A conceptual framework of the impact of maternal early life drought exposure on newborn size in Malawi

Figures & data

Figure 1. Macro-level external pressures on household food security and impacts (1981–1992)

Source: Adapted by Author from Kalkuhl et al. (2013)

Figure 2. Conceptual framework at the micro-level (intergenerational effects of maternal early life adversity on newborn size in rural Malawi)

Source: Adapted by Author from WHO (2013)

Figure 3. Study participants loss to follow-up

Table 1. Characteristics of study population by maternal non-drought exposure or maternal drought exposure in early life

Characteristics	Maternal non-Exposure to drought [0–5 yr]	Maternal Exposure [0–2 yr]	Maternal Exposure[3–5 yr]
	n [mean: range] n [count: %]	n [mean: range] n [count: %]	n [mean: range] n [count: %]
Infant sex [girl]	397 [200: 50.38]	378 [200: 52.91]	439 [220: 50.11]
Maternal age [yr]	418 [23: 14, 49]	391 [25.0: 18–40]	453 [26.9: 16–38]
Maternal height [cm]	418 [155: 139, 171]	389 [156: 132–171]	389 [156: 141,175]
Maternal BMI [kg/m^2]	417 [21.78: 16.10–30.65]	387 [22.12: 16.63–32.98]	450 [22.45: 16.26–37.81]
Marital status [married]	418 [349: 83.49]	391 [346: 88.49]	453 [420: 92.72]
Maternal education [yr]	411 [3.8: 0–12]	383 [4.0: 0–12]	449 [4.0: 0–12]
Head of household [mother]	418 [29: 6.94]	391 [22: 5.63]	453 [33: 7.28]
HH food insecurity access scale [0–10]	412 [5.01: 0, 27]	382 [5.04: 0, 27]	443 [4.74: 0, 24]
HH asset index Z score [SD]	409 [−0.93: −0.73, 3.39]	385 [−0.7: −0.73, 3.29]	446 [0.10: −0.73, 3.29]
Primiparity [yes]	418 [195: 46.65]	390 [48: 12.31]	429 [23: 5.09]
Normal [vs. “at risk”] pregnancy by age[At risk (< 18 yr or ≥ 35 yr)]	418 [192: 45.93]	386 [5: 1.28]	453 [34: 7.51]

Table 2. Subsequent infant birth outcomes by maternal exposure to drought and by age groups

Outcomes	Never exposed at age 0–5 yr (Excluding in utero exposure)	Exposure at age 0–5 yr (1981/82)	Exposure at age 0–5 yr (1987/88)	Exposure at age 0–5 yr (1992/93)	Exposure at age 0–2 yr	Exposure at age 3–5 yr
Infant LAZ^a Mean SD (n)	−1.048 1.125 (844)	−1.013 1.164 (156)	−0.835 1.096 (262)	−1.015 1.082 (304)	−0.899 1.068 (333)	−0.992 1.139 (389)
Infant WAZ^b Mean SD (n)	−0.641 1.038 (852)	−0.626 –0.587 (157)	−0.385 1.083 (266)	−0.591 0.968 (304)	−0.610 1.009 (334)	−0.519 1.044 (393)
Mean Imputed BWT^c Mean SD (n)	2942.108 452.048 (923)	2947.383 488.081 (168)	3027.244 456.898 (292)	2969.268 428.415 (303)	3009.975 432.519 (362)	2965.826 468.520 (431)

^aLength-for-age was calculated using the WHO 2006 growth standards (WHO Multicentre Growth Reference Study Group, 2006)

^bWeight-for-age was calculated using the WHO 2006 growth standards (WHO Multicentre Growth Reference Study Group,2006) .

^cBWT—birthweight

Table 3. Regressions for infant LAZ, infant WAZ, and BWT with maternal exposure to drought (Age 0–5 yr) and prenatal supplements

Variables	(1) Expanded Model: LAZ	(2) Expanded Model: WAZ	(3) Expanded Model: Imputed BWT
Drought exposure in 1981/82# IFA	−0.100	−0.000	6.593
	(−0.527, 0.327)	(−0.383, 0.383)	(−148.096, 161.282)
Drought exposure in 1987/88# IFA	0.315†	0.360**	54.661
	(−0.030, 0.659)	(0.033, 0.686)	(−75.446, 184.769)
Drought of exposure in 1992/93# IFA	0.165	0.285†	106.607
	(−0.172, 0.501)	(−0.029, 0.599)	(−21.894, 235.109)
Non exposure# MMN^4	0.186	0.181	28.212
	(−0.131, 0.502)	(−0.116, 0.479)	(−89.556, 145.981)
Non exposure# LNS^b	0.403***	0.372**	125.900**
	(0.099, 0.708)	(0.053, 0.691)	(2.901, 248.899)
Drought exposure in 1981/82# MMN	0.097	−0.004	11.046
	(−0.431, 0.624)	(−0.473, 0.466)	(−201.432, 223.524)
Drought exposure in 1981/82# LNS	−0.218	−0.199	−136.802
	(−0.816, 0.379)	(−0.747, 0.350)	(−357.689, 84.085)
Drought exposure in 1987/88# MMN	−0.252	−0.188	65.352
	(−0.713, 0.208)	(−0.624, 0.249)	(−101.413, 232.117)
Drought exposure in 1987/88# LNS	−0.482**	−0.390*	−66.503
	(−0.923, −0.041)	(−0.830, 0.050)	(−246.306, 113.301)
Drought exposure in 1992/93# MMN	−0.113	−0.232	−37.918
	(−0.543, 0.318)	(−0.632, 0.169)	(−206.689, 130.853)
Drought exposure in of 1992/93# LNS	−0.487**	−0.488**	−175.820**
	(−0.906, −0.068)	(−0.901, −0.076)	(−339.850, −11.791)
Child sex (girl)	0.116*	0.038	−85.498***
	(−0.020, 0.252)	(−0.091, 0.167)	(−139.293, −31.704)
Maternal education	0.005	0.008	−2.011
	(−0.019, 0.029)	(−0.013, 0.030)	(−11.295, 7.273)
Maternal BMI	0.022	0.032**	15.594***
	(−0.005, 0.050)	(0.006, 0.059)	(4.902, 26.286)
Marital status (married)	−0.106	0.032	−24.611
	(−0.347, 0.135)	(−0.193, 0.256)	(−110.743, 61.522)
Maternal height	0.052***	0.042***	18.250***
	(0.038, 0.065)	(0.029, 0.055)	(13.257, 23.242)
Head of household (mother)	−0.367*	−0.456***	−119.346*
	(−0.738, 0.004)	(−0.798, −0.114)	(−255.881, 17.189)
HH food insecurity access scale	0.008	0.015*	4.479
	(−0.009, 0.024)	(−0.001, 0.030)	(−1.657, 10.615)
HH asset index Z score	0.020	0.053	5.792
	(−0.066, 0.105)	(−0.028, 0.134)	(−28.530, 40.115)
Primiparous	−0.317***	−0.363***	−119.744***
	(−0.504, −0.130)	(−0.538, −0.187)	(−193.549, −45.938)
Normal (vs. “at risk”) pregnancy by age	0.239**	0.043	40.073
Constant	−9.898***	−8.172***	−261.472
	(−12.148, −7.647)	(−10.229, −6.115)	(−1,048.719, 525.775)
N	980	991	1,074
R-squared	0.119	0.113	0.101
F	5.998	6.064	6.345
Adjusted R-squared	0.0995	0.0939	0.0831

Notes:

Outcomes: LAZ—length-for-age Z score, WAZ—weight-for-age Z score, BWT—birthweight

Prenatal supplements: LNS—lipid-based nutrient supplement, MMN—multiple micronutrient supplement, IFA—iron-folic acid

HH—household

Confidence intervals (CI): 95% CI in parentheses (lower bound, upper bound)

Statistical significance (p-values): †p < 0.1, *p < 0.05, **p < 0.01

Table 4. Regressions for infant LAZ, infant WAZ, and imputed infant B/Weight with early life maternal exposure to drought (Age 0–2 yr and 3–5 yr) and prenatal supplements

Variables	(1) Expended Model: LAZ	(2) Expanded Model: WAZ	(3) Expanded Model: Imputed B/Weight
Drought exposure at age 0–2 yr#IFA	0.082	0.251*	40.033
	(−0.238, 0.402)	(−0.046, 0.548)	(−77.913, 157.979)
Drought exposure at age 3–5 yr#IFA	0.154	0.287*	43.839
	(−0.163, 0.471)	(−0.002, 0.576)	(−67.671, 155.350)
Non exposure#MMN^5	0.110	0.214	9.083
	(−0.178, 0.397)	(−0.059, 0.487)	(−98.255, 116.420)
Non exposure#LNS	0.311**	0.421***	135.094**
	(0.005, 0.618)	(0.120, 0.722)	(19.875, 250.313)
Drought exposure at age 0–2 yr#MMN	0.151	−0.087	62.945
	(−0.254, 0.556)	(−0.466, 0.292)	(−93.710, 219.599)
Drought exposure at age 0–2 yr#LNS	−0.316	−0.429**	−179.687**
	(−0.742, 0.110)	(−0.849, −0.010)	(−348.050, −11.324)
Drought exposure at age 3–5 yr#MMN	−0.169	−0.365*	8.300
	(−0.582, 0.245)	(−0.749, 0.018)	(−146.947, 163.548)
Drought exposure at age 3–5 yr#LNS	−0.294	−0.496**	−114.380
	(−0.701, 0.112)	(−0.879, −0.113)	(−266.005, 37.245)
Child sex (girl)	0.117*	0.035	−83.153***
	(−0.018, 0.253)	(−0.093, 0.162)	(−136.402, −29.903)
Maternal education	0.005	0.009	−1.817
	(−0.019, 0.029)	(−0.013, 0.031)	(−10.929, 7.294)
Maternal BMI	0.023	0.032**	15.037***
	(−0.005, 0.050)	(0.006, 0.058)	(4.461, 25.614)
Marital status (married)	−0.084	0.051	−26.725
	(−0.324, 0.155)	(−0.170, 0.272)	(−111.957, 58.508)
Maternal height	0.053***	0.042***	18.280***
	(0.039, 0.066)	(0.030, 0.055)	(13.340, 23.219)
Head of household (mother)	−0.369*	−0.465***	−127.807*
	(−0.739, 0.002)	(−0.804, −0.125)	(−263.357, 7.743)
HH food insecurity access scale	0.006	0.013*	4.172
	(−0.010,—0.023)	(−0.002,—0.028)	(−1.945,—10.289)
HH asset index Z score	0.015	0.047	3.634
	(−0.071, 0.100)	(−0.036, 0.129)	(−30.992, 38.260)
Primiparous	−0.296***	−0.360***	−116.248***
	(−0.484, −0.108)	(−0.537, −0.183)	(−193.436, −39.060)
Normal (vs. “at risk”) pregnancy by age	0.211**	0.060	60.150
	(0.006, 0.415)	(−0.130, 0.250)	(−15.070, 135.370)
constant	−10.017***	−8.271***	−250.759
	(−12.289, −7.746)	(−10.329, −6.213)	(−1,036.422, 534.904)
N	980	991	1,074
R-squared	0.115	0.112	0.100
F	6.748	7.131	7.588
Adjusted R-squared	0.0987	0.0957	0.0842

Notes:

Outcomes: LAZ—length-for-age Z score, WAZ—weight-for-age Z score, BWT—birthweight

Prenatal supplements: LNS—lipid-based nutrient supplement, MMN—multiple micronutrient supplement, IFA—iron-folic acid

HH—household

Confidence intervals (CI): 95% CI in parentheses (lower bound, upper bound)

Statistical significance (p-values): †p < 0.1, *p < 0.05, **p < 0.01

Table 5. Sensitivity analysis for regressions on infant LAZ, infant WAZ, and B/Weight with early life maternal exposure to drought (Age 0–5 yr) and prenatal supplements

