancies. These decisions have significant implications for monitoring birth conditions, particularly in the case of pregnancies that are electively terminated. Fetuses that are electively terminated do not routinely receive pathological/diagnostic assessment; therefore it is possible that many birth conditions that occur and are electively terminated are missed.
• New Hampshire resident deliveries and diagnoses that occur out of state are not included at this time. However, the NH BCP is working with border states through a Memorandum of Agreement process to add these data as soon as it is feasible.

Rates

When calculating rates among live born infants and stillbirths, the denominator used is total births. When terminations are included, the total number of terminations for a birth condition is added to the denominator. The general consensus among birth conditions investigators is that the term “prevalence” should be used to describe the rate over time.

Age Specific Prevalence

Age specific prevalence is prevalence calculated for subgroups in a population, such as specific age groups. To interpret specific prevalence, it is important to consider how missing values (unknown maternal ages) may affect the interpretation of the data. For example if age-specific data are presented but only 50% of those data have corresponding maternal ages, then age-specific maternal prevalence rates may not present a true picture of the stratification of the cases among age groups.

Confidence Intervals

A confidence interval is a calculated range of values that describes the true underlying value of a statistic. Most often a 95% confidence interval is calculated. When used with the prevalence statistic, the confidence interval values represent the possible true values of the prevalence. That is to say that prevalence is considered a sample of a given population at a given point in time. The confidence interval provides an idea of the range of values within which the true value is likely to be found. It is used to describe the precision of the prevalence statistic. Confidence intervals will be closer together as the number of cases that they are calculated on increases.

When comparing prevalence rates from one county to another or from the county to the state, it is important to remember that prevalence rates based on counts of cases that are less than 30 produce much larger confidence intervals and are much less stable for use in comparisons. However, an approach recommended by the National Center for Health Statistics to evaluate confidence intervals among groups is to compare the confidence intervals to each other to determine if there is any overlap in values. If they do overlap the difference between them is not statistically significant. If they do not overlap then the difference between them is considered to be statically significant.

For comparisons of confidence intervals where both comparison groups have prevalence rates based on counts of cases that are greater than 30, the recommended approach is to evaluate the confidence intervals using a statistical test to calculate the confidence interval difference. While this calculation can provide more accurately results, using the method discussed above for prevalence based on counts less than 30 can still provide a useable, quick assessment.

* Please contact the NH BCP with any questions regarding comparison of birth conditions data on this website.

Data Confidentiality

The NH Birth Conditions Program (NHBCP) has adopted the NH Department of Health and Human Services, Maternal and Child Health Section Data Confidentiality and Security Policy and will maintain strict standards to protect confidential data. 

Data Requests

Requests for data from the NHBCP must be submitted through Health Statistics and Data Management, Division of Public Health Services, Department of Health and Human Services - http://www.dhhs.state.nh.us/DHHS/HSDM/data-requests.htm.

Birth Condition Categories

Data presented on this website are based on 45 conditions: