The Dutch famine of 1944–45, which affected the western Netherlands, provides a rare opportunity to study the long term consequences of maternal undernutrition in defined stages of gestation (Stein et al., 1975
; Lumey and van Poppel, 1994
). Official rations, which by the end of the famine consisted almost exclusively of bread and potatoes, fell below 900 kcal per day by November 26, 1944, and were as low as 500 kcal per day by April 1945. The famine ceased immediately following liberation. This extraordinary period of deprivation affected fertility, weight gain during pregnancy and infant size at birth (Stein et al., 1975
). The reduction in fertility was greater among manual compared to the non-manual occupational classes (Stein et al., 1975
). The decline in mean birth weight of 300 g was restricted to exposure to maternal undernutrition during the third trimester (Smith, 1947
; Stein et al., 1975
; Stein et al., 2004b
). Long term consequences of gestational exposure to famine have been reported for adiposity (Ravelli et al., 1976
; Ravelli et al., 1999; Stein et al., 2007
), blood pressure (Roseboom et al., 2001
; Stein et al., 2006
), and serum lipids (Roseboom et al., 2000
; Lumey et al., 2009
). It has also been suggested that women (but not men) exposed to famine early in gestation have enhanced reproductive fitness (Painter et al., 2008
Population source and tracing
We identified 3307 live-born singleton births at three institutions in famine-exposed cities (the midwifery training schools in Amsterdam and Rotterdam and the university hospital in Leiden) (Lumey at al., 2007
). We selected all 2417 births between February 1, 1945 and March 31, 1946 (infants whose mothers were exposed to the famine during or immediately preceding that pregnancy) and a sample of 890 births from 1943 and 1947 as hospital time controls (infants whose mothers did not experience famine immediately before or during this pregnancy). The sample of births in 1943 and 1947 included an equal number of births for each month, allocated across the three institutions according to their size.
Names and addresses at birth for these 3307 infants were provided to the Population Register in the municipality of birth with a request for tracing to their current address. 308 (9%) were reported to have died in the Netherlands and 275 (8%) to have emigrated. The Population Registry in Rotterdam declined to trace 130 individuals born out of wedlock and for 294 subjects (9%) a current address could not be located. Address information was obtained for 2300 individuals (70% of the birth series). The proportion of individuals identified as deceased was highest among births in 1943 (10.4%) and lowest among births in 1947 (6.0%). Other reasons for a failure to locate a current address differed little by year of birth or period of exposure to famine. Participants traced to a current address were similar to those who had died, emigrated, or had not been located with respect to birth weight, or length, placental weight, maternal age at delivery, and birth order (Lumey et al., 2007
A letter of invitation signed by the current director of the institution in which they were born was sent to these 2300 individuals, together with a brochure describing the study and a response card. We mailed one reminder letter to non-responders. Initially, our study design called for the recruitment of same-sex sibling pairs only, and the lack of an available sibling was a reason for ineligibility. We received some reply to 58% of the initial letters and to 44% of the reminder letters; 347 individuals (20% of 1767 respondents) expressed willingness to participate together with a sibling. None of the siblings was included in the hospital birth series. Among the 1415 who responded but declined, 951 (67%) reported not having a same-sex sibling available for study. To increase the number of study subjects, we recontacted these 951 individuals, 381 of whom expressed willingness to participate. A higher positive response to our letters from women compared to men (36% vs. 29% overall) was consistent across all exposure categories.
We conducted telephone interviews, followed by a clinical examination at the Leiden University Medical Center. The standardized telephone interview (n=1031 completed; 718 from the birth series and 313 siblings) took approximately one hour. The clinical examination took approximately four hours (n=971 completed; 658 from the birth series and 313 siblings). All study protocols were approved by the Human Subjects Committees of all participating institutions. Study participants provided oral consent at the start of the telephone interview and written informed consent at the start of the clinical examination. All data were collected between 2003 and 2005.
Among the 2300 persons who were invited to join the study, we found no significant differences between those interviewed to those who were not in mean birth weight or length, placental weight, maternal age at delivery, or birth order (Lumey et al., 2004). Response to our invitation, however, was lower for those born in 1947 (25%) compared to all others (35%). Eleven percent of those who were interviewed lived within 5 km of the examination site, versus 10% of those who were not interviewed, and 34% of those interviewed lived more than 45 km from the examination site versus 29% of those who were not interviewed.
