Table 7. Results of instrumental variable analysis.

Method *	Birth Length			Birth Weight			Gestational Age
	beta	se	p-value	beta	se	p-value	Beta	se	p-value
Method 1	0.0692	0.0161	1.64E-05	13.4	2.53	1.21E-07	0.280	0.135	0.0385
Method 2	0.0298	0.0214	0.164	5.70	3.30	0.0837	0.387	0.176	0.0276
Method 3	0.0501	0.0236	0.0336	2.47	3.70	0.504	0.440	0.194	0.0234
Method 4	0.0418	0.0257	0.104	0.486	3.96	0.170	0.475	0.209	0.0232

* Method 1 and method 2 use maternal genotype-based genetic score (M) as the instrument variable for maternal height without (method 1) or with (method 2) controlling for fetal genetic score (C). Method 3 utilizes maternal nontransmitted haplotype score (M2) as a valid instrument for maternal height. Method 4 uses maternal nontransmitted haplotype score (M2) as the instrument variable and further adjusts for possible bias due to assortative mating by controlling for maternal and paternal transmitted scores (M1/C1 and C2) as covariates.