Variables	(1) Expended Model: LAZ	(2) Expanded Model: WAZ	(3) Expanded Model: Imputed B/Weight
Drought exposure in 1981/82# IFA	-0.229	-0.085	-15.305
	(-0.694, 0.237)	(-0.503, 0.334)	(-180.962, 150.351)
Drought exposure in 1987/88# IFA	0.425*	0.474**	88.896
	(0.035, 0.815)	(0.117, 0.831)	(-63.828, 241.620)
Drought of exposure in 1992/93# IFA	0.197	0.242	113.420
	(-0.178, 0.573)	(-0.105, 0.588)	(-24.108, 250.947)
Non exposure# MMN^a	0.171	0.179	26.560
	(-0.145, 0.486)	(-0.119, 0.476)	(-91.415, 144.536)
Non exposure# LNS^b	0.396*	0.364*	123.720*
	(0.092, 0.699)	(0.043, 0.684)	(0.158, 247.282)
Drought exposure in 1981/82# MMN	0.028	-0.018	-28.830
	(-0.548, 0.604)	(-0.535, 0.499)	(-263.333, 205.674)
Drought exposure in 1981/82# LNS	0.029	-0.059	-87.829
	(-0.587, 0.645)	(-0.621, 0.503)	(-312.162, 136.504)
Drought exposure in 1987/88# MMN	-0.366	-0.305	24.651
	(-0.860, 0.128)	(-0.762, 0.151)	(-162.298, 211.600)
Drought exposure in 1987/88# LNS	-0.628*	-0.482*	-81.123
	(-1.123, -0.133)	(-0.953, -0.010)	(-287.590, 125.343)
Drought exposure in 1992/93# MMN	-0.163	-0.201	-30.268
	(-0.644, 0.317)	(-0.650, 0.248)	(-210.055, 149.520)
Drought exposure in of 1992/93# LNS	-0.478*	-0.415†	-177.674*
	(-0.939, -0.018)	(-0.864, 0.035)	(-352.909, -2.439)
Child sex (girl)	0.167*	0.052	-61.298*
	(0.018, 0.315)	(-0.088, 0.193)	(-120.463, -2.133)
Maternal education	0.010	0.011	-2.163
	(-0.016, 0.036)	(-0.013, 0.034)	(-12.636, 8.309)
Maternal BMI	0.022	0.026†	14.732*
	(-0.009, 0.052)	(-0.004, 0.055)	(3.038, 26.426)
^aNotes:^a,bThe base category was non exposure to drought interacted with IFA (Non exposure#IFA)
Marital status (married)	-0.243†	-0.040	-37.851
	(-0.507, 0.021)	(-0.272, 0.192)	(-131.693, 55.992)
Maternal height	0.055**	0.046**	20.571**
	(0.040, 0.070)	(0.032, 0.060)	(14.905, 26.238)
Head of household (mother)	-0.441*	-0.471*	-102.863
	(-0.826, -0.056)	(-0.832, -0.109)	(-248.461, 42.735)
HH food insecurity access scale	0.010	0.015†	5.330
	(-0.009, 0.028)	(-0.002, 0.032)	(-1.425, 12.084)
HH asset index Z score	0.010	0.069	2.286
	(-0.081, 0.100)	(-0.017, 0.154)	(-35.392, 39.963)
Primiparous	-0.412**	-0.393**	-109.087**
	(-0.617, -0.207)	(-0.591, -0.196)	(-188.901, -29.272)
Normal (vs. “at risk”) pregnancy by age	0.211†	0.012	38.716
	(-0.018, 0.439)	(-0.197, 0.221)	(-46.096, 123.529)
Constant	-10.249**	-8.579**	-613.767
	(-12.723, -7.775)	(-10.800, -6.358)	(-1,511.601, 284.067)
N	810	820	889
R-squared	0.145	0.133	0.111
F	6.578	6.127	5.451
Adjusted R-squared	0.122	0.110	0.0890

Notes:

Outcomes: LAZ - length-for-age Z score, WAZ - weight-for-age Z score, BWT - birthweight