Measurement of digit lengths
All examiners were research nurses and were trained for this study by one of us (HSK). Examiners measured 2D and 4D of both hands using a sliding caliper (VWR model 3415, West Chester PA) that was calibrated daily. Briefly, after removing rings and washing the hands, the study participant sat across a table from the examiner with the right elbow resting on the tabletop and the right palm facing upwards at about 45 degrees. The examiner identified the finger’s basal crease as the major crease at the base of the digit that is proximal (nearest) to the palm. The participant was asked to extend the second finger to its full length. The fixed jaw of the caliper was placed on the on the mid-point of the basal crease. The sliding jaw of the caliper was extended past the end of the finger, then retracted until it lay gently at the midline distal tip of the fingertip skin and the digital readout was recorded to the nearest 0.01 mm. The measurement was then repeated for the fourth finger on the same hand, after which both fingers were measured again using the same protocol. After measuring 2D and 4D on the right hand, the protocol was repeated for the left hand. After collecting all 4 finger lengths in duplicate, finger(s) for which the measurements were discrepant by > 1.00 mm were measured two more times. For each finger we calculated the average of the measurements obtained, and we calculated the 2D:4D ratio as 2D divided by 4D.
We assessed handedness based on the response to three questions regarding preference for writing, dealing cards, and opening a bottle. Each question had a 1–3 response (left=1, either=2, right=3). We summed the responses, and categorized individuals scoring 7 or more as right handed, those scoring 6 points as ambidextrous, and those scoring 3–5 points as left handed.
Information on schooling, smoking and alcohol intake were obtained by interview.
Anthropometric measures (height, weight, sitting height, and the waist, hip, supine sagittal abdominal diameter (SAD) and mid-thigh circumferences (MTC)) were obtained in duplicate during the clinic visit using standard protocols (Stein et al., 2007
). We computed the body mass index (BMI; kg/m2
) as an overall measure of adiposity, the ratio of leg length to trunk length as a measure of linear proportionality, and the waist-hip ratio (WHR) and the ratio of the SAD to the MTC as measures of body fat distribution.
Exposure to famine
We used the date of last menstrual period (LMP) as noted in the hospital records to define the start of gestation unless it was missing or implausible. In those cases we inferred the LMP date from annotations on the birth record (e.g., a notation of ‘term birth’) or estimated gestational age from birth weight and date of birth, using cut-points from tables of gender-, parity- and birth weight-specific gestational ages from the combined birth records of the Amsterdam midwives school (1948–1957) and the University of Amsterdam Obstetrics Department (1931–1965) (Kloosterman, 1970
). For each infant the most consistent and plausible estimate of gestation was selected and used together with date of birth to infer the LMP date.
We characterized exposure to famine during gestation by determining the gestational ages (in weeks after the LMP) during which the mother was exposed to an official ration of <900 kcal per day, namely between November 26, 1944, and May 12, 1945. We considered the mother exposed in gestational weeks 1–10, 11–20, 21–30, or 31-delivery if these gestational time windows were entirely included in this period. Thus, pregnancies with LMP’s between November 26, 1944, and March, 4, 1945, were exposed in weeks 1–10; between September 18, 1944 and December 24, 1944 in weeks 11–20; between July 10, 1944, and October 15, 1944, in weeks 21–30; and between May 2, 1944 and August 24, 1944, in weeks 31 through delivery. By these definitions, a participant could have been exposed to famine during at most two adjacent 10-week periods. Individuals exposed in at least one of the 10-week periods were considered to have had any gestational famine exposure. Individuals with LMP between February 3, 1945 and May 11, 1945 were considered to have had peri-conceptional exposure as their mother had been exposed to famine for at least 10 weeks immediately prior to the estimated date of conception.
We computed means and distributions, as appropriate. We computed the differences and correlations among 2D, 4D and the 2D:4D ratio between hands, and between members of the sibling pairs. We assessed the association of 2D, 4D and the 2D:4D ratio with handedness using analysis of variance.
We computed mean 2D and 4D as the average of the respective values across hands; where data for one hand was missing, we used the value for the other hand. We assessed the association of mean 2D, 4D and the 2D:4D ratio with gender and anthropometric measures using analysis of variance and correlation methods.
We assessed the differences in mean digit lengths attributable to exposure to famine using linear regression. In models focusing on any exposure to famine, the variables ‘maternal exposure to famine prior to conception’ and ‘exposure to famine during any 10-week period of gestation’ were entered simultaneously. In models focusing on exposure in defined periods, all four 10-week periods were entered as a set together with the term for exposure prior to conception and the overall significance of the set was tested using a 5 degree of freedom Wald Chi-square test. We examined additive interactions with gender. As there was no evidence of heterogeneity by gender (as defined by a p-value <0.05 for the interaction term) we present gender-pooled results throughout. We controlled for age at assessment (linear and squared terms), gender and the examiner in all models.
All statistical analyses were conducted with Stata software version 8.0 (Stata Inc, College Station TX). The two populations of controls were combined into a single reference group. We controlled for clustering at the family level using the cluster( ) option within Stata, which computes robust estimates using the Huber-White estimator. We report estimates and associated 95 percent confidence intervals. Statistical significance was declared at p<0.05.