HH - household

Confidence intervals (CI): 95% CI in parentheses

Statistical significance (p-values): †p < 0.1, *p < 0.05, **p < 0.01

Table 6. Sensitivity Analysis for Regressions on Infant LAZ, Infant WAZ, and B/Weight with Early Life Maternal Exposure to Drought (Age 0-2 yr and 3-5 yr) and Prenatal Supplements

Variables	(1) Expended Model: LAZ	(2) Expanded Model: WAZ	(3) Expanded Model: Imputed B/Weight
Drought exposure at age 0-2 yr#IFA	0.422*	0.239	122.896†
	(0.039, 0.805)	(-0.144, 0.622)	(-17.331, 263.124)
Drought exposure at age 3-5 yr#IFA	0.045	0.235	47.624
	(-0.296, 0.386)	(-0.074, 0.543)	(-79.733, 174.982)
Non exposure# MMN	0.177	0.184	27.700
	(-0.138, 0.492)	(-0.114, 0.481)	(-90.004, 145.404)
Non exposure# LNS	0.396*	0.364*	124.672*
	(0.093, 0.700)	(0.044, 0.685)	(1.216, 248.127)
Drought exposure at age 0-2 yr#MMN	-0.594*	-0.339	-125.272
	(-1.079, -0.109)	(-0.819, 0.141)	(-311.768, 61.225)
Drought exposure at age 0-2 yr#LNS	-0.457†	-0.182	-24.983
	(-0.965, 0.051)	(-0.671, 0.306)	(-214.426, 164.461)
Drought exposure at age 3-5 yr#MMN	0.003	-0.132	36.386
	(-0.424, 0.429)	(-0.520, 0.256)	(-125.121, 197.893)
Drought exposure at age 3-5 yr#LNS	-0.347	-0.395†	-146.397†
	(-0.763, 0.068)	(-0.802, 0.011)	(-311.353, 18.558)
Child sex (girl)	0.171*	0.051	-54.973†
	(0.023, 0.319)	(-0.090, 0.191)	(-113.811, 3.866)
Maternal education	0.011	0.012	-1.756
	(-0.015, 0.037)	(-0.011, 0.036)	(-11.981, 8.470)
Maternal BMI	0.018	0.023	13.786*
	(-0.013, 0.048)	(-0.006, 0.052)	(2.422, 25.150)
Marital status (married)	-0.207	-0.012	-29.946
	(-0.469, 0.055)	(-0.242, 0.218)	(-123.630, 63.738)
Maternal height	0.054**	0.046**	20.133**
	(0.039, 0.069)	(0.032, 0.059)	(14.571, 25.696)
Head of household (mother)	-0.421*	-0.465*	-115.115
	(-0.803, -0.038)	(-0.828, -0.101)	(-258.114, 27.884)
HH food insecurity access scale	0.008	0.014	4.731
	(-0.011, 0.027)	(-0.003, 0.031)	(-1.962, 11.424)
HH asset index Z score	0.000	0.053	0.116
	(-0.089, 0.090)	(-0.033, 0.139)	(-37.514, 37.745)
Primiparous	-0.407**	-0.394**	-110.796**
	(-0.604, -0.210)	(-0.587, -0.201)	(-188.898, -32.694)
Normal (vs. “at risk”) pregnancy by age	0.206†	0.011	41.570
	(-0.021, 0.433)	(-0.196, 0.219)	(-42.306, 125.446)
Constant	-10.077**	-8.519**	-533.807
	(-12.500, -7.654)	(-10.702, -6.336)	(-1,411.749, 344.136)
N	810	820	889
R-squared	0.143	0.126	0.113
F	8.008	7.001	7.256
Adjusted R-squared	0.123	0.106	0.0947

Notes:

Outcomes: LAZ - length-for-age Z score, WAZ - weight-for-age Z score, BWT - birthweight

LNS - lipid-based nutrient supplement, MMN - multiple micronutrient supplement, IFA - iron-folic acid

HH - household

Confidence intervals (CI): 95% CI in parentheses (lower bound, upper bound)

Statistical significance (p-values): †p < 0.1, *p < 0.05, **p < 0.01